Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SYSTEMS AND METHODS TO PLACE ONE OR MORE LEADS IN
MUSCLE FOR PROVIDING ELECTRICAL STIMULATION TO TREAT
PAIN
10
20
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Field of Invention
This invention relates to systems and methods for
percutaneously placing one or more leads in muscle for
providing electrical stimulation to a motor point(s) in
the muscle to treat the perception of pain.
Background of the Invention
The electrical stimulation of nerves, often afferent
nerves, to indirectly affect the stability or performance
of a physiological system can provide functional and/or
therapeutic outcomes, and has been used for activating
target nerves to provide therapeutic relief of pain.
While existing systems and methods have been shown
to provide remarkable benefits to individuals requiring
therapeutic relief, many issues and the need for -
improvements still remain.
Many techniques have been developed to treat pain,
but all of them are ultimately insufficient.
Non-narcotic analgesics, such as acetaminophen or
non-steroidal anti-inflammatory drugs (NSAIDS), have
relatively minor side effects and are commonly used for
several types of pain. However, they are rarely
sufficient in managing moderate to severe chronic pain
(Sherman et al. 1980; Loeser 2001a; Rosenquist and Haider
2008).
The use of narcotic analgesics, such as N-methyl-D-
aspartate (NDMA) antagonists, has shown only minor
success with inconsistent results. Narcotics carry the
risk of addiction and side effects, such as nausea,
confusion, vomiting, hallucinations, drowsiness,
dizziness, headache, agitation, and insomnia.
Psychological strategies, such as biofeedback and
=psychotherapy, may be used as an adjunct to other
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therapies but are seldom sufficient, and there are few
studies demonstrating efficacy.
Electrical stimulation systems have been used for
the relief of pain, but widespread use of available
systems is limited.
There exist both external and implantable devices
for providing electrical stimulation to activate nerves
and/or muscles to provide therapeutic relief of pain.
These "neurostimulators" are able to provide treatment
and/or therapy to individual portions of the body. The
operation of these devices typically includes the use of
one or more electrodes placed either on the external
surface of the skin and/or a surgically implanted
electrode. In most cases, surface electrode(s), cuff-
style electrode(s), paddle-style electrode(s), spinal
column electrodes, and/or percutaneous lead(s) having one
or more electrodes may be used to deliver electrical
stimulation to the select portion of the patient's body.
Transcutaneous electrical nerve stimulation (TENS)
has been cleared by the FDA for treatment of pain. TENS
systems are external neurostimulation devices that use
electrodes placed on the skin surface to activate target
nerves below the skin surface. TENS has a low rate of
serious complications, but it also has a relatively low
(i.e., less than 2596) long-term rate of success.
Application of TENS has been used to treat pain
successfully, but it has low long-term patient
compliance, because it may cause additional discomfort by
generating cutaneous pain signals due to the electrical
stimulation being applied through the skin, and the
overall system is bulky, cumbersome, and not suited for
long-term use (Nashold and Goldner 1975; Sherman 1980;
Finsen et al. 1988).
In addition, several clinical and technical issues
associated with surface electrical stimulation have
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prevented it from becoming a widely accepted treatment
method. First, stimulation of cutaneous pain receptors
cannot be avoided resulting in stimulation-induced pain
that limits patient tolerance and compliance. Second,
electrical stimulation is delivered at a relatively high
frequency to prevent stimulation-induced pain, which
leads to early onset of muscle fatigue in turn preventing
patients from properly using their arm. Third, it is
difficult to stimulate deep nerves and/or muscles with
surface electrodes without stimulating overlying, more
superficial nerves and/or muscles resulting in unwanted
stimulation. Finally, clinical skill and intensive
patient training is required to place surface electrodes
reliably on a daily basis and adjust stimulation
parameters to provide optimal treatment. The required
daily maintenance and adjustment of a surface electrical
stimulation system is a major burden on both patient and
caregiver.
Spinal cord stimulation (SCS) systems are FDA
approved as implantable neurostimulation devices marketed
in the United States for treatment of pain. Similar to
TENS, when SCS evokes paresthesias (generally described
as a comfortable tingling sensation) that cover the
region of pain, it confirms that the location of the
electrode and the stimulus intensity should be sufficient
to provide pain relief and pain relief can be excellent
initially, but maintaining sufficient paresthesia
coverage is often a problem as the lead migrates along
the spinal canal (Krainick et al. 1980; Sharan et al.
2002; Buchser and Thomson 2003).
Spinal cord stimulation is limited by the invasive
procedure and the decrease in efficacy as the lead
migrates. When it can produce paresthesias in the region
of pain, spinal cord stimulation is typically successful
initially in reducing pain, but over time the paresthesia
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coverage and pain reduction is often lost as the lead
migrates away from its target (North et al. 1991;
Andersen 1997; Loeser 2001a).
Lead migration is the most common complication for
spinal cord stimulators occurring in up to 45-88% of the
cases (North et al. 1991; Andersen 1997; Spincemaille et
al. 2000; Sharan et al. 2002). When the lead migrates,
the active contact moves farther from the target fibers
and loses the ability to generate paresthesias in the
target area. SCS systems attempt to address this problem
by using leads with multiple contacts so that as the lead
travels, the next contact in line can be selected to be
the active contact.
Peripheral nerve stimulation may be effective in
reducing pain, but it previously required specialized
surgeons to place cuff- or paddle-style leads in intimate
contact with or around the nerves in a time consuming
procedure.
Percutaneous, intramuscular electrical stimulation
for the treatment of post-stroke shoulder pain has been
studied as an alternative to surface electrical
stimulation. A feasibility study (Chae, Yu, and Walker,
2001) and a pilot study (Chae, Yu, and Walker, 2005)
showed significant reduction in pain and no significant
adverse events when using percutaneous, intramuscular
electrical stimulation in shoulder muscles.
While the above mentioned percutaneous electrical
stimulation system overcame some of the barriers of
surface electrical stimulation, it faced some additional
drawbacks having to deal with the placement of multiple
leads in different muscle locations, and then the
containment of these multiple leads during use of the
stimulation system.
As previously described, electrical stimulation has
been used and shown to be effective in treating pain, but
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present methods of implementation have practical limitations
that prevent widespread use. External systems are too
cumbersome, and implanted spinal cord stimulation systems
require complex implantation techniques, and often have problems
of lead migration along the spinal canal, resulting in either
the need for frequent reprogramming or clinical failure.
Peripheral nerve stimulation requires specialized surgeons to
place cuff-or paddle-style leads in intimate contact with or
around the nerves in a time consuming procedure.
It is time that systems and methods for providing
electrical stimulation address not only specific therapeutic
objectives, but also address and improve the quality of life of
the individual requiring the therapy, including a need to treat
pain with minimally-invasive systems and methods that include
intramuscular lead(s) that can be inserted percutaneously into
muscle near a motor point (s), may not require reprogramming
and/or repositioning, and are better adapted to resist migration
within the muscle.
Summary of the Invention
The invention provides systems and methods for
percutaneously placing one or more intramuscular (IM) leads in
muscle for providing electrical stimulation to a motor point(s)
in the muscle to treat the perception of pain.
In a first aspect, this document discloses a use of an
electrical stimulation system to alleviate pain, the electrical
stimulation system comprising a locating lead for percutaneous
placement at multiple locations in a tissue region, the locating
lead being for identifying a motor point, the motor point being
identified when a skeletal muscle twitch is produced when an
electrical stimulation is provided to the locating lead; at
least one intramuscular lead having at least one electrode, the
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at least one electrode being for placement within a skeletal
muscle which is in electrical proximity to the motor point, and
an electrical stimulation device for providing therapeutic
electrical stimulation to the at least one electrode according
to predefined therapeutic electrical stimulation parameters, the
electrical stimulation being for affecting afferent and/or
efferent nerve stimulation within the skeletal muscle without
any functional nerve stimulation involving the skeletal muscle.
In a second aspect, the document discloses a use of a
system of electrical leads and electrical stimulation to
alleviate pain, the system comprising: a first lead for
placement at a first point in electrical proximity to an
identified first motor point of a first muscle, a second lead
for placement at a second point in electrical proximity to an
identified second motor point of a second muscle, a third lead
for placement in electrical proximity to a third point generally
between the first and second points , and an electrical
stimulation device for providing electrical stimulation to the
third lead, the electrical stimulation being for activating the
identified first motor point and the identified second motor
point.
Another aspect of the invention places one or more leads in
a muscle to activate one or more motor points innervating the
muscle in a system for the relief of pain. The systems and
methods optimally allow using a single lead, although it is to
be appreciated that more than one lead(s) may be used, to
activate one or more motor points innervating the muscle.
