Note: Descriptions are shown in the official language in which they were submitted.
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IMPLANTABLE STIMULATOR SYSTEM AND METHOD
FOR TREATMENT OF URINARY IhICONT1NENCE
This application claims priority to, and the benefit of, prior United
States patent application Serial Number 601091,762, filed 06 July 1998, which
application is incorporated herein by reference.
Background of the Invention
The present invention relates to impiantable stimulator systems,
and more particularly to an implantable stimulator system utilizing one or
more
implantable microstimulators for treating urinary incontinence.
Urinary Incontinence is a clinical condition characterized by failure
to hold urine in the bladder under normal conditions of pressure and filling.
The
disorder can arise from either a failure of muscles around the bladder neck
and
urethra to maintain closure of the urinary outlet (so-called stress
incontinence)
or from abnormally heightened commands from the spinal cord to the bladder
that produce unanticipated bladder contractions (s~o- called urge
incontinence).
Many patients exhibit a grouping of symptoms suggesting that these disorders
may occur simultaneously in the same individual (so-called mixed
incontinence).
it is well known in the art that electric<~I stimulation in the region of
the pelvic floor can decrease the severity of incontinence. The improvement is
believed to be attained through at least three mechanisms: (1) by changing the
reflex thresholds of the bladder muscles responsible for bladder emptying, (2}
by strengthening the muscles that maintain closure on the bladder outlet, and
(3)
by changing the state of the neural pathways, musculature and/or bladder
beyond the period of stimulus application.
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The therapies currently available for incontinence have generally
been directed at improving muscle condition, as disclosed, e.g., in
applicant's
prior document W097118857 (PCT/US96/18680), published 29 May 1997.
Bladder hyper-reflexia and detrusor instability have proven more difficult to
treat.
However, evidence in the art suggests that it can be improved in many
individuals by stimulating peripheral nerves or nerve roots continuously or
intermittently to modulate transmission of excitatoryr nerve signals to the
bladder
muscles.
Several external and implantable approaches have been used to
stimulate the nerves supplying the bladder and pelvic region in orderto
decrease
the episodic incidences of unintentional bladder emptying. Those who
strengthen
periurethral muscles have usually employed 'vaginal or anal electrode
assemblages to stimulate muscle contractions repeatedly. These methods are
limited in their portability and are often poorly accepted by patients because
they
are inconvenient and often associated with unpleasant skin sensations.
Further,
the methods are inadequate for the treatment of urge incontinence in which
continual electrical stimulation is commonly needed to diminish or inhibit the
heightened reflexes of bladder muscles.
For the treatment of urge incontinence, surgically implanted
stimulators under battery or radio-frequency control have been described in
the
art. These stimulators have different forms, but acre usually comprised of an
implantable control rmodule to which is connected a series of leads that must
bo
routed to nerve bundles in eitherthe sacral roots emanating from the spinal
cord,
or the nerves supplying muscles, skin or other structures in the pelvic
region.
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The implantable devices are relatively large, expensive and challenging to
implant surgically. Thus, their use has generally bE;en confined to patients
with
severe symptoms and capacity to finance the surgery.
More recently, small implantable microstimulators have been
introduced that can be injected into soft tissues through a cannula or needle
See, e.g., U.S. Patent Numbers 5,324,316 and 5,405,367, both of which patents
are incorporated herein by reference. What is needed is a way to effectively
use
such small implantable microstimulators for the purpose of treating urinary
incontinence.
Summary of the Invention
The system and method taught in this invention includes the
injection or laparoscopic implantation of one or morE; battery- or radio-
frequency-
powered microstimulators beneath the skin of the perineum. The devices are
programmed using radio-frequency control via an external controllerthat can be
used by a physician to produce patterns of output stimulation pulses judged to
be efficacious by appropriate clinical testing to diminish incontinence
symptoms.
Such stimulation program is retained in the device or external controller and
is
transmitted when commanded to start and stop by a signal from the patient or
caregiver.
It is an object of this invention to reduce the incidence of
unintentional episodes of bladder emptying by stimulating nerve pathways that
diminish involuntary bladder contractions, improve closure of the bladder
outlet,
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andlor improve the long-term health of the urinary system by increasing
bladder
capacity and emptying.
It is a further object of this invention to teach a method whereby a
patient can receive one or more patterns of neural stimulation that can be
prescribed by a physician and administered without continuous oversight by a
clinical practitioner.
It is a feature of the invention to meet the above-identified objects
of the invention using a system of small implantable microstimulators of the
type
described in, or similar to those described in, thE; above-referenced patents
andlor patent applications.
