US20110257660A1 - Apparatus for implanting an electrical stimulation lead - Google Patents

Abstract

In one embodiment, an introducer is provided for implanting an electrical stimulation lead to enable electrical stimulation of nerve tissue. The introducer includes an outer sheath and an inner penetrator. The outer sheath may accommodate insertion of the electrical stimulation lead and may be inserted into a human body near the nerve tissue. The inner penetrator is removably housed within the outer sheath and includes an inner channel configured to accommodate a guide wire, a tip end having a shape and size substantially conforming to that of the guide wire, a body region having a shape and size substantially conforming to that of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. At least a portion of the transition regions of the inner penetrator may flex to substantially follow flexures in the guide wire during advancement of the inner penetrator.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. application Ser. No. 12/098,007, filed Apr. 4, 2008, pending, which is a divisional of U.S. application Ser. No. 11/119,438, filed Apr. 29, 2005, now U.S. Pat. No. 7,359,755, which is a continuation-in-part of U.S. application Ser. No. 10/637,342, filed Aug. 8, 2003, now abandoned, the disclosures of which are fully incorporated herein by reference.
BACKGROUND
• This invention relates generally to electrical stimulation leads for medical applications and in particular to a method and apparatus for implanting an electrical stimulation lead using a flexible introducer One method of delivering electrical energy is to implant an electrode and position it in a precise location adjacent the spinal cord such that stimulation of the electrode causes a subjective sensation of numbness or tingling in the affected region of the body, known as “paresthesia.” Pain managing electrical energy is commonly delivered through electrodes positioned external to the dura layer surrounding the spinal cord. The electrodes may be carried by either of two primary vehicles: a percutaneous lead and a laminotomy or “paddle” lead.
• Percutaneous leads commonly have three or more equally-spaced electrodes. They are positioned above the dura layer using a needle that is passed through the skin, between the desired vertebrae and onto the top of the dura. Percutaneous leads deliver energy radially in all directions because of the circumferential nature of the electrode. Percutaneous leads can be implanted using a minimally invasive technique. In a typical percutaneous lead placement, a trial stimulation procedure is performed to determine the optimal location for the lead. Here, a needle is placed through the skin and between the desired vertebrae. The percutaneous lead is then threaded through the needle into the desired location over the spinal cord dura. Percutaneous leads may also be positioned in other regions of the body near peripheral nerves for the same purpose.
• Laminotomy or paddle style leads have a paddle-like configuration and typically possess multiple electrodes arranged in one or more independent columns. Paddle style leads provide a more focused energy delivery than percutaneous leads because electrodes may be present on only one surface of the lead. Paddle style leads may be desirable in certain situations because they provide more direct stimulation to a specific surface and require less energy to produce a desired effect. Because paddle style leads are larger than percutaneous leads, they have historically required surgical implantation through a procedure known as partial laminectomy that requires the resection and removal of vertebral tissue.
SUMMARY OF THE INVENTION
• The present invention provides an introducer and process for implanting a paddle style electrical stimulation lead.
• In one embodiment, an introducer is provided for implanting a paddle style electrical stimulation lead to enable electrical stimulation of nerve tissue. The introducer includes an outer sheath and an inner penetrator. The outer sheath may accommodate insertion of the paddle style electrical stimulation lead and may be inserted into a human body near the nerve tissue. The inner penetrator is removably housed within the outer sheath and includes an inner channel configured to accommodate a guide wire, a tip end having a shape and size substantially conforming to that of the guide wire, a body region having a shape and size substantially conforming to that of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. The inner penetrator may be advanced along the guide wire to a desired location relative to the nerve tissue and removed from the outer sheath leaving the outer sheath substantially in position for insertion of the paddle style electrical stimulation lead through the outer sheath into position proximate the nerve tissue. At least a portion of the transition regions of the inner penetrator may flex to substantially follow flexures in the guide wire during advancement of the inner penetrator along the guide wire.
• In another embodiment, a method is provided for implanting a paddle style electrical stimulation lead to enable electrical stimulation of nerve tissue. The method includes inserting a needle into tissue, positioning a guide wire through the needle into a desired location relative to the nerve tissue, removing the needle, and forming a tract for the paddle style electrical stimulation lead by advancing an introducer along the guide wire to a desired location. The introducer includes an outer sheath and inner penetrator removably housed within the outer sheath, the inner penetrator including a tip end having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the guide wire, a body region having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. At least a portion of the one or more transition regions flexes to substantially follow flexures in the guide wire during advancement of the inner penetrator along the guide wire. After advancing the introducer along the guide wire to the desired location, the inner penetrator is removed, leaving the outer sheath substantially in position, and the paddle style electrical stimulation lead is inserted through the outer sheath until the paddle style electrical stimulation lead is positioned proximate the nerve tissue.