Another aspect of the invention provides systems and
methods including lead placement procedures that may be
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used for placing a single lead to activate more than one
motor point simultaneously, i.e., a motor point
innervating a muscle A and a motor point innervating a
muscle B simultaneously, (e.g., the middle and posterior
deltoid muscle) in a system for the relief of shoulder
pain, but is not exclusive to this application. The
procedures optimally allow using only a single lead,
although it is to be appreciated that more than one
lead(s) may be used, to activate two motor points of
adjacent muscles optimally.
Yet another aspect of the invention comprises a
method to reduce and/or relieve pain. The method includes
percutaneously placing an intramuscular lead into a
muscle in a region where pain is felt, such that the lead
is in electrical proximity, but not touching, a motor
point within the muscle, and electrically stimulating the
motor point within the muscle where the lead is placed to
reduce and/or relieve the pain in the region where the
pain is felt. The intramuscular lead may include at
least one anchoring member to anchor the lead in the
muscle. Electrically stimulating the motor point may
reduce and/or relieve the pain without any functional
movement or response. The region where the pain is felt
may include the muscle where the intramuscular lead is
placed.
Another aspect of the invention comprises a method
to alleviate pain. The method includes identifying a
tissue region where pain is perceived including skeletal
muscle innervated by a peripheral nerve and including a
motor point, placing at least one intramuscular lead
having at least one electrode within the skeletal muscle
in electrical proximity, but not touching, the motor
point, and applying therapeutic electrical stimulation to
the at least one electrode according to predefined
therapeutic electrical stimulation parameters to affect
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af f erent and/or efferent nerve stimulation within the
skeletal muscle and to provide the therapeutic electrical
stimulation to the motor point to alleviate pain without
any functional nerve stimulation involving the skeletal
muscle.
In one embodiment, the step of identifying the
tissue region may include locating the motor point by
percutaneously placing a first lead and applying the
therapeutic electrical stimulation to the first lead and
adjusting the position of the first lead until a muscle
twitch is observed in the skeletal muscle. The motor
point may be located without any feedback from the
patient.
In an additional aspect of the invention comprises a
method of therapeutically stimulating a motor point of a
peripheral nerve to reduce the perception of pain in a
muscle region innervated by the peripheral nerve, without
stimulating the motor point to produce a functional
response. The method includes percutaneously placing at
least one intramuscular lead having at least one
electrode in the muscle region where the perception of
pain is experienced, and electrically stimulating the
motor point with the at least one electrode to reduce the
perception of pain in the muscle region. Electrically
stimulating the motor point may require evoking a muscle
contraction in the muscle to confirm correct lead
placement. The steps to place the IM lead percutaneously
near the motor point and to evoke a muscle contraction
may be accomplished between about one minute and about
thirty minutes.
An additional aspect of the invention comprises a
method of placing a first lead in electrical proximity to
a first motor point of a first muscle, placing a second
lead in electrical proximity to a second motor point of a
second muscle, placing a third lead in electrical
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proximity to a point generally in-between the first lead
in electrical proximity to the first motor point of the
first muscle and the second lead in electrical proximity
to the second motor point of the second muscle, and
providing electrical stimulation to the third lead to
activate the motor point of the first muscle and the
motor point of the second muscle. The first muscle and
the second muscle may be activated simultaneously, and
the first lead and the second lead may be a different
configuration than the third lead. For example,
the
third lead may be an intramuscular lead and the first
lead and the second lead may be EMG leads.
In one embodiment, the method may include recording
electrical stimulation parameters used to activate the
motor point of the first muscle and/or the motor point of
the second muscle. In another embodiment, the method may
include recording electrical stimulation parameters
provided to the third lead to activate the motor point of
the first muscle and the motor point of the second
muscle. The first muscle may comprise the middle deltoid
muscle, and the second muscle may comprise the posterior
deltoid muscle, and the electrical stimulation applied to
the third lead provides relief of shoulder pain. The
method may include removing the first lead and the second
lead after placing the third lead. The electrical
stimulation applied to the third lead desireably provides
relief of pain to both the first muscle and the second
muscle.
Another aspect of the invention provides systems and
methods for providing therapeutic electrical stimulation
to a muscle region where pain is felt to reduce the
perception of pain in a muscle region. A system may
comprise an intramuscular lead having at least one
electrode, the lead and electrode adapted to be placed
between motor points of at least two muscles, and a pulse
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generator adapted to provide the therapeutic electrical
stimulation to the lead and electrode to therapeutically
stimulate the motor points of the at least two muscles to
reduce the perception of pain in the muscle region. In
one embodiment, the intramuscular lead includes at least
one anchoring member to anchor the lead in the muscle.
The muscle region where pain is felt may comprise the at
least two muscle where the intramuscular lead is placed.
Yet an additional aspect of the invention provides a
system for providing therapeutic electrical stimulation
to a region of pain to reduce the perception of pain.
The system may comprise an intramuscular lead having at
least one electrode, the lead and electrode adapted to be
placed in electrical proximity but not touching a motor
point of a muscle, and a pulse generator adapted to
provide the therapeutic electrical stimulation to the
lead and electrode to therapeutically stimulate the motor
point of the muscle to reduce the perception of pain in
the region of pain. In one embodiment, the pulse
generator may be adapted to provide the therapeutic
electrical stimulation to the lead and electrode to
therapeutically stimulate the motor point of the muscle
to reduce the perception of pain in the muscle without
the generation of paresthesias, although some
paresthesias may be perceived.
In one embodiment, the therapeutic electrical
stimulation is adapted to provide a therapeutic
stimulation function, the therapeutic stimulation
function including a function selected from a group
comprising the treatment of (i) shoulder pain, (ii) arm
pain, (iii) calf pain, (iv) leg pain, (v) neck pain, (vi)
head pain, and (vii) back pain.
Yet an additional aspect of the invention provides
systems and methods, including a method of reducing the
perception of pain in a muscle region, the method
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comprising placing an intramuscular lead in muscle near
but not touching a motor point of the muscle, providing
therapeutic electrical stimulation via the intramuscular
lead to the motor point of the muscle, activating the
motor point of the muscle with the therapeutic electrical
stimulation, and causing the reduction of the perception
of pain in the muscle region where the lead is placed.
The intramuscular lead may be placed percutaneously via
an introducer. The therapeutic electrical stimulation
may be applied without causing the generation of
paresthesias, although some paresthesias may be
perceived. The muscle region where the pain is perceived
may comprise the muscle where the intramuscular lead is
placed.
The therapeutic electrical stimulation may be
applied to target motor points in muscles, the muscles
comprising the posterior, anterior, and/or middle
dletoid, trapezius, erector spinae, gastrocnemius,
occipitailis, gluteus maximus, gluteus medius, iliotibial
band, biceps femoris, adductor magnus, semitendinosus,
gracilis, semimembranosus, sartorius, pectineus, adductor
longus, vastus medialis, vastus lateralis, and rectus
femoris, as non-limiting examples.
Other features and advantages of the inventions are
set forth in the following specification and attached
drawings.
Brief Description of the Drawings
Figs. 1A through 1C are schematic diagrams showing
placement of one or more intramuscular leads to stimulate
one or more motor points.
Fig. 2 is a schematic diagram similar to Figs. 1A
through 1C, showing placement of a single intramuscular
lead to stimulate more than one motor point
simultaneously.
Figs. 3A and 33 are anatomical views of a patient
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utilizing an embodiment of the present invention,
including a percutaneous lead coupled to an external
pulse generator or an implantable pulse generator.
Figs. 4A and 4B are anatomical views of patients
utilizing an embodiment of the present invention to treat
calf pain (Fig. 4A) and neck pain (Fig. 4B).
Figs. 5 and 6 are anatomical views of a patient's
shoulder showing the placement of a needle electrode
placed in proximity to motor point A and a needle
electrode placed in proximity to motor point B.
Fig. 7 is an anatomical view of the shoulder as
shown in Fig. 6, showing a pulse generator coupled to one
needle electrode and to the return electrode so that test
stimulation may be delivered to stimulate the desired
motor point.
Fig. 8 is an anatomical view of the shoulder as
shown in Fig. 6, showing the location at which both
muscle A and muscle B can be activated simultaneously
using one electrode, by placing a needle electrode at the
approximate midpoint between the prior identified
locations of needle electrodes for muscle A and muscle B
respectively.
Fig. 9 is an anatomical view of the shoulder as
shown in Fig. 6, showing the intramuscular lead 12 and
electrode 14 placed percutaneously in the shoulder via an
introducer needle.
Fig. 10 is =an anatomical view of the shoulder as
shown in Fig. 6, showing the percutaneous exit site and
lead 12 covered with a bandage 32, and an additional
bandage 34 is shown to secure the external portion of the
lead 12 (or an extension cable used to couple the lead 12
to the external pulse generator) to the skin.
