(12) United States Patent
`Whitehurst et al.
`
`USOO6871099B1
`(10) Patent No.:
`US 6,871,099 B1
`(45) Date of Patent:
`Mar. 22, 2005
`
`(54) FULLY IMPLANTABLE
`MICROSTIMULATOR FOR SPINAL CORD
`STIMULATION ASATHERAPY FOR
`CHRONIC PAIN
`
`(75) Inventors: Todd K. Whitehurst, Sherman Oaks,
`CA (US); James P. McGivern,
`Stevenson Ranch, CA (US); Carla M.
`Mann, Los Angeles, CA (US); Janusz
`A. Kuzma, Englewood, CO (US)
`(73) ASSignee: attany's Corporation,
`s
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 314 days.
`
`(*) Notice:
`
`(21) Appl. No.: 09/929,597
`(22) Filed:
`Aug. 13, 2001
`Related U.S. Application Data
`(60) Provisional application No. 60/226,333, filed on Aug. 18,
`2000.
`(51) Int. Cl. .................................................. A61N 1/18
`(52) U.S. Cl. ............................................ 607/46; 607/72
`(58) Field of Search .............................. 607/46, 40, 41,
`607/108, 58–62, 133, 116–118, 92, 148,
`2, 70, 72, 74; 128/898, 899; 600/29, 30,
`377; 604/20
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,646,940 A 3/1972 Timm et al.
`3. A : 2. E. S. '' 607/46
`2- - -
`oSugi et al.
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`
`FOREIGN PATENT DOCUMENTS
`wo. 5. K. S.
`WO-98/43700 A1 10/1998
`WO-98/43701 A1 10/1998
`WO-01/52729 A2
`7/2001
`
`wo
`WO
`WO
`WO
`
`OTHER PUBLICATIONS
`
`Cameron, et al., “Micromodular Implants to Provide Elec
`trical Stimulation of Paralyzed Muscles and Limbs”, IEEE
`Transactions on Biomedical Engineering, Vol. 44, No. 9,
`(Sep.1997), pp. 781-790.
`Shealy, et al., “Electrical Inhibition of Pain by Stimulation
`of the Dorsal col.'', Anesthesia and Analgesia, Vol. 46,
`(1967), pp. 489–491.
`
`(List continued on next page.)
`
`Primary Examiner Jeffrey R. Jastrzab
`(74) Attorney, Agent, or Firm-Laura Haburay Bishop;
`Bryant R. Gold
`(57)
`
`ABSTRACT
`
`An implantable stimulator(s), Small enough to be located
`near or within an area of the Spine responsible for Sensations
`in a region experiencing chronic pain uses a power Source/
`Storage device, Such as a rechargeable battery. Periodic
`recharging of Such a power Source/storage device is
`accomplished, for example, by inductive coupling with an
`external appliance. The Small Stimulator provides a means of
`Stimulating a nerve(s) or other tissue when desired, without
`the need for external appliances during the Stimulation
`Session. When necessary, external appliances are used for
`the transmission of data to and/or from the Stimulator(s) and
`for the transmission of power, it necessary. In a preferred
`embodiment, the System is capable of open- and closed-loop
`operation. In closed-loop operation, at least one implant
`includes at least one Sensor, and the Sensed condition is used
`to adjust Stimulation parameters.
`
`18 Claims, 8 Drawing Sheets
`
`
`
`24
`
`118
`
`LUMENIS EX1041
`Page 1
`
`

`

`US 6,871,099 B1
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`Delaporte, et al., “Lumbrosacral Spinal Fibrosis (Spinal
`Arachnoiditis): Its Diagnosis and Treatment by Spinal Cord
`Stimulation”, Spine, vol. 8, (1983), pp. 593–603.
`North, et al., “Spinal Cord Stimulation for Chronic, Intrac
`table Pain: Experience over Two Decades”, Neurosurgery,
`vol. 32, No. 3, (1993) pp. 384–395.