• In another embodiment, a method is provided for implanting an electrical stimulation lead in a minimally invasive percutaneous manner to enable electrical stimulation of a human's spinal nerve tissue. The method includes inserting a needle into the human's epidural space and inserting a guide wire through the needle until an end of the guide wire is positioned in the epidural space at a desired location relative to the spinal nerve tissue to be stimulated. The position of the guide wire in the epidural space is verified using fluoroscopy, and the needle is removed, leaving the guide wire substantially in position. An introducer is advanced along the guide wire until an end of the inner penetrator of the introducer is positioned in the epidural space at a desired location with respect to the spinal nerve tissue to be stimulated. The introducer includes an outer sheath and an inner penetrator removably housed within the outer sheath, the inner penetrator of the introducer including an inner channel configured to accommodate the guide wire, a tip end having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the guide wire, a body region having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. as the inner penetrator of the introducer advances along the guide wire, at least one of the tip transition regions flexes to substantially follow flexures in the guide wire, and the outer sheath of the introducer forms a tract in the epidural space. The position of the introducer in the epidural space is verified using fluoroscopy. The guide wire and the inner penetrator of the introducer are removed, leaving the outer sheath of the introducer substantially in position. The electrical stimulation lead is inserted through the outer sheath of the introducer until the electrical stimulation lead is positioned in the epidural space proximate the spinal nerve tissue to be stimulated, and the positioning of the paddle style electrical stimulation lead in the epidural space is verified using fluoroscopy.
• In another embodiment, a system for implanting a paddle style electrical stimulation lead to enable electrical stimulation of a human's spinal nerve tissue is provided. The system includes a needle, a guide wire, and an introducer. The introducer includes an outer sheath and an inner penetrator. The outer sheath is configured to accommodate insertion of the paddle style electrical stimulation lead through the outer sheath and may be inserted through the human's skin and into the human's epidural space. The inner penetrator is removably housed within the outer sheath and includes an inner channel configured to accommodate a guide wire, a tip end having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the guide wire, a body region having a cross-sectional shape and size substantially conforming to a cross-sectional shape and size of the outer sheath, and one or more transition regions substantially connecting the tip end with the body region. The inner penetrator may be advanced along the guide wire until an end of the inner penetrator is positioned in the epidural space at a desired location relative to spinal nerve tissue to be stimulated, the outer sheath forming an insertion tract as the inner penetrator advances along the guide wire. A tip transition region of the inner penetrator is formed from a particular material and has a wall thickness sufficiently thin such that during advancement of the inner penetrator along the guide wire, the tip transition region may flex to substantially follow flexures in the guide wire. The inner penetrator is configured to be removed from the outer sheath leaving the outer sheath substantially in position for insertion of the paddle style electrical stimulation lead through the outer sheath into position proximate the spinal nerve tissue to be stimulated. The system also includes an implantable generator to power the paddle style electrical stimulation lead.
• In another embodiment, a lead introducer kit for preparing to implant an electrical stimulation lead for electrical stimulation of nerve tissue is provided. The lead introducer kit includes a needle, a guide wire, a lead blank having a similar shape and size as an electrical stimulation lead to be inserted proximate the nerve tissue, and an introducer. The lead blank is configured for insertion into the human body to determine whether the electrical stimulation lead may be inserted into position proximate nerve tissue to be stimulated. The introducer includes an outer sheath and an inner penetrator. The outer sheath is operable to be inserted into a human body near nerve tissue to be stimulated. The inner penetrator is removably housed within the outer sheath and includes an inner channel configured to accommodate the guide wire. The inner penetrator is configured to be advanced along the guide wire to a desired location relative to the nerve tissue and removed from the outer sheath leaving the outer sheath substantially in position for insertion of the lead blank through the outer sheath to determine whether the electrical stimulation lead may be inserted into position proximate the nerve tissue to be stimulated.
• In another embodiment, a method of removing an electrical stimulation lead from a human body is provided. A stimulation lead introducer is positioned over a body portion of an electrical stimulation lead that is at least partially implanted in a human body. The stimulation lead introducer includes an outer sheath and an inner penetrator removably housed within the outer sheath and comprising an inner channel, a tip region of the inner penetrator extending out from the outer sheath, the stimulation lead introducer being positioned such that the body portion of the electrical stimulation lead is partially disposed within an inner channel of the inner penetrator. The stimulation lead introducer is advanced along the body portion of the electrical stimulation lead until the tip region of the inner penetrator is located adjacent a stimulation portion of the electrical stimulation lead. The outer sheath is advanced relative to the inner penetrator until the outer sheath covers at least a portion of the stimulation portion of the electrical stimulation lead. The outer sheath, the inner penetrator, and the electrical stimulation lead are then removed from the human body.