Figs. 11A and 11B are plan views of a possible
intramuscular lead having one electrode or more than one
electrode for use with the systems and methods of the
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present invention, the lead including one or more
anchoring members.
Figs. 12A and 12B are plan views of another possible
intramuscular lead having one electrode or more than one
electrode for use with the systems and methods of the
present invention, the lead including one or more
anchoring members.
Figs. 13 to 15 show the use of a lead introducer to
percutaneously implant an intramuscular lead in a
targeted muscle region and for connection to a lead
extension.
Fig. 16 is a graphical view of a possible biphasic
stimulus pulse output of the external and/or implantable
pulse generators for use with the system shown in Figs.
3A through 4B.
Fig. 17 is a plan view of a kit packaging the
systems and methods components for use, along with
instructions for use.
Fig. 18 is a plan view of another embodiment of a
kit packaging the systems and methods components for use,
along with instructions for use.
Fig. 19 is a plan view of another embodiment of a
kit packaging the systems and methods components for use,
along with instructions for use.
Description of the Preferred Embodiment
Although the disclosure hereof is detailed and exact
to enable those skilled in the art to practice the
invention, the physical embodiments herein disclosed
merely exemplify the invention which may be embodied in
other specific structures. While the preferred
embodiment has been described, the details may be changed
without departing from the invention, which is defined by
the claims.
Any elements described herein as singular can be
pluralized (i.e., anything described as "one" or "a" can
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be more than one), and pluralized elements may be
singular. Any species element of a genus element can have
the characteristics or elements of any other species
element of that genus. The described configurations,
elements or complete assemblies and methods and their
elements for carrying out the invention, and variations
of aspects of the invention can be combined and modified
with each other in any combination.
The various aspects of the invention will be
described in connection with the placement of one or more
intramuscular leads 12 having one or more electrodes 14,
in muscle, and in electrical proximity to, but not in
intimate contact with, motor points and/or nerves, for
improved recruitment of targeted nerves for therapeutic
purposes, such as for the treatment of pain, including
but not limited to shoulder pain, arm pain, calf pain
(e.g., claudication pain), leg pain, neck pain, head pain
(e.g., migraine), and back pain (e.g., pain related to
failed back surgery syndrome) as non-limiting examples.
That is because the features and advantages that arise
due to the invention are well suited to this purpose.
Still, it should be appreciated that the various aspects
of the invention can be applied to achieve other
objectives as well, and that any known motor point(s) may
be stimulated in accordance with the invention for the
therapeutic purpose of the treatment of pain.
I. Reduction of Pain
The present novel invention provides systems and
methods for the reduction of pain. The systems and
methods of the present invention are adapted to reduce
pain by stimulating a motor point, and/or a target nerve,
of a muscle, i.e., the motor point and/or nerve that
innervate the muscle where the region(s) of pain are
felt. A motor point is known to be a region on or in a
muscle where the application of an electrical stimulation
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will cause the contraction of the muscle. It is to be
appreciated that regions of pain can include any or all
portions of the body, including arms, legs, head, neck,
and torso in both humans and animals.
Motor point stimulation can also be described as
essentially muscle stimulation, wherein an IM lead is
placed near the target motor point in the target muscle
innervated by the target nerve to relieve pain in the
region of pain, which may include the target muscle. The
target muscle is desirably the same muscle in which the
lead is placed. As one non-limiting example, an IM lead
may be placed near the motor points of the deltoid muscle
to relieve pain in the deltoid muscle, i.e., the pain is
felt and relieved in the area where the IM lead is
located. Placement of the lead(s) "near" or "near but
away from" or "in electrical proximity to" or not
touching" the motor point(s) can include, but are not
limited to, one or more lead diameter lengths away from
the motor point(s), although it is to be appreciated that
the lead(s) may be closer in some applications and
farther away in other applications. The lead is
desirably close enough to the motor point to cause muscle
contraction without inducing additional discomfort or
pain. It is to be appreciated that a stimulus intensity
high enough to cause muscle contraction may be beneficial
to aid in the placement of the lead(s), but may not be
required for the therapeutic purpose of the treatment of
pain. For example, a sub-threshold stimulus intensity
(e.g., where no muscle contraction is caused), may be
sufficient for the therapeutic purpose of the treatment
of pain.
There is familiarity with motor point stimulation by
physiatrists who are used to placing needles
superficially near motor points, typically in EMG needle
placement and nerve conduction studies, and physiatrists
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are accustomed to using motor responses to guide needle
placement.
Some motor points, but not all, are located
relatively superficially. This allows for systems and
methods where imaging, such as fluoroscopy or ultrasound,
are not required to place the IM lead for motor point -
stimulation, although either may be used.
Motor point stimulation may require evoking a muscle
contraction to confirm correct lead placement, but does
not require generation of paresthesias (although
possible) or patient feedback of sensation to locate the
lead correctly. The muscle that contracts is the same
muscle in which the IM lead is placed, and may be where
the region(s) of pain are felt.
The patient is not required to give verbal, written,
or other type of feedback or indication of what they feel
as the IM lead is being advanced towards the motor point.
This minimizes patient involvement and simplifies the
procedure for the clinician.
After the IM lead has been correctly positioned, the
patient may indicate sensations during tuning of stimulus
intensity. As non-limiting examples, those sensations
reported by the patient may include first sensation
(minimum stimulus intensity that evokes a sensation),
level of comfort, maximum tolerable sensation, pain,
and/or qualities and/or descriptions of the sensations.
The primary targeted pain area may be, but does not
need to be, proximal to the IM lead. For example, in the
case of shoulder pain, the lead may be placed distal to
(or more peripheral than) the shoulder, meaning that the
area of shoulder pain is in between the IM lead and the
center of the body (e.g., the spinal cord).
Use of the intramuscular lead is intended to relieve
pain by modulating and/or changing one or more
sensations, which is known as therapeutic electrical
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stimulation. This is in stark contrast from previous
uses of an IM lead intended to achieve functional
movement or response (utility), which is known as
functional electrical stimulation or FES. Muscle
contraction is not to be considered a functional movement
or response.
Placement of an intramuscular lead in electrical
proximity to, but not touching, a motor point is
primarily for the purpose of evoking muscle contraction
and is primarily to simplify the lead placement procedure
and to confirm that the stimulus intensity is sufficient
without needing more complicated sensory feedback from
the patient. The combination of the IM lead and the
desired placement makes the systems and methods simpler
and also more robust than prior systems intended to treat
pain. Even if the lead migrates, as long as stimulation
is evoking muscle contraction, the clinician and patient
know that the lead is still sufficiently close to the
motor point and that the stimulus intensity is
sufficiently high.
The muscle contraction(s) confirms that the stimulus
intensity is above a threshold, i.e., is high enough, to
activate the larger A fibers that can "close the gate"
and prevent activity in the smaller C fibers that
transmit nociceptive information from reaching higher
centers in the central nervous system and keep the
patient from feeling the pain. In other words, seeing
the muscle twitch is an indicator that stimulus intensity
is sufficient to provide pain relief.
The muscle contraction(s) may also indirectly
generate additional activation of afferent fibers by
contracting the muscle. For
example, one set of
afferents in the target nerve may be directly activated
by electrical stimulation, e.g., at a location near the
electrode. Action potentials in these afferent fibers
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may be generated by the electrical signals coming
directly from the electrode contact. If the stimulating
frequency is 12 Hz (for example), then these afferent
fibers are being excited and firing at 12 Hz. There
should be approximately a one-to-one ratio between the
stimulating frequency and the rate of afferent action
potentials. Firing of
these afferents due to the
electrical stimulation may be more or less synchronized.
Another set of afferents that innervate the muscle,
such as those that respond to and "sense" muscle
contraction, may be activated by the muscle contraction,
which happened to be evoked by electrical stimulation of
the motor point. These afferents would be similarly
activated if the person chose to repeatedly flex or
contract their muscle, i.e., without electrical
stimulation. This secondary or indirect activation of
afferents may be more natural and/or desynchronized, and
may increase the potential therapeutic effect of pain
relief.
Action potentials in the afferent fibers are
generated by physical signals, e.g., pressure, stretch,
movement, etc., due to muscle contraction. The
stimulating frequency may not correspond to the frequency
with which action potentials are generated in the
afferent fibers. There may likely be a distribution of
the frequencies at which the afferent fibers are
propagating the action potentials. Firing of
the
afferent fibers, due to muscle contraction, may likely be
somewhat desynchronized, similar to what would be
expected during voluntary muscle contraction.
These two sets of afferents may or may not include
=some or all of the same afferents. Since activation of
afferents via electrical stimulation and/or muscle
contraction may be able to provide pain relief, the
systems and methods of the present invention take
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advantage of both, and the combined effect of the direct
and indirect activation of afferents may enhance the
ability to treat the pain.