`Broseta, et al., “Chronic Epidural Dorsal Column Stimula
`tion in the Treatment of Causalgia Pain”, Appl Neuro
`physiol, vol. 45, (1982), pp. 190-194.
`Krainich, et al., “Pain Reduction in Amputees by Long Term
`Spinal Cord Stimulation (5 year study), J Neurosurg, vol.
`52, (1980) pp. 346–350.
`Jacobs, et al., “Epidural Spinal Cord Electrical Stimulation
`improves Microvascular Blood Flow in Severe Limb
`Ischemia', Annals of Surgery, vol. 207, No. 2, (1988), pp.
`179-182.
`Melzack, et al., “Pain Mechanisms: a New Theory”, Sci
`ence, vol. 150, (1965) pp. 971-979.
`Loeb, Richmond, Mann, Faltys, Whitehurst, and McGivern
`inventors for AB-047U1, U.S. Appl. No. 09/642,979; filed
`Aug 18, 2000; entitled “Implantable Stimulator System and
`Method for Treatment of Incontinence and Pain'.
`* cited by examiner
`
`5,312.439
`5,324,316
`5.330,515
`5,358,514
`5,405,367
`5,571,148
`5,702,428
`5,776,170
`5,824,021
`5,957.965
`5.984.854
`6,002.964
`6,018,682
`6,051,017
`6,058,331
`6,104,960
`6,161,044
`6,185,452
`6,208,894
`6,208.902
`6,240,316
`6,360,750
`6,464,687
`2001/0002441
`
`:
`
`5/1994
`6/1994
`7/1994
`10/1994
`4/1995
`11/1996
`12/1997
`7/1998
`10/1998
`9/1999
`11/1999
`12/1999
`1/2000
`4/2000
`5/2000
`8/2000
`12/2000
`2/2001
`3/2001
`3/2001
`5/2001
`3/2002
`10/2002
`5/2001
`
`Loeb
`Schulman et al.
`Rutecki et al.
`Schulman et al.
`Schulman et al.
`Loeb et al.
`Tippey et al.
`MacDonald et al.
`Rise ..................
`Moumane et al.
`Ishikawa et al.
`Feler et al. ........
`Rise ..................
`Loeb et al.
`King .................
`Duysens et al.
`Silverstone ........
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`Schulman et al.
`Boveja ..............
`Richmond et al.
`Gerber et al.
`Ishikawa et al.
`Boveja
`
`- - - - - - - - - - - 607/46
`
`- - - - - - - - - - 607/46
`
`- - - - - - - - - - 607/46
`
`- - - - - - - - - - - 607/46
`
`- - - - - - - - - - 607/45
`
`- - - - - - - - - - 607/62
`
`- - - - - - - - - - 607/45
`
`- - - - - - - - - - 607/46
`
`LUMENIS EX1041
`Page 2
`
`

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`U.S. Patent
`
`Mar. 22, 2005
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`U.S. Patent
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`Mar. 22, 2005
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`

`1
`FULLY MPLANTABLE
`MICROSTIMULATOR FOR SPINAL CORD
`STIMULATIONAS A THERAPY FOR
`CHRONIC PAN
`
`The present application claims the benefit of U.S. Pro
`visional Patent Application Ser. No. 60/226,333, filed Aug.
`18, 2000, which application is incorporated herein by ref
`erence in its entirety.
`
`FIELD OF THE INVENTION
`The present invention generally relates to implantable
`Stimulator Systems, and more particularly relates to an
`implantable Stimulator System utilizing one or more implant
`able microStimulators for treating chronic pain.
`
`BACKGROUND OF THE INVENTION
`Chronic pain is usually a multidimensional phenomenon
`involving complex physiological and emotional interac
`tions. For instance, one type of chronic pain, complex
`regional pain syndrome (CRPS) which includes the disor
`der formerly referred to as refleX Sympathetic dystrophy
`(RSD)-most often occurs after an injury, Such as a bone
`fracture. The pain is considered “complex regional” Since it
`is located in one region of the body (Such as an arm or leg),
`yet can spread to additional areas. Since CRPS typically
`affects the Sympathetic nervous System, which in turn affects
`all tissue levels (skin, bone, etc.), many Symptoms may
`occur. Pain is the main Symptom. Other Symptoms vary, but
`can include loSS of function, temperature changes, Swelling,
`Sensitivity to touch, and Skin changes.