Brief Description of the Drawings
The above and other aspects, features and advantages of the
present invention will be more apparent from the following more particular
description thereof, presented in conjunction with they following drawings
wherein:
FIG. 1 illustrates a programming system for use with an
implantable microstimulator; and
F1G. 2 shows an insertion system for use with an implantable
microstimulator.
Corresponding reference characters indicate corresponding
components throughout the severs! views of the drawings.
Detailed Description of the Invention
The following description is of i:he best mode presently
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contemplated for carrying out the invention. This description is not to be
taken
in a limiting sense, but is made merely for the purpn~se of describing the
general
principles of the invention. The scope of the invention should be determined
with reference to the claims.
Advantageously, the small size ofthe microstimulators referenced
above permits insertion of these devices beneath the skin of the perineum,
where they have the capability to stimulate the nerves and muscles in regions
surrounding the urethra and anus. For purposes o~f this patent application, it
is
sufficient to note that radio-frequency controlled rnicrostimulators receive
power
and control signals from an extra corporeal antenna coil via inductive
coupling
of a modulated radio-frequency field. Battery-operated microstimulators
incorporate a power source within the device itseli' but rely on radio-
frequency
controt to program stimulus sequences and to recharge the power source, when
needed, in accordance with the present invention, each implanted
microstimulator may be commanded to produce an electrical pulse of a
prescribed magnitude and duration and at a repetition rate sufficient to cause
stimulation of nerve axons.
The ability to implant small, less expensive microstimulators by
injection or laparoscopic insertion, rather than major surgery, significantly
reduces the expense and complication rates of implantable technologies for
urinary incontinence. For some patients, use of the stimulator for only a few
hours per day or week will improve the symptomatollogy of incontinence. In
such
patients, RF controlled devices provide an adequate amount of stimulation if
used intermittently for only a few hours per day to greatly decrease the
incidence
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of incontinent episodes. For many other patients, however, a continuous or
intermittent stimulation throughout the day is needed. These patients may best
utilize a stimulator that has a self-contained power source sufficient to
deliver
repeated pulses for several hours and that can be recharged repeatedly. In
accordance with the teachings of the present invention, the use of a
microstimulator with a rechargeable battery thus provides these patients the
portability needed to free the patient from reliance on radio-frequency power
delivery.
A battery-powered microstimulator suitable for use with the present
invention, and a control system for use with such battery-powered
microstimulator, is fully described in: W098137926, published 3 September
1998; W098/43700, published 8 October 1998; and W098/43701, published 8
October 1998; which publications are incorporatecl herein by reference.
Turning to FIG. 1, a preferred embodiment of the invention is
illustrated. As seen In FIG. 1, a rechargeable, battery-powered
microstimulator
10 is implanted into subcutaneous region 2, where current pulses delivered
from
its electrodes 14 and 16 stimulate nerve fibers 8. Nerve bundles in the
subcutaneous region may carry somatic sensory axons supplying receptors in
skin and muscle and somatic motor axons supplying skeletal muscle, as well as
autonomic axons supplying visceral and glandular structures and smooth
muscle.
When a sensory nerve is stimulated, it produces an electrical
impulse that is transmitted along the axon into the dorsal horn of the spinal
cord,
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where it can produce perceptible sensations, modulation of spinal cord
circuits
and reflex effects on motor pathways.
When a motor nerve is stimulatE:d, electrical impulses are
conveyed through its many peripheral branches that supply muscle fibers and
elicit contractions in them.
Electronic circuit 12, contained within the microstimulator 10,
dictates the amplitude and duration of the electrical current pulse, thereby
determining the number of nerve fibers excited by ~sach pulse. Electronic
circuit
12 receives operating power and (if a battery 15 is included within the
microstimulator) recharge power for battery 15 and data to be stored in memory
element 18 by inductive coupling from external controller 20 and its
associated
antenna coil 22.
During an initial programming se;>sion after implantation of
microstimulator 10, the prescribing physician uses a programming station 30 to
download a pattern of stimulus pulse delivery to controller 20, which saves
the
information in nonvolatile memory. Each time the microstimulators 10 are
recharged by controller 20, the stimulation parameters required from each
microstimulator 10 are transmitted via coil 22, along with the power required
for
recharging. The stimulation parameters are stored iin the memory element 18 of
each microstimuilator 10 as long as battery 15 has sufficient power to operate
the
microstimulator circuitry. Program delivery is initiated by start and stop
commands delivered by patient-governed control switch 2fi. In the preferred
embodiment, controller 20 is a hand-held module containing a microprocessor
and appropriate nonvolatile memory, such as electronically erasable
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programmable read-only-memory (EEPROM). Hiowever, it will be evident to
those of skill in electronic circuitry and computing that many different
system
architectures and components could be used to achieve similar functionality
with
either a battery-powered or radiofrequency-powered microstimulator device.