The present novel invention provides systems and
methods that place percutaneous IM lead(s) 12
appropriately in muscle to electrically activate a motor
point(s) of nerve(s) that carry the pain signal(s). For
example, if there is pain in the deltoid region, e.g.,
shoulder, the systems and methods are well adapted to
stimulate the motor points of the deltoid muscles. If
electrical stimulation activates the motor points
sufficiently at an acceptable intensity, the pain signal
will be reduced. As previously described, the patient
may also feel, but is not required to feel, the
comfortable tingling sensation called a paresthesia in
the same region as their pain. It is to be appreciated
that the sensation could be described with other words
such as buzzing, thumping, etc. Just as the patient can
have pain in a specific body region, electrical
stimulation can evoke paresthesias that the patient also
feels in the specific body region. It is not necessary to
evoke paresthesias in the regions of pain to confirm
correct IM lead placement, and it is possible that pain
relief may be achieved without the patient reporting any
sensation of electrically evoked paresthesias.
As shown in Figs. LA through 2, the systems and
methods are well adapted to activate the motor point of a
muscle by placing a lead 12 with its electrode 14 close,
i.e., in electrical proximity but not touching, to the
motor point (see Fig. 1A). Fig. 1B shows the use of two
leads 12(A) and 12(B), to stimulate motor points in
muscle A and muscle B, respectively. Fig. 1C shows the
use of more than one lead 12, e.g., two leads, to
stimulate the motor point of a muscle. Fig. 2 shows the
use of one lead 12 to stimulate the motor point A of
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muscle A and the motor point B of muscle B. It is to be
appreciated that the intramuscular leads 12 may
incorporate a single electrode 14, or may incorporate
more than one electrode, e.g., four or eight electrodes,
as a non-limiting example.
As previously described, a motor point can be
defined as the location where the innervating nerve
enters the muscle. At that location, the electrical
stimulation intensity required to elicit a full
contraction is at the minimum. Any other location in the
muscle would require more stimulation intensity to elicit
the same muscle contraction.
The ability to insert the IM lead 12 percutaneously
near a motor point simplifies the approach to a quick
(e.g., about 1 to about 5, or 10, or 20, or 30 minute, or
more or less) procedure, such as an out-patient procedure
that can be performed in a standard community-based
clinic, allowing widespread use and providing a
minimally-invasive screening test to determine if
patients will benefit from the systems and methods of the
present invention, including a percutaneous system 10
and/or a fully implanted system 11. Figs. 3A and 3B show
a percutaneous system 10 and a fully implanted system,
respectively, to stimulate one or more motor points in
the shoulder to relieve pain in the shoulder. Fig. 4A
shows the use of a percutaneous system 10 to relieve pain
in the neck region, and Fig. 4B shows the use of a
percutaneous system 10 to relieve pain in the calf
region.
The systems and methods of the present invention are
- well suited to place a percutaneous IM lead 12 near a
motor point(s) with a quick procedure to generate
electrically a therapeutic pulse train to reduce the
patients' pain, without any functional stimulation or
paresthesia.
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In a percutaneous system 10, the lead 12 may be
percutaneously placed near the motor point and exit at
the skin puncture site 16 and coupled to an external
pulse generator 26 (see Fig. 3A). The percutaneously
placed IM lead 12 and external pulse generator 26 may
provide a screening test function to confirm pain relief
of the painful areas. If the screening test is
successful, the patient may proceed to a home-trial
(e.g., a day, week, month, or year, or more or less) to
determine if pain relief can be sustained in the home
environment. If either the screening test or home trial
is unsuccessful, the IM lead 12 may be quickly and easily
removed. It is to be appreciated that a home-trial is not
a requirement for either the percutaneous system or a
fully implanted system.
However, if the screening test and/or home-trial are
successful, the patient's percutaneous system may be
converted into a fully implanted system 11 by replacing
the external pulse generator 26 with an implantable pulse
generator 28 that is implanted in a convenient area
(e.g., the subclavicular area), and coupling a new
sterile lead 12, or a sterile lead extension, to the
implantable pulse generator 28 (see Fig. 3B).
Inserting the lead 12 percutaneously allows the lead
12 to be placed quickly and easily, and placing the lead
12 in a peripheral location, i.e., muscle, where it is
less likely to be dislodged, addresses the lead migration
problems of spinal cord stimulation systems that result
in decreased pain relief, and the need for frequent
patient visits for reprogramming, and even lead
repositioning.
In an exemplary embodiment of the present invention,
placing the percutaneous IM lead 12 in muscle near the
motor point minimizes complications related to lead
placement and movement.
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In the percutaneous system 10, the IM lead 12, such
as a coiled fine wire IM lead may be used because it is
minimally-invasive and previous studies suggest it will
perform well in this location, i.e., in muscle, during
use.
In the fully implanted system 11, the same or
different lead 12 may be used, such as a slightly larger
IM lead that may be sized and configured to withstand
greater mechanical forces and resist migration during
long-term use. A larger IM lead 12 may be sized and
configured to withstand forces in excess of those
anticipated in flexible regions of the body, such as the
shoulder, elbow, neck, and knee.
II. Representative Indication for Temporary or
Chronic Reduction of Pain
Localized pain in any area of the body can be
treated with the percutaneous system 10 and/or the
implanted system 11 by applying electrical stimulation
using an IM lead directly to the effected area, e.g.,
motor point(s) within the muscle(s). The systems and
methods may work by interfering with or blocking pain
signals from reaching the brain.
An exemplary embodiment involves the treatment of
post-stroke shoulder pain. The treatment of post-stroke
shoulder pain with the percutaneous system 10 and/or the
implanted system 11 may only provide temporary pain
relief (as compared to permanent pain relief) once the
therapy is completed. This is based on data summarized in
a post-hoc analysis of the percutaneous electrical
stimulation pilot study data (Chae, et al., 2007), which
revealed that the most significant predictor of permanent
pain relief was time since stroke onset. For patients
treated less than 18 months after a stroke, pain was
reduced significantly during electrical stimulation
therapy and was maintained after the therapy was
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completed. However, for patients treated later than 18
months after a stroke, pain was reduced during electrical
stimulation therapy but returned after the therapy was
completed. Based on these data, a two product solution to
treat post-stroke shoulder pain may be benefitial. The
percutaneous system 10 may provide a temporary treatment
for all patients. If the pain returns, patients could
either choose to receive the temporary therapy again or
receive a permanent therapy such as a fully implantable
electrical stimulation system, which would be available
for permanent treatment of post-stroke shoulder pain.
If the temporary therapy significantly reduces the
shoulder pain, and the pain reduction is maintained after
the therapy is discontinued, then the treatment is
concluded. If the shoulder pain re-appears, either the
percutaneous system 10 may be used again for temporary
therapy or the chronic therapy system 11 can be
implanted.
In the post-stroke shoulder pain example, the
percutaneous system 10 stimulates the motor points of the
middle and posterior deltoid muscles for the therapeutic
treatment of shoulder pain by sending mild electrical
pulses through one or more IM leads 12 placed near the
motor points of these muscles (see Figs. 2 and 3A). The
mild electrical pulses from the percutaneous system 10
=
may also stimulate the axillary nerve, which innervates
these muscles, thereby achieving the same therapeutic
treatment of shoulder pain.
As previously described, percutaneous,
intramuscular, electrical stimulation is less painful and
better tolerated then surface electrical stimulation [Yu,
et al., 2001b]. It is critical to the success of the
therapy and overall patient compliance to be able to
deliver the stimulation therapy in a comfortable and
tolerable way.
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Percutaneous, intramuscular electrical stimulation
can be delivered at a lower stimulation frequency, which
is associated with reduced muscle fatigue. Higher
stimulation frequencies are used with surface electrical
stimulation systems to minimize stimulation-induced pain.
It is important to minimize the potential for muscle
fatigue in post-stroke patients, so that they can still
participate in the rehabilitation therapies for motor
recovery.
The percutaneous system 10 may be intended to be
used as a temporary stimulation therapy for post-stroke
shoulder pain. One or more intramuscular leads 12 having
electrodes 14 may be placed percutaneously in the
shoulder via an insulated introducer needle 30. In one
embodiment, one lead 12 may be placed near a middle
position between the motor point of the Middle Deltoid,
and the motor point of the Posterior Deltoid. In another
embodiment, one lead 12 may be placed near the motor
point of the Middle Deltoid, and another lead 12 may be
placed near the motor point of the Posterior Deltoid.
The percutaneous insertion site for one or both leads may
be slightly inferior of the glenohumeral joint. One or
both leads may be connected to the percutaneous system 10
which may be carried or placed (e.g., with adhesive or a
strap) on the anterior portion of the upper arm.