`Another type of chronic pain, failed back Surgery Syn
`drome (FBSS), refers to patients who have undergone one or
`more Surgical procedures and continue to experience pain.
`Included in this condition are recurring disc herniation,
`epidural Scarring, and injured nerve roots.
`Arachnoiditis, a disease that occurs when the membrane
`in direct contact with the Spinal fluid becomes inflamed,
`causes chronic pain by pressing on the nerves. It is unclear
`what causes this condition.
`Yet another cause of chronic pain is inflammation and
`degeneration of peripheral nerves, called neuropathy. This
`condition is a common complication of diabetes, affecting
`60%–70% of diabetics. Pain in the lower limbs is a common
`Symptom.
`An estimated 10% of gynecological visits involve a
`complaint of chronic pelvic pain. In approximately one-third
`of patients with chronic pelvic pain, no identifiable cause is
`ever found, even with procedures as invasive as exploratory
`laparotomy. Such patients are treated Symptomatically for
`their pain.
`A multitude of other diseases and conditions cause
`chronic pain, including postherpetic neuralgia and fibromy
`algia Syndrome. Neurostimulation of Spinal nerves, nerve
`roots, and the Spinal cord has been demonstrated to provide
`Symptomatic treatment in patients with intractable chronic
`pain.
`Many other examples of chronic pain exist, as chronic
`pain may occur in any area of the body. For many Sufferers,
`no cause is ever found. Thus, many types of chronic pain are
`treated Symptomatically. For instance, many people Suffer
`from chronic headaches/migraine and/or facial pain. AS with
`other types of chronic pain, if the underlying cause is found,
`the cause may or may not be treatable. Alternatively, treat
`ment may be only to relieve the pain.
`
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`US 6,871,099 B1
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`All of the devices currently available for producing thera
`peutic Stimulation have drawbackS. Many are large devices
`that must apply Stimulation transcutaneously. For instance,
`transcutaneous electrical nerve stimulation (TENS) is used
`to modulate the Stimulus transmissions by which pain is felt
`by applying low-voltage electrical Stimulation to large
`peripheral nerve fibers via electrodes placed on the skin.
`TENS devices can produce significant discomfort and can
`only be used intermittently.
`Other devices require that a needle electrode(s) be
`inserted through the skin during Stimulation Sessions. These
`devices may only be used acutely, and may cause significant
`discomfort.
`Implantable, chronic Stimulation devices are available,
`but these currently require a significant Surgical procedure
`for implantation. Surgically implanted Stimulators, Such as
`Spinal cord Stimulators, have been described in the art. These
`Spinal cord Stimulators have different forms, but are usually
`comprised of an implantable control module to which is
`connected a Series of leads that must be routed to nerve
`bundles in the Spinal cord, to nerve roots and/or spinal
`nerves emanating from the Spinal cord, or to peripheral
`nerves. The implantable devices are relatively large and
`expensive. In addition, they require Significant Surgical
`procedures for placement of electrodes, leads, and process
`ing units. These devices may also require an external appa
`ratus that needs to be Strapped or otherwise affixed to the
`skin. Drawbacks, Such as size (of internal and/or external
`components), discomfort, inconvenience, complex Surgical
`procedures, and/or only acute or intermittent use has gen
`erally confined their use to patients with Severe Symptoms
`and the capacity to finance the Surgery.
`There are a number of theories regarding how Stimulation
`therapies Such as TENS machines and Spinal cord Stimula
`tors may inhibit or relieve pain. The most common theory
`gate theory orgate control theory-Suggests that Stimulation
`of fast conducting nerves that travel to the Spinal cord
`produces Signals that “beat' slower pain-carrying nerve
`Signals and, therefore, override/prevent the message of pain
`from reaching the Spinal cord. Thus, the Stimulation closes
`the “gate” of entry to the spinal cord. It is believed that small
`diameter nerve fibers carry the relatively slower-traveling
`pain Signals, while large diameter fibers carry Signals of e.g.,
`touch that travel more quickly to the brain.