A preferred stimulation location for purposes of the present
invention is the pelvic floor. Direct stimulation of the pelvic floor nerves
bypasses the potential recruitment of other unrelatE:d nerve groups at the
sacral
roots. Other nerves in this region that may be targeted for stimulation
include
the pudendal nerve, pelvic nerve and the clitoral branches of the pudendal
nerve.
Stimulation parameters of pudendal nerve and sacral root
stimulation will generally fall in the following ranges:
Frequency: 2-20 pulses per second (pps).
Duration: 50-350 microseconds (ors).
Amplitude: 1-5 volts at about 1-50 milliarnps (mA).
It is to be understood that the above ranges are not absolute.
Rather, they provide a guide for the stimulation parameters to be used. One of
the attractive features provided by the invention is that the stimulation
parameters can be adjusted, as required, until an appropriate and efficacious
stimulation regime is achieved.
The microstimulators of the type described in the referenced
patents and patent publications represent a new class of generic implantable
stimulators. These devices are microminiature, single-channel stimulators that
can be injected through a 12 gauge needle, or similar device, in and around
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nerves and muscles. Under control of an RF coupled external transmitter,
microstimulators provide precise patterns of muscle activation with a variety
of
programmable pulse durations and intensities. While each microstimulator is a
single channel unit, the same external unit may control up to 256
microstimulators that then work in harmonious combination to create a
multichannel neuro-muscular control network. Because the microstimulators are
injectabie, they are minimally invasive, and may be injected in an outpatient
environment posing little clinical risk, and reducirng costs. If necessary,
such
microstimulators may be removed through a small surgical incision.
Advantageously, by implanting one or more microstimulators in the
manner described herein so as to selectively stimulate appropriate nerves
andlor
tissue, it is possible to create a system which: ('I) reduces the incidence of
unintentional episodes of bladder emptying by stimulating nerve pathways that
diminish involuntary bladder contractions, (2) improves closure of the bladder
outlet, andlor (3) improves the long-term health of the urinary system by
increasing bladder capacity and emptying.
In accordance with the present invention, a microstimulator is
injected into soft tissues by using an insertion device whose preferred
embodiment is shown in FIG 2. The hollow cannul<~ 110 of the insertion device
is comprised of a stiff dielectric material with sufficient lubricity to
permit the
undamaged passage of device 10 therethrough. Probe 120 is a rigid,
electrically
conductive trochar whose sharply pointed end extends beyond the end of the
tube. The trochar is used to deliver electrical impulses to the tissue at its
end.
Electrical stimuli can be delivered by means of the trochar 120 by connecting
an
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electrical stimulator (not shown) to connector 122 on the trochar. The initial
insertion site of the trochar, guided by a clinical knc>wledge of tissue
landmarks
or radiographic images, may be modified until stimulation produces excitation
of
nerves 8 judged by perceptible sensations or clinical demonstration of desired
effects on bladder or periurethrai muscle. Satisfactoiry stimulation of nerves
8 will
ensure that the end of the rod around the trochar is located in an appropriate
site
sufficiently close to nerves 8 so that electrical stimulation using the
microstimulator will also produce the desired nervE; excitation. Insertion of
the
microstimulator is accomplished by removing tro~char 120 and passing the
microstimulatorthrough the hollow cannula 110 using, e.g., a blunt-ended push-
rod 130.
It is thus seen that the invention provides a system which reduces
the incidence of unintentional episodes of bladder emptying by stimulating
nerve
pathways that diminish involuntary bladder contraci;ions, improve closure of
the
bladder outlet, and/or improve the long-term health of the urinary system by
increasing bladder capacity and emptying.
It is a further seen that the invention provides a method whereby
a patient can receive one or more patterns of neural stimulation that can be
prescribed by a physician and administered without continuous oversight by a
clinical practitioner.
Further, it is seen that the invention provides such a system and
method using small implantable microstimulators that may be implanted in the
desired tissue/nerve-stimulating locations by injection or laparoscopic
insertion
rather than major surgery.
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While the invention herein disclosed h;as been described by means
of specific embodiments and applications thereof, numerous modifications and
variations could be made thereto by those skilled in the art without departing
from the scope of the invention set forth in the claims.