This position of the percutaneous system 10 allows
users and caregivers to operate the buttons 38 and see
the display 40 during use. A surface electrode 24, or
other known electrode types, may be connected to the
stimulator and serve as the return electrode (anode).
This surface electrode 24 may be placed adjacent to the
stimulator. Its position is not critical to the therapy
and it can be moved throughout the therapy to reduce the
risk of skin irritation. The case of the implantable
pulse generator 28 may serve as the return electrode in
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the fully implanted system 11.
III. Placing the IM Lead
Representative IM lead insertion techniques will now
be described to place one or more IM lead(s) 12 in a
desired location in muscle near the target motor
point(s). It is this lead placement that makes possible
the stimulation of the motor point(s) with one or more
lead(s) 12 to provide pain relief.
Instructions for use 58 can direct use of systems
and methods for the placement of an IM lead 12 in muscle
near the motor point for improved recruitment of target
nerves, e.g., with the placement of one or more leads 12.
The instructions for use may include instructions for
placing a lead 12 for the therapeutic electrical
stimulation of the motor point in a system for the relief
of pain, for example.
- The instructions for use may also include
instructions for recording stimulus parameters, including
intensity associated with a first sensation of
stimulation, a first noticeable muscle contraction, and a
maximum tolerable contraction at one or more locations,
which can be used to aid in determining desired
stimulation parameters for optimal stimulation, for
example, as will be described below.
To determine the optimal placement for the IM lead
12, test stimulation may be delivered through needle
electrodes and muscle responses may be observed. The
motor point(s) of the target muscle(s) may be located
first in order to confirm that the muscles are
innervated. Needle electrodes may be used because they
can be easily repositioned until the optimal location to
deliver stimulation is determined.
At least one lead(s) is desirably placed in muscle
tissue near the muscle's motor point. Electrical
stimulation is then applied to the motor point to
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determine if the peripheral nerve stimulation can block
the sensation of pain in the area(s) of pain and/or
reduce pain. The pain may be perceived to be contained
within a specific part(s) of the body, e.g., the muscle
in which the lead is placed.
Electrical stimulation may be applied to any motor
point throughout the body, such as target motor points in
muscles including, but not limited to deltoid (e.g.,
posterior, anterior, and/or middle) muscle, trapezius
muscle, erector spinae, gastrocnemius, occipitailis,
gluteus maximus, gluteus medius, iliotibial band, biceps
femoris, adductor magnus, semitendinosus, gracilis,
semimembranosus, sartorius, pectineus, adductor longus,
vastus medialis, vastus lateralis, and rectus femoris.
Electrical stimulation may be delivered through a
percutaneous and/or a fully =implantable system(s). To
determine if a person may benefit from stimulation, a
person may be tested in the clinical setting (e.g. an
office of a clinician, a laboratory, a procedure room, an
operating room, etc.) and/or sent home and/or tested
outside the clinical environment with external
stimulator(s) connected to temporary percutaneous and/or
= surface electrodes. The trial period may range from
minutes to hours to days to weeks to months, and in one
embodiment the trial period may be between 3 and 21 days.
Alternatively, it may be desirable to use a percutaneous
system(s) as a therapy without proceeding to a fully
implantable system. The duration of therapy for a
percutaneous system may range from minutes to days to
30= weeks to months to multiple years, and one embodiment
includes a duration ranging from 1 to 12 weeks.
Regulated current is the preferred type of
electrical stimulation, but other type(s) of stimulation
(e.g. non-regulated current such as voltage-regulated)
may also be used. Multiple types of intramuscular
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leads/electrodes may be used, including percutaneous
and/or implantable. Surface electrodes may be a standard
shape or they may be tailored if needed to fit the
contour of the skin.
In a preferred embodiment of a percutaneous system,
the surface electrode(s) may serve as the anode(s) (or
' return
electrode(s)), but the surface electrode(s) may be
used as the cathode(s) (active electrode(s)) if
necessary. When serving as a return electrode, the
location of the electrode is not critical and may be
positioned anywhere in the general vicinity, provided
that the current path does not cross the heart. If a
surface electrode serves as an active electrode, it
(they) may be positioned near the target stimulation
area(s), e.g., on the skin surface over the target motor
point.
The IM-lead may be placed near, but away from, the
motor point(s) of the target muscle(s) and may be
inserted via an introducer 30, which may be similar in
size and shape to a hypodermic needle. The introducer may
be any size. In one embodiment, the introducer may range
in size from 17g to 26g.
Prior to inserting the introducer 30, the insertion
site may be cleaned with a disinfectant (e.g., Betadine,
2% Chlorhexidine/80% alcohol, 10% povidone-iodine, or
similar agent). A local anesthetic(s) may be administered
topically and/or subcutaneously to the area in which the
lead and/or introducer(s) will be inserted.
The motor point(s) may be electrically stimulated
during and after placement of the lead- The lead may be
placed via multiple types of approaches. In one
embodiment, the approach(es) may be similar to a needle
placement for electromyography (EMG).
Though peripheral nerve stimulation may have a
success rate of over 80% and can almost completely
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eliminate pain in a majority of patients, the traditional
method of surgically placing the lead(s) is time
consuming and complex, which greatly limits its use
outside of academic institutions (Long 1973; Nashold and
Goldner 1975; Picaza et al. 1975; Nashold et al. 1982;
Gybels and Van Calenbergh 1990). Thus, a major limitation
of peripheral nerve stimulation is the lack of
appropriate electrode lead(s) and a method(s) to place
the electrode lead(s) near but away from peripheral
target nerve(s) quickly and easily and such that the
electrode(s) do not migrate (North 2003).
Methods for placing needle(s) for EMG may be adapted
so that they can be used to place an IM lead near a motor
point, with the lead inserted into muscle tissue such
that the lead is in electrical proximity to but not
touching the motor point. These improved methods will
greatly simplify the lead placement procedure(s), making
intramuscular motor point stimulation for the relief of
pain feasible economically and clinically.
Previously, the clinicians (e.g. pain specialists
and/or anesthesiologists) who typically see patients who
may benefit from peripheral nerve stimulation had neither
the time nor the training to perform the traditional
time-consuming lead-placement procedure, e.g., an open
surgery, previously required to place the lead(s) (e.g.,
cuff-type, spiral-type, and/or paddle-type leads) near
the peripheral target nerves innervating the region(s)-of
pain. The systems and methods of the present invention
adapt approaches for EMG so that they can be used to
place an IM lead that is adapted to resist migration in
muscle for the purpose stimulating a motor point for
providing pain relief in the muscle region(s) where the
lead is placed.
A. Instructions for Lead Placement
Figs. 5 through 10 show representative embodiments
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of the steps that representative instructions for use 58
can incorporate or direct for the percutaneous placement
of an IM lead 12 for the activation of a muscle A and
muscle B (e.g., the middle and posterior deltoid muscles)
in a system for the relief of pain, such as shoulder
pain. The instructions may include a series of steps that
can be followed to carry out portion or portions of the
procedure. It is to be appreciated that these series of
steps may be revised to place only one, or more than one
IM lead(s) to activate one motor point in one muscle, or
to activate two or more motor points in two or more
muscles (see Figs. 1A through 2).
In an exemplary embodiment, the steps may include,
but are not limited to:
1) Clean and prepare the area above the muscle(s) in
which the IM lead will be placed. For example, the
lateral aspect of the affected shoulder may first be
cleaned with Betadine, and a local subcutaneous
anesthetic (e.g., 2% lidocaine) may be administered.
2) Locate the motor points of two adjacent muscles
(Ti and B) and mark them, e.g., with an indelible marker.
For example, the motor points of the middle and posterior
heads of the deltoid muscle may be located using the
standard locations for clinical electromyography (Lee and
DeLisa, 2000).
3) Place a needle electrode (e.g., 24 G EMG needle
electrode) at the identified motor point locations for
muscle A and B. For example, needle electrode 20 is
placed at motor point A and needle electrode 22 is placed
at motor point B (see Fig. 6).
4) Place a surface stimulation return electrode 24
in proximity of the area where needle electrode 20 and 22
have been placed, which may also be in proximity of the
area in which the percutaneous lead 12 will be placed.
Test stimulation will be applied to each needle electrode
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20 and 22 inserted in muscle A and muscle B respectively,
with the surface electrode 24 providing a return path.
The surface electrode 24 may be placed adjacent to the
needle electrodes. Its position is not critical to the
therapy and it can be =moved throughout the therapy to
reduce the risk of skin irritation.
5) Couple pulse generator 26 to one needle electrode
and to the return electrode 24 (see Fig. 7). Set the
desired stimulation parameters. Test stimulation may be
delivered using a current-regulated pulse generator, for
example.