`Spinal cord stimulation (also called dorsal column
`Stimulation) is best Suited for back and lower extremity pain
`related to adhesive arachnoiditis, FBSS, causalgia, phantom
`limb and Stump pain, and ischemic pain. Spinal cord Stimu
`lation is thought to relieve pain through the gate control
`theory described above. Thus, applying a direct physical or
`electrical Stimulus to the larger diameter nerve fibers of the
`Spinal cord should, in effect, block pain Signals from trav
`eling to the patient's brain. In 1967, Shealy and coworkers
`first utilized this concept, proposing to place Stimulating
`electrodes over the dorsal columns of the Spinal cord. (See
`Shealy C. N., Mortimer J. T., Reswick, J. B., “Electrical
`Inhibition of Pain by Stimulation of the Dorsal Column', in
`Anesthesia and Analgesia, 1967, Volume 46, pages
`489–491.) Since then, improvements in hardware and
`patient Selection have improved results with this procedure.
`The gate control theory has always been controversial, as
`there are certain conditions Such as hyperalgesia, which it
`does not fully explain. The relief of pain by electrical
`Stimulation of a peripheral nerve, or even of the Spinal cord,
`may be due to a frequency-related conduction block which
`acts on primary afferent branch points where dorsal column
`
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`US 6,871,099 B1
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`15
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`25
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`3
`fibers and dorsal horn collaterals diverge. Spinal cord Stimu
`lation patients tend to Show a preference for a minimum
`pulse repetition rate of 25 Hz.
`Stimulation may also involve direct inhibition of an
`abnormally firing or damaged nerve. A damaged nerve may
`be sensitive to slight mechanical stimuli (motion) and/or
`noradrenaline (a chemical utilized by the Sympathetic ner
`vous System), which in turn results in abnormal firing of the
`nerve’s pain fibers. It is theorized that stimulation relieves
`this pain by directly inhibiting the electrical firing occurring
`at the damaged nerve ends.
`Stimulation is also thought to control pain by triggering
`the release of endorphins. Endorphins are considered to be
`the body's own pain-killing chemicals. By binding to opioid
`receptors in the brain, endorphins have a potent analgesic
`effect.
`Recently, an alternative to 1) TENS, 2) percutaneous
`Stimulation, and 3) bulky implantable Stimulation assem
`blies has been introduced. Small, implantable microStimu
`lators have been introduced that can be injected into Soft
`tissues through a cannula or needle. What is needed is a way
`to effectively use Such Small, fully implantable, chronic
`neurostimulators for the purpose of treating chronic pain.
`BRIEF SUMMARY OF THE INVENTION
`The invention disclosed and claimed herein addresses the
`above and other needs and provides means and Systems for
`chronically stimulating a nerve root(s), spinal nerve?(s),
`and/or Spinal cord with a miniature implantable
`neurostimulator(s) that can be implanted via a minimal
`Surgical procedure.
`The nerve roots lie within the spinal column, and the
`Spinal nerves exit the Spinal column at the intervertebral
`foramen. To treat chronic pain, a miniature implantable
`electrical Stimulator, Such as a Stimulator Similar to a Bionic
`Neuron (also referred to as a BIONTM microstimulator) may
`be implanted via a minimal Surgical procedure (e.g., injec
`tion or Small incision) in the spinal column, preferably
`adjacent to a dorsal root, for stimulation of a nerve root(s),
`40
`and/or lateral to the intervertebral foramen for stimulation of
`a spinal nerve(s). Additionally or alternatively, a BION
`Stimulator may be implanted in or on the Spinal cord to
`Stimulate, e.g., the dorsal column or the Spinothalamic tract.
`A Single microStimulator may be implanted, or two or more
`microStimulators may be implanted to achieve greater Stimu
`lation of one or more nerve roots, Spinal nerves, and/or areas
`of the Spinal cord. For instance, one or more microStimulator
`(s) may be implanted adjacent to the dorsal root of the third
`and/or fourth lumbar nerve (i.e., L3 and/or L4), and/or
`lateral to the intervertebral foramen of the third and/or fourth
`lumbar nerve.
`Stimulation and control parameters of the implanted
`microStimulator are preferably adjusted to levels that are
`safe and efficacious with minimal patient discomfort. Dif
`ferent Stimulation parameters generally have different effects
`on neural tissue, and parameters are thus chosen to target
`Specific neural populations and to exclude others. For
`example, large diameter nerve fibers (e.g., A-C. and/or A-f
`fibers) respond to relatively lower current density stimula
`tion compared with Small diameter nerve fibers (e.g., A-6
`and/or C fibers).
`According to one embodiment of the invention, chronic
`pain may be treated with Stimulation to decrease excitement
`of targeted nerve roots, spinal nerves, and/or areas of the
`Spinal cord; high-frequency electrical Stimulation of Such
`nerve fiberS is likely to produce Such inhibition. According
`
`4
`to another embodiment of the invention, the Stimulation can
`increase excitement of targeted nerve roots, spinal nerves,
`and/or areas of the Spinal cord; low-frequency electrical
`Stimulation of Such nerve fiberS is likely to produce Such
`excitement.
`The neurostimulator also includes a means of Stimulating
`a nerve either intermittently or continuously. Specific Stimu
`lation parameters may provide therapeutic advantages for
`various forms of pain.
`The microstimulator used with the present invention
`preferably possesses one or more of the following proper
`ties:
`at least two electrodes for applying Stimulating current to
`Surrounding tissue;
`electronic and/or mechanical components encapsulated in
`a hermetic package made from biocompatible material
`(S);
`an electrical coil or other means of receiving energy
`and/or information inside the package, which receives
`power and/or data by inductive or radio-frequency (RF)
`coupling to a transmitting coil placed outside the body,
`thus avoiding the need for electrical leads to connect
`devices to a central implanted or external controller;
`means for receiving and/or transmitting Signals via telem
`etry;
`means for receiving and/or Storing electrical power within
`the microStimulator, and
`a form factor making the microStimulator implantable via
`a minimal Surgical procedure.
`A microstimulator may operate independently, or in a
`coordinated manner with other implanted devices, or with
`external devices. In addition, a microStimulator may incor
`porate means for Sensing pain, which it may then use to
`control Stimulation parameters in a closed loop manner.
`According to one embodiment of the invention, the Sensing
`and Stimulating means are incorporated into a Single micro
`Stimulator. According to another embodiment of the
`invention, a Sensing means communicates Sensed informa
`tion to at least one microStimulator with Stimulating means.
`Thus, the present invention provides a therapy for chronic
`pain that utilizes one or more miniature neurostimulators
`and is minimally invasive. The Simple implant procedure
`results in minimal Surgical time and possible error, with
`asSociated advantages over known treatments in terms of
`reduced expense and opportunity for infection or other
`complications. Other advantages, inter alia, of the present
`invention include the System's monitoring and programming
`capabilities, the power Source, Storage, and transfer
`mechanisms, the activation of the device by the patient or
`clinician, the System's open and closed-loop capabilities and
`closed-loop capabilities coupled with Sensing a need for
`and/or response to treatment, coordinated use of one or more
`Stimulators, and the Small size of the Stimulator.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The above and other aspects, features, and advantages of
`the present invention will be more apparent from the fol
`lowing more particular description thereof, presented in
`conjunction with the following drawings wherein:
`FIG. 1A illustrates the relation of spinal nerve roots to
`vertebrae;
`FIG. 1B illustrates the areas of skin innervated by the
`dorsal root axons at the various spinal levels,
`FIG. 2A depicts the nerve pathways in and near the
`thoracic part of the Spinal cord;
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`S
`FIG. 2B illustrates the principal fiber tracts of the spinal
`cord;
`FIG. 3 depicts a section through a lumbar vertebra;
`FIG. 4 illustrates an exemplary embodiment of a stimu
`lation System of the present invention;
`FIG. 5 illustrates preferred external components of the
`invention; and
`FIG. 6 depicts a system of implantable devices that
`communicate with each other and/or with external control/
`programming devices.