6) Deliver stimulation to each needle electrode
individually (i.e., one at a time) by slowly increasing
the stimulation intensity. Stimulation intensity is
defined here as the product of stimulation amplitude and
stimulation pulse duration. Increasing the stimulation
intensity can be achieved by keeping stimulation
amplitude constant and increasing stimulation pulse
duration, by keeping stimulation pulse duration constant
and increasing stimulation amplitude, or by increasing
both stimulation amplitude and stimulation pulse
duration. For example, the stimulation intensity may
initially be set at a very small, sub-sensation and sub-
motor threshold level. Then, the stimulation intensity
may be increased in small increments (e.g. 10 As) to
determine thresholds, for each motor point, at which the
first sensation of stimulation occurs (TsEN, stimulation
evokes the first visible muscle contraction (motor
threshold, Tmus), and stimulation evokes the maximum
tolerable muscle contraction (Tmx).
7) Each needle location may need to be adjusted to a
location that provides the strongest muscle contraction
at the lowest stimulation intensity for each muscle. If
the thresholds measured are determined to be high, it may
be an indicator that the electrode is placed too far away
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from the motor point. Placing the electrode closer to the
motor point, but not touching the motor point, may reduce
one or more thresholds, and the motor point may be found
when the threshold measurements are at a desired minimum.
For example, if Tmus is close to Twuc, the needle electrode
may be repositioned to lower the threshold such that Ts
Twoc, thus allowing for a strong contraction below the
maximum tolerable stimulus intensity.
8) Record the stimulation intensity at which the
first sensation, first noticeable muscle contraction, and
maximum tolerable muscle contraction occurs for both
muscle A and muscle B.
9) Determine the location at which both muscle A and
muscle B can be activated simultaneously using one
electrode, by placing a needle electrode 28 at the
approximate midpoint between the above identified
locations of needle electrodes 20, 22 for the motor
points of muscle A and muscle B respectively (see Fig.
8).
10) Deliver stimulation to the needle electrode 28
in an attempt to activate both muscle A and muscle B with
the one electrode. For example, deliver stimulation,
increasing stimulation intensity until both the middle
and posterior deltoids muscles (i.e., muscle A and muscle
B) are activated and are producing strong, visible, and
palpable muscle contraction at a tolerable stimulus
intensity.
11) If unable to achieve strong contraction of both
muscles A and B at a tolerable stimulus intensity, remove
the electrode 28 and place it a predetermined distance
(e.g., approximately 0.5 cm) closer to the muscle that
shows weaker contraction.
12) Repeat stimulation delivery and placement
location correction until both muscle A and muscle B
contract at the desired level at a tolerable stimulus
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intensity.
13) Mark this location with an indelible marker.
14) Record at which stimulation intensity first
sensation, first noticeable muscle contraction, and
maximum tolerable muscle contraction occurs.
At this point in the process, three parameters, Tsen,
Tmus, and Tmax have been measured for the three locations,
i.e., motor point of muscle A, motor point of muscle B,
and the optimal location between motor point of muscle A
and B to activate both muscles. It is expected that the
three parameters may be higher for the location in the
middle due to its larger relative distance to the motor
points at location A and B compared to both individual
locations A and B.
For the described one lead approach, the parameters
at location A and B may be used for guiding the
exploration of finding the ideal location between A and B
and the expected parameter range for the middle location.
The parameters at the middle location are then used to
program the parameters for the one lead placed in the
middle depending on the desired application. An
application might require sub-sensation stimulation, an
application might require sub-motor (but supra-sensation)
stimulation, an application might require supra-motor
threshold stimulation, and yet another application might
require stimulation at the maximum tolerable level. For
example, the pain relief application described may
require stimulation at Tmax in the middle location to
activate the posterior and middle deltoid fully at the
maximum tolerable stimulation intensity.
15) Remove all three needle electrodes 20, 22, and
28.
16) Identify the anticipated pathway of the
percutaneous lead 12. The entry point of the lead may be
a predetermined distance (e.g., approximately 2 to 3 cm)
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above the site identified as the location for the
placement between the muscles A and B, such that the lead
enters tangentially, for example. This placement may aid
in lead stability.
17) Administer a local anesthetic (e.g., 2%
lidocaine) at the skin surface and along the anticipated
pathway of the lead 12.
18) Insert the percutaneous lead 12 and electrode
14. For example, the lead may be placed percutaneously in
the muscle via an insulated 20 G introducer needle 30
(see Fig. 9).
19) Once the electrode 14 of the lead 12 has reached
the marked location (i.e., at or near the final position
of needle electrode 28), couple pulse generator 26 to the
lead 12 and to the return electrode 24, and deliver
stimulation to the lead 12 to verify proper placement.
Both muscle A and muscle B desirably contract. Desirably,
a strong, visible, and palpable contraction is evoked at
a stimulus intensity that is tolerable for the
participant.
Although not required, the position of the IM lead
may be checked by imaging techniques, such as ultrasound
or X-rays (fluoroscopy). Following placement of the
lead(s), the portion of the leads which exit the skin may
be secured to the skin using covering bandages and/or
adhesives.
20) The stimulation intensity =associated with first
sensation of stimulation (i.e., TsEN) , first noticeable
muscle contraction (i.e., Tmus) and maximum tolerable
contraction (i.e., TNAE), may again be recorded.
21) Turn off stimulation and secure the lead to the
skin.
22) Cover the percutaneous exit site 16 and lead 12
with a bandage 32. A bandage 34 may also be used to
secure the external portion of the lead 12 (or an
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extension cable used to couple the lead 12 to the
external pulse generator) to the skin (see Fig. 10). It
is anticipated that the length of time to identify the
optimal placement and place the IM lead to be less than
one hour.
It is possible that stimulation intensity may need
to be adjusted, i.e., increased or decreased slightly
during the treatment period due to causes such as
habituation or the subject becoming accustomed to
sensation, but the need for increased or decreased
intensity is unlikely and usually only occurs after
several days to weeks to months as the tissue
encapsulates and the subject accommodates to stimulation
(Nashold 1975; Krainick and Thoden 1981; Goldman et al.
2008). It is to be appreciated that the need for
increased intensity could happen at any time, even years
out, which would likely be due to either lead migration
or habituation, but may also be due reasons ranging from
nerve damage to plasticity/reorganization in the central
nervous system.
If stimulation is successful, i.e., if the screening
test and/or home-trial are successful, the patient's
percutaneous system 10 may be converted into a fully
implanted system 11 by replacing the external pulse
generator 26 with an implantable pulse generator 28 that
is implanted in a convenient area (e.g., in a
subcutaneous pocket over the hip or in the subclavicular
area).
In one embodiment, the IM lead 12 used in the
screening test and/or home-trial may be totally removed
and discarded, and a new completely implantable lead may
be tunneled subcutaneously and coupled to the implantable
pulse generator. In an alternative embodiment, a two part
lead may be incorporated in the screening test and/or
home-trial where the implantable part is completely under
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the skin and connected to a percutaneous connector (i.e.,
extension) that can be discarded after removal. The
implantable part may then be tunneled and coupled to the
implantable pulse generator, or a new sterile extension
may be used to couple the lead to the implantable pulse
generator, for example.
IV. Lead and Electrode Configurations
It is to be appreciated that the configuration of
one or more leads 12 and electrodes 14, and the manner in
which they are implanted can vary. Representative
embodiment(s) will be described, with reference to Figs.
11A through 12B.
Stimulation may be applied through an IM lead 12,
such as a fine wire intramuscular lead and electrode,
inserted via a needle introducer or surgically implanted
in proximity of the target site. Once proper placement is
confirmed, the needle may be withdrawn, leaving the lead
in place, i.e., in muscle in proximity to the motor
point. Stimulation may also be applied through a
penetrating electrode, such as an electrode array
comprised of any number (i.e., one or more) of needle-
like electrodes that are inserted into the target site.
Non-limiting examples of such micro electrode arrays
include Michigan or Utah arrays. In both cases, the lead
may placed using a needle-like introducer 30, allowing
the lead/electrode placement to be minimally invasive.
In one embodiment, the lead 12 may comprise a thin,
flexible component made of a metal and/or polymer
material. By "thin," it is contemplated that the lead
may not be greater than about 0.75 mm (0.030 inch) in
diameter, although it is to be appreciated that the lead
may have a larger or smaller diameter.
The lead 12 can comprise, e.g., one or more coiled
metal wires within an open or flexible elastomer core.
The wire can be insulated, e.g., with a biocompatible
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polymer film, such as polyfluorocarbon, polyimide, or
parylene. The lead is desirably coated with a textured,
bacteriostatic material, which helps to stabilize the
lead in a way that still permits easy removal at a later
date and increases tolerance.