`Corresponding reference characters indicate correspond
`ing components throughout the Several views of the draw
`ings.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The following description is of the best mode presently
`contemplated for carrying out the invention. This descrip
`tion is not to be taken in a limiting Sense, but is made merely
`for the purpose of describing the general principles of the
`invention. The scope of the invention should be determined
`with reference to the claims.
`AS indicated above, the present invention is directed to
`treating chronic pain using one or more Small, implantable
`neurostimulators, referred to herein as “microStimulators'.
`The microStimulators of the present invention are preferably
`similar to the type referred to as BIONTM devices. The
`following documents describe various features and details
`asSociated with the manufacture, operation, and use of
`BION implantable microStimulators, and are all incorpo
`rated herein by reference:
`
`Application/Patent/
`Publication No.
`
`Filing/Publi
`cation Date
`
`Title
`
`U.S. Pat. No. 5,193,539 Issued
`Mar. 16, 1993
`U.S. Pat. No. 5,193,540 Issued
`Mar. 16, 1993
`
`U.S. Pat. No. 5,312,439 Issued
`May 17, 1994
`
`U.S. Pat. No. 5,324,316 Issued
`Jun. 28, 1994
`U.S. Pat. No. 5,405,367 Issued
`Apr. 11, 1995
`
`PCT Publication
`WO 98/37926
`PCT Publication
`WO 98,437OO
`
`PCT Publication
`WO 98,437O1
`
`published
`Sep. 3, 1998
`published
`Oct. 8, 1998
`
`published
`Oct. 8, 1998
`
`U.S. Pat. No. 6,051,017 Issued
`(application Ser. No.
`Apr. 18, 2000
`09/077,662)
`
`Implantable
`Microstimulator
`Structure and Method of
`Manufacture of an
`Implantable
`Microstimulator
`Implantable Device Having
`an Electrolytic Storage
`Electrode
`Implantable
`Microstimulator
`Structure and Method of
`Manufacture of an
`Implantable
`Microstimulator
`Battery-Powered Patient
`Implantable Device
`System of Implantable
`Devices For Monitoring
`and/or Affecting Body
`Parameters
`System of Implantable
`Devices For Monitoring
`and/or Affecting Body
`Parameters
`Improved Implantable
`Microstimulator and
`Systems Employing Same
`Micromodular Implants to
`published
`September 1997 Provide Electrical
`Stimulation of Paralyzed
`Muscles and Limbs, by
`Cameron, et al., published
`in IEEE Transactions on
`Biomedical Engineering,
`
`US 6,871,099 B1
`
`6
`
`-continued
`
`Application/Patent/
`Publication No.
`
`Filing/Publi
`cation Date
`
`Title
`
`Vol. 44, No. 9,
`pages 781-790.
`
`FIG. 1A illustrates the relation of spinal nerve roots to
`vertebrae, and FIG. 1B depicts the areas of skin innervated
`by the dorsal root axons at the various Spinal levels, known
`as dermatomes. FIG. 2A illustrates the nerve pathways in
`and near the thoracic portion of the spinal cord, while FIG.
`2B illustrates the principal fiber tracts of the spinal cord.
`FIG. 3 depicts a section through a lumbar vertebrae.
`Among the most common complaints of chronic pain is
`pain in the limbs. As depicted in FIGS. 1A and 1B, the
`nerves in and near the Spinal column from Vertebra L1 down
`to the top portion of the Sacrum (i.e., nerves L1, L2, L3, L4,
`L5, S1 and S2) have the greatest affect on sensations in the
`legs. Therefore, for example, in accordance with the teach
`ings of the present invention, electrical Stimulation at these
`same levels, L1-L5, S1, and S2, is provided to relieve leg
`pain.
`Under normal conditions, pain Signals are carried from
`the source of the pain through afferent nerve fibers which
`convey the impulses toward a nerve center (e.g., the brain or
`spinal cord). In the depictions of FIGS. 2A and 2B, the pain
`Signals are carried toward the Spinal cord via nerve fibers
`100. The pain Signals are then conducted up an ascending
`nerve pathway (via the spinothalamic tract 118 of the
`anterolateral System) to the brain, which processes the
`Signals and induces the pain Sensation. These pain signals
`travel through relatively Small diameter nerve fibers (i.e.,
`A-8 and C fibers) that enter the spinal cord at Lissauer's tract
`114, decussate at the Ventral commissure 116 over a distance
`of one to two Spinal Segments, then ascend to the brain
`within spinothalamic tract 118.
`To treat chronic pain, a microminiature stimulator 150,
`such as a BION microstimulator, illustrated, e.g., in FIGS.
`2A and 4, is preferably implanted e.g., adjacent to one or
`more dorsal (i.e., posterior) roots 110 and/or one or more
`spinal nerves 112. The nerve roots lie within the spinal
`column. The Spinal nerves exit the Spinal column at the
`intervertebral foramen 120 (FIG.3). As seen in FIG. 2A, the
`microStimulator is placed on or near a Spinal nerve 112,
`preferably lateral to intervertebral foramen 120, for stimu
`lation of a spinal nerve(s).
`Stimulating one or more dorsal nerve roots 110 and/or one
`or more spinal nerves 112, which would normally transmit
`pain Sensations, should cause the pain to be eliminated, or
`moderated. Additionally or alternatively, Stimulation of pain
`pathways in the Spinal cord, Such as along Lissauer's tract
`114, the ventral commissure 116, and/or the spinothalamic
`tract 118 may be used to treat chronic pain.
`Based on the gate control theory described earlier, Stimu
`lating fast-conducting, larger diameter nerve fibers will
`block, or gate, the Slower pain Signals from reaching the
`brain. The Somatic Sensory fibers responsible for touch,
`preSSure, and position Sense are carried through relatively
`large diameter nerve fibers (i.e., A-C. and/or A-f fibers) that
`enter the spinal cord and travel via a dorsal column 120,
`which is made up of the cuneate fasciculus 122 and the
`gracile fasciculus 124. AS Such, Stimulation may additionally
`or alternatively be applied to these fibers as a treatment for
`chronic pain.
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`LUMENIS EX1041
`Page 13
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`US 6,871,099 B1
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`In accordance with the present invention, a single micro
`stimulator 150 may be implanted, or two or more micro
`Stimulators may be implanted to achieve greater Stimulation
`of the targeted tissue, or for a longer period of time. AS
`shown in FIG. 4, microstimulator device 150 includes a
`narrow, elongated capsule 152 containing electronic cir
`cuitry 154 connected to electrodes 156 and 158, which pass
`through the walls of the capsule at either end. AS detailed in
`the referenced patent publications, electrodes 156 and 158
`comprise a stimulating electrode (to be placed close to the
`nerve) and an indifferent electrode (for completing the
`circuit). Other preferred configurations of microStimulator
`device 150 are possible, as is evident from the above
`referenced patent publications.
`Advantageously, a preferred implantable microStimulator
`150 is sufficiently small to permit its placement near the
`Structures to be stimulated. (AS used herein, “adjacent” and
`“near” mean as close as reasonably possible to targeted
`tissue, including touching or even being positioned within
`the tissue, but in general, may be as far as about 150 mm
`from the target tissue.) Capsule 152 preferably has a diam
`eter no greater than about 4-5 mm, more preferably only
`about 3 mm, and most preferably less than about 3 mm.
`Capsule length is preferably no greater than about 25-35
`mm, more preferably only about 20–25 mm, and most
`preferably less than about 20 mm. The shape of the micro
`stimulator is preferably determined by the structure of the
`desired target, the Surrounding area, and the method of
`insertion. A thin, elongated cylinder with electrodes at the
`ends, as shown in FIG. 4, is currently preferred, but other
`shapes, Such as Spheres, disks, or helical Structures, are
`possible.