The lead 12 may be electrically insulated everywhere
except at one (monopolar) (see Fig. 11A), or two
(bipolar), or four (quadpolar) (see Fig. 11B), or more,
for example, electrodes 14, i.e., conduction locations,
near the lead's distal tip. Each of the electrode(s) may
be connected to one or more conductors that run the
length of the lead 12, proving electrical continuity from
the electrode through the lead 12 to the stimulator 26 or
28.
The electrode(s) may comprise a de-insulated area of
an otherwise insulated conductor that runs the length of
an entirely insulated electrode. The de-insulated
conduction region of the conductor can be formed
differently, e.g., it can be wound with a different
pitch, or wound with a larger or smaller diameter, or
molded to a different dimension. The electrode may
comprise a separate material (e.g., metal or a conductive
polymer) exposed to the body tissue to which the
conductor of the wire is bonded.
The IM lead 12 is desirably provided in a sterile
package, and may be pre-loaded in the introducer needle
30. The lead 12 desirably possess mechanical properties
in terms of flexibility and fatigue life that provide an
operating life free of mechanical and/or electrical
failure, taking into account the= dynamics of the
surrounding muscle tissue (i.e., stretching, bending,
pushing, pulling, crushing, etc.). The material of the
electrode may discourage the in-growth of connective
tissue along its length, so as not to inhibit its
withdrawal at the end of its use. However, it may be
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desirable to encourage the in-growth of connective tissue
at the distal tip of the electrode, to enhance its
anchoring in tissue.
One embodiment of the lead 12 shown in Figs. 11A and
11B may comprise a minimally invasive coiled fine wire
lead 12 and electrode 14. The electrode 14 may also
include, at its distal tip, an anchoring element 48. In
the illustrated embodiment, the electrode 14 is the
anchoring element 48, which takes the form of a simple
barb or bend. The electrode may be bent to serve the
dual purpose of the anchoring barb and the stimulating
electrode. The anchoring element 48 may be sized and
configured so that, when in contact with tissue, it takes
purchase in tissue, to resist dislodgement or migration
of the electrode out of the correct location in the
surrounding tissue. Desirably, the anchoring element 48
is prevented from fully engaging body tissue until after
the electrode 14 has been deployed. The electrode may
not be deployed until after it has been correctly located
during the implantation (lead placement) process, as
previously described.
Alternative embodiments of an IM lead 12 shown in
Figs. 12A and 12B may also include at or near its distal
tip or region, one or more anchoring element(s) 70. In
the illustrated embodiment, the anchoring element 70
takes the form of an array of shovel-like paddles or
scallops or tabs 76 distal to the distal-most electrode
14, although a tab 76 or tabs could also be proximal to
the distal and/or proximal most electrode 14. The tabs 76
as shown are sized and configured so they will not cut or
score the surrounding tissue. The anchoring element 70is
sized and configured so that, when in contact with the
muscle tissue, it takes purchase in the muscle, to resist
dislodgement or migration of the electrode out of the
correct location in the surrounding muscle. In one
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embodiment, the anchoring element 70 may be prevented
from fully engaging body tissue until after the electrode
14 has been deployed. The electrode may not be deployed
until after it has been correctly located during the
implantation (lead placement) process, as previously
described. In addition, the lead 12 may include one or
more ink markings 74, 75 to aid the physician in a
predetermined placement.
Figs. 12A and 12B show the lead 12 may be
electrically insulated everywhere except at one
(monopolar) (See Fig. 12A), or two (bipolar), or four
(quadpolar) (see Fig. 12B), or more, for example,
electrodes 14, i.e., conduction locations, near the
lead's distal tip. Each of the
electrode(s) may be
connected to one or more conductors that run the length
of the lead 12, proving electrical continuity from the
electrode through the lead 12 to the stimulator 26 or 28.
Alternatively, or in combination, stimulation may be
applied through any type of nerve cuff (spiral, helical,
cylindrical, book, flat interface nerve electrode (FINE),
slowly closing FINE, etc.), paddle (or paddle-style)
electrode lead, cylindrical electrode lead, and/or other
lead that is surgically or percutaneously placed within
muscle at the target site.
In all cases, the lead may exit through the skin and
connect with one or more external stimulators 26, or the
lead(s) may be routed subcutaneously to one or more
implanted pulse generators 28, or they may be connected
as needed to internal and external coils for RF (Radio
Frequency) wireless telemetry communications or an
inductively coupled telemetry to control the implanted
pulse generator. The implanted pulse generator 28 may be
located some distance (remote) from the electrode 14, or
an implanted pulse generator may be integrated with an
electrode(s), eliminating the need to route the lead
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subcutaneously to the implanted pulse generator.
=In one embodiment, the lead 12 can include a metal
stylet within its core. Movement of the stylet with
respect to the body of the lead 12 and/or an associated
introducer 30 (if used) may be used to deploy the lead 12
by exposing the anchoring element 48, 70 to body tissue.
In this arrangement, the stylet is removed once the lead
12 is located in the desired region.
In another embodiment (see Figs. 13 through 15), the
lead 12 may be percutaneously implanted housed within
introducer 30 (i.e., a hypodermic needle). The introducer
30 comprises a shaft having sharpened needle-like distal
tip, which penetrates skin and tissue leading to the
targeted muscle region. The lead 12 is loaded (it may be
preloaded and provided in a kit) within a lumen in the
introducer 30, with the anchoring element 48, 70 shielded
from full tissue contact within the shaft of the
introducer 30 (see Fig. 13). In this way, the introducer
can be freely manipulated in tissue in search of a
desired final implantation site (see Fig. 14) before
deploying the lead 12 and withdrawing the introducer 30
(see Fig. 15).
The introducer 30 may be insulated along the length
of the shaft, except for those areas that correspond with
the exposed conduction surfaces of the electrode 14
housed inside the introducer 30. These surfaces on the
outside of the introducer 30 are electrically isolated
from each other and from the shaft of the introducer 30.
These surfaces may be electrically connected to a
connector 64 at the end of the introducer body (see Figs.
13 and 14). This allows connection to a stimulating
circuit 66 (see Fig. 13) during the implantation process.
The stimulating circuit 66 may comprise a stand alone
stimulator, or the external pulse generator 26 may be the
stimulating circuit. Applying stimulating current through
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the outside surfaces of the introducer 30 provides a
close approximation to the response that the electrode 14
will provide when it is deployed at the current location
of the introducer 30.
The introducer 30 may be sized and configured to be
bent by hand prior to its insertion through the skin.
This will allow the physician to place lead 12 in a
location that is not in an unobstructed straight line
with the insertion site. The construction and materials
of the introducer 30 allow bending without interfering
with the deployment of the lead 12 and withdrawal of the
introducer 30, leaving the lead 12 in the tissue.
V. Stimulation Parameters
Control of the stimulator and stimulation parameters
may be provided by one or more external controllers. In
the case of an external stimulator, the controller may be
integrated with the external stimulator. The implanted
pulse generator external controller (i.e., clinical
programmer) may be a remote unit that uses RF (Radio
Frequency) wireless telemetry communications (or an
inductively coupled telemetry) to control the implanted
pulse generator. The external or implantable pulse
generator may use passive charge recovery to generate the
stimulation waveform, regulated voltage (e.g., 10 mV to
20 V, or more or less), and/or regulated current (e.g.,
about 10 A to about 50 mA, or more or less). Passive
charge recovery is one method of generating a biphasic,
charge-balanced pulse as desired for tissue stimulation
without severe side effects due to a DC component of the
current.
A desired stimulation pulse may by cathodic
stimulation, although anodic will work, biphasic although
monophasic and/or multi-phasic will work, and
asymmetrical, although symmetrical will work. Its shape
may be rectangular or exponential or a combination of
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rectangular and exponential waveforms. The pulse width
of each phase may range between e.g., about 0.1 sec. to
about 1.0 sec., or more or less, as non-limiting
examples. See Fig. 16 for a representative stimulation
pulse.
Pulses may be applied in continuous or intermittent
trains (i.e., the stimulus frequency changes as a
function of time). In the case of intermittent pulses,
the on/off duty cycle of pulses may be symmetrical or
asymmetrical, and the duty cycle may be regular and
repeatable from one intermittent burst to the next or the
duty cycle of each set of bursts may vary in a random (or
pseudo random) fashion. Varying -the stimulus frequency
and/or duty cycle may assist in warding off habituation
because of the stimulus modulation.
The stimulating frequency may range from, e.g.,
about 1 Hz to about 300 Hz, or about 1 Hz to about 150
Hz, or about 1 Hz to about 50 Hz, or about 12 Hz to about
= 16 Hz, or more or less, and the frequency of stimulation
may be constant or varying. In the case of applying
stimulation with varying frequencies, the frequencies may
vary in a consistent and repeatable pattern or in a
random (or pseudo random) fashion or a combination of
repeatable and random patterns.
The stimulator intensity may range from, e.g.,
about 1.0 mA to about 2 mA, or about 0.1 mA to about 40
mA, or about 0.01 mA to about 200 mA, or more or less,
and about 100 sec to about 300 sec, or about 40 sec to
about 1000 gsec, or about 1 gsec to about 10,000 sec, or
= 30 more or less, sufficient to activate the target motor
point at some distance x1 mm away from the motor point.
If the stimulus intensity is too great, it may generate
muscle twitch(es) or contraction(s) sufficient to disrupt
correct placement of the lead. If stimulus intensity is
too low, the lead may be advanced too close to the motor
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point and possibly beyond the optimal position, possibly
leading incorrect guidance, nerve damage, mechanically
evoked sensation (e.g., pain and/or paresthesia) and/or
muscle contraction (i.e., when the lead touches the
nerve), inability to activate the target nerve fiber(s)
without activating non-target nerve fiber(s), improper
placement, and/or improper anchoring of the lead, e.g.,
the lead may be too close to the nerve and no longer able
to anchor appropriately in the muscle tissue.
The stimulator may be set to a frequency range from,
e.g., about 0.5 Hz to about 12 Hz, or about 0.1 Hz to
about 20 Hz, or about 0.05 Hz to about 40 Hz, or more or
less, and is desirably low enough to evoke visible muscle
twitches, i.e., non-fused muscle contraction, and/or
muscle contraction(s) of the target muscle(s) innervated
by the target nerve(s) but high enough that that the
target motor point will be activated before the lead is
advanced beyond the optimal position.
While stimulation is being applied, the lead (non-
limiting examples of the lead could include a single or
multi-contact electrode that is designed for temporary
(percutaneous) or long-term (implant) use or a needle
electrode (used for in-office testing only)) may be
advanced, e.g., slowly advanced, towards the target motor
point until the desired indicator response, e.g., muscle
twitch, muscle contraction, and/or some combination, is
obtained. The intensity may then be decreased, e.g.,
gradually decreased, as the lead is advanced closer to
the target motor point until the desired indicator
response(s) may be obtained at smaller intensity(ies)
within the target range, e.g., about 0.1 mA to about 1.0
mA, or about 0.09 mA to about 39 mA, or about 0.009 mA to
about 199 mA, or more or less, and about 100 sec to
about 300 sec, or about 40 sec to about 1000 sec, or
about 1 sec to about 10,000 sec, or more or less at
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some distance X2 mm, where X2 < X1, and (as a non-
limiting example) X1 may be multiple times larger than
X2, such as X1 2*X2, or X1 5*X2, or X1 20*X2, from
the target nerve. As a non-limiting example, if the
intensity is initially set to 1-1.5mA (at a lead-to-nerve
distance of X1), then it may be anticipated to get the
same response at an intensity of 0.3-0.5mA as the lead is
advanced to a distance of X2 from the nerve. This
assumes that the pulse width is left constant. It is to
be appreciated that the amplitude (mA) may be left
constant and decrease pulse width (us) as the lead is
advanced, but regardless, the effect of decreasing
stimulation intensity while advancing towards the nerve
is the same.
If a specific response(s), including a desired
response(s) and/or undesired response(s) can be obtained
at a range of intensities that are too low, then the lead
= may be located in a non-optimal location (e.g., too close
to the target motor point(s)). Non-limiting examples of
ranges of intensities that may be considered too low
include those that are a fraction, e.g., < 2/3, or < 1/5,
or < 1/10 of the intensities that obtained the desired
response(s) at the distance X1.
The preferred stimulus intensities are a function of
many variables, are meant to serve as non-limiting
examples only, and may need to be scaled accordingly. As
an example, if electrode shape, geometry, or surface area
were to change, then the stimulus intensities may need to
change appropriately. For example, if the intensities
were calculated for a lead with an electrode surface area
of approximately 20 mm2, then they may need to be sdaled
down accordingly to be used with a lead with an electrode
surface area of 0.2 mm2 because a decrease in stimulating
surface area may increase the current density, increasing
the potential to activate excitable tissue (e.g., target
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and non-target nerve (s) and/or fiber (s) ) . Alternatively,
if the intensities were calculated for a lead with an
electrode surface area of approximately 0.2 mm2, then the
intensities may need to be scaled up accordingly to be
used with a lead with an electrode surface area of 20
mm2. Alternatively, stimulus intensities may need to be
scaled to account for variations in electrode shape or
geometry (between or among electrodes) to compensate for
any resulting variations in current density. In a non-
limiting example, the electrode contact surface area may
be 0.1 mm2 to about 20 mm2, or 0.01 mm2 to about 40mm2, or
0.0001 mm2 to about 1000 mm2. In a non-limiting example,
the electrode contact configuration may include one or
more of the following characteristics: cylindrical,
conical, spherical, hemispherical, circular, triangular,
trapezoidal, raised (or elevated), depressed (or
recessed), flat, and/or borders and/or contours that are
continuous, intermittent (or interrupted), and/or
undulating.
Stimulus intensities may need to be scaled to
account for biological factors, including but not limited
to patient body size, weight, mass, habitus, age, and/or
neurological condition(s). As a non-limiting example,
patients that are older, have a higher body-mass index
(BMI), and/or neuropathy, e.g., due to diabetes, may need
to have stimulus intensities scaled higher (or lower)
accordingly (Bigeleisen et al. 2009). Bigeleisen et al.
indicated that a stimulation intensity of 0.2 mA and 100
sec indicates intraneural lead placement, i.e., the
lead/electrode is too close to the nerve because the lead
is inside the nerve. The lead
was a 22 gauge, 5cm
stimulating needle made by B. Braun, Bethlehem, PA. From
the above example, a calculation of the surface area of
the stimulating electrode would provide representative
data needed to scale stimulus intensities accordingly for
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larger or smaller contact areas.
As mentioned above, if the IM lead is too far away
from the target motor point(s), then stimulation may be
unable to evoke the desired response(s), e.g., muscle
contraction(s), and/or pain relief, in the desired
region(s) at the desired stimulus intensity(ies). If the
lead is too close to the target motor point(s), then
stimulation may be unable to evoke the same or similar
desired response(s) in the desired region(s) at the
desired stimulus intensity(ies) without evoking
undesirable response(s), such as unwanted and/or painful
muscle contraction(s), sensation(s), paresthesia(s),
increase in pain, and/or generation of additional pain in
related or unrelated area(s).
In some cases, it may be difficult to locate the
optimal IM lead placement or distance from the target
motor point(s) and/or it may be desirable to increase the
range of stimulus intensities that evoke the desired
response(s) without evoking the undesired response(s) so
alternative stimulus waveforms and/or combinations of
leads and/or electrode contacts may be used. A non-
limiting example of alternative stimulus waveforms may
include the use of a pre-pulse to increase the
excitability of the target fiber(s) and/or decrease the
excitability of the non-target fiber(s).
Those skilled in the art will recognize that, for
simplicity and clarity, the full structure and operation
of all systems and methods suitable for use with the
present invention is not being depicted or described
herein. Instead, only so much of an external and
implantable pulse generator and supporting hardware as is
unique to the present invention or necessary for an
understanding of the present invention is depicted and
described. The remainder of the construction and
operation of the pulse generators described herein may
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conform to any of the various current implementations and
practices known in the art.
VI. System Kits
As Figs. 17 and 18 show, the various devices and
components just described can be consolidated for use in
one or more functional kit(s) 60, 64, 68. The kits can
take various forms and the arrangement and contents of
the kits can vary. In the illustrated embodiments, each
kit 60, 64, 68 comprise a sterile, wrapped assembly. Each
kit 60, 64, 68 includes an interior tray 62 made, e.g.,
from die cut cardboard, plastic sheet, or thermo-formed
plastic material, which hold the contents. Kits 60, 64,
68 also desirably includes instructions for use 58 for
using the contents of the kit to carry out the procedures
described above, including the systems and methods
incorporating the percutaneous system 10 and/or the
implanted system 11.
The instructions 58 can, of course vary. The
instructions 58 may be physically present in the kits,
but can also be supplied separately. The instructions 58
can be embodied in separate instruction manuals, or in
video or audio tapes, CD's, and DVD's. The instructions
58 for use can also be available through an internet web
page.
The foregoing is considered as illustrative only of
the principles of the invention. Furthermore, since
numerous modifications and changes will readily occur to
those skilled in the art, it is not desired to limit the
invention to the exact construction and operation shown
and described. While the preferred embodiment has been
described, the details may be changed without departing
from the invention, which is defined by the claims.