`Microstimulator 150 is preferably implanted with a Sur
`gical insertion tool Specially designed for the purpose, or is
`injected (e.g., via a hypodermic needle). Alternatively,
`device 150 may be implanted via conventional Surgical
`methods, or may be inserted using other endoscopic or
`laparoscopic techniques. A more complicated Surgical pro
`cedure may be required for purposes of fixing the micro
`Stimulator in place.
`The external Surfaces of stimulator 150 are advanta
`geously composed of biocompatible materials. Capsule 152
`is preferably made of glass, ceramic, or other material that
`provides a hermetic package that will exclude water vapor
`but permit passage of electromagnetic fields used to transmit
`data and/or power. Electrodes 156 and 158 are preferably
`made of a noble or refractory metal or compound, Such as
`platinum, iridium, tantalum, titanium, titanium nitride,
`niobium, or alloys of any of these, in order to avoid
`corrosion or electrolysis which could damage the Surround
`ing tissues and the device.
`In one preferred embodiment of the instant invention,
`microstimulator 150 comprises two, leadless electrodes.
`However, either or both electrodes 156 and 158 may be
`located at the ends of short, flexible leads as described in
`U.S. patent application Ser. No. 09/624,130, filed Jul. 24,
`2000 (which claims priority to U.S. Provisional Patent
`Application No. 60/156,980, filed Oct. 1, 1999), which is
`incorporated herein by reference in its entirety. Other con
`figurations may also permit electrical Stimulation to be
`directed more locally to specific tissue a short distance from
`the Surgical fixation of the bulk of the implantable stimulator
`150, while allowing elements of stimulator 150 to be located
`in a more Surgically convenient Site. Such configurations
`minimize the distance traversed and the Surgical planes
`crossed by the device and any lead(s), which herein defines
`any means to locally direct the electrical Stimulation. In a
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`preferred embodiment, the leads (i.e., directing means) are
`no longer than about 150 mm.
`Microstimulator 150 preferably contains electronic cir
`cuitry 154 for receiving data and/or power from outside the
`body by inductive, radio-frequency (RF), or other electro
`magnetic coupling. In a preferred embodiment, electronic
`circuitry 154 includes an inductive coil for receiving and
`transmitting RF data and/or power, an integrated circuit (IC)
`chip for decoding and Storing Stimulation parameters and
`generating Stimulation pulses (either intermittent or
`continuous), and additional discrete electronic components
`required to complete the electronic circuit functions, e.g.
`capacitor(s), resistor(s), coil(s), and the like.
`In some preferred embodiments, microstimulator 150
`advantageously includes a programmable memory 160 for
`Storing a set(s) of Stimulation and control parameters, if
`required. This feature allows stimulation and control param
`eters to be adjusted to Settings that are Safe and efficacious
`with minimal discomfort for each individual. Specific
`parameters may provide therapeutic advantages for various
`forms and Severity of pain. For instance, Some patients may
`respond favorably to intermittent stimulation, while others
`may require continuous Stimulation to alleviate their pain.
`In addition, Stimulation parameters are typically chosen to
`target specific neural populations and to exclude others. For
`example, relatively low frequency neurostimulation (i.e.,
`less than about 100-150 Hz) may have an excitatory effect
`on Surrounding neural tissue, whereas relatively high fre
`quency neurostimulation (i.e., greater than about 100–150
`Hz) may have an inhibitory effect. In addition, large diam
`eter fibers (e.g., A-C. and/or A-f fibers) respond to relatively
`lower current density Stimulation compared with Small
`diameter fibers (e.g., A-6 and/or C fibers).
`The preferred implantable stimulator 150 also includes a
`power Source and/or power Storage device 162. Possible
`power options, described in more detail below, include but
`are not limited to an external power Source coupled to
`stimulator 150 via an RF link, a self-contained power so