• Particular embodiments of the present invention may provide one or more technical advantages. For example, certain embodiments may allow a paddle style electrical stimulation lead to be inserted using a minimally invasive procedure, using an introducer, rather than a partial laminectomy or other more invasive surgical procedure. Certain embodiments may provide a guide wire, introducer and paddle style electrical stimulation lead composed in part or entirely of radio-opaque material to allow for fluoroscopic verification of the position of the guide wire, introducer and lead. Certain embodiments may provide an inner penetrator including a hollow tip configured to extend beyond the outer sheath, the tip having a raised circumferential ridge configured to create resistance when the circumferential ridge contacts the human's tissue. Other embodiments may provide a smooth transition between the inner penetrator and the outer sheath to prevent the introducer from getting caught or stuck in the tissue. Certain embodiments may provide an inner penetrator having a substantially flexible tip that may flex to maneuver around obstructions or physical structures in the body and/or to follow curvatures in a guide wire. Certain embodiments may provide a lead introducer kit including a lead blank that may be used to determine whether an actual electrical stimulation lead may be inserted into a desired position in the body. Thus, in situations where it is determined (using the lead blank) that the actual lead cannot be inserted into the desired position in the body, the actual lead not need to be removed from its packaging or inserted into the body, thus saving the actual lead for another use. Certain embodiments may provide a desirable method for removing an implanted electrical stimulation lead using a lead introducer having an outer sheath and in inner penetrator. Certain embodiments may provide all, some, or none of these advantages. Certain embodiments may provide one or more other technical advantages, one or more of which may be readily apparent to those skilled in the art from the figures, description and claims included herein.
BRIEF DESCRIPTION OF THE DRAWINGS
• To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:
• FIG. 1A illustrates an example introducer for implanting a paddle style electrical stimulation lead according to one embodiment of the invention;
• FIG. 1B illustrates an example inner penetrator of the introducer shown inFIG. 1A;
• FIG. 1C illustrates an example of an outer sheath of the introducer shown inFIG. 1A;
• FIG. 1D illustrates an example of a tip of the introducer shown inFIG. 1A;
• FIG. 1E illustrates an example of a tip of the outer sheath of the introducer shown inFIG. 1A;
• FIG. 1F illustrates a side view of an example of the tip of the introducer shown inFIG. 1A;
• FIG. 2A illustrates an example introducer for implanting a paddle style electrical stimulation lead according to another embodiment of the invention;
• FIG. 2B illustrates an example inner penetrator of the introducer shown inFIG. 2A;
• FIG. 2C illustrates an example of an outer sheath of the introducer shown inFIG. 2A;
• FIG. 2D illustrates a perspective view of the introducer shown inFIG. 2A;
• FIG. 2E illustrates an example tip region of the inner penetrator shown inFIG. 2B;
• FIGS. 2F-2H illustrate an example of a body portion and tip portion of the outer sheath shown inFIG. 2C;
• FIG. 3A illustrates an example of a needle inserted into a human's epidural space;
• FIG. 3B illustrates an example of a guide wire being inserted through a needle into a human's epidural space;
• FIG. 3C illustrates an example of an introducer being inserted over a guide wire into a human's epidural space;
• FIG. 3D illustrates an example of an inner penetrator being removed from the outer sheath of an introducer in a human's epidural space;
• FIG. 3E illustrates an example of a paddle style lead being inserted through an introducer into a human's epidural space;
• FIG. 3F illustrates an example of a paddle style lead implanted in a human's epidural space;
• FIG. 4A illustrates an example of a stimulation system;
• FIG. 4B illustrates an example of a stimulation system; and
• FIG. 5 is a flow chart describing steps for implanting a stimulation system;
• FIGS. 6A-6E illustrate an example method of removing an implanted paddle style electrical stimulation lead from a human's epidural space using an introducer according to one embodiment of the invention;
• FIGS. 7A-7D illustrate example views of a lead introducer flexing as it moves along a guide wire within the body according to certain embodiments of the invention;
• FIG. 8 illustrates an example lead introducer kit for preparing to implant an electrical stimulation lead for electrical stimulation of nerve tissue in a human, according to one embodiment of the invention;
• FIG. 9 illustrates an example lead blank including a paddle style stimulating portion having a scalloped shape;
• FIG. 10 illustrates an example paddle style electrical stimulation lead having electrodes on only one side, and markings indicating the directional orientation of the lead, according to one embodiment of the invention;
• FIG. 11 illustrates an example paddle style electrical stimulation lead having a substantially uniform paddle-shaped cross-section extending along the body of the lead, according to one embodiment of the invention; and
• FIG. 12 illustrates an example paddle style electrical stimulation lead having a tear away body portion, according to one embodiment of the invention.
DESCRIPTION OF EXAMPLE EMBODIMENTS
• FIG. 1A illustrates anexample introducer10afor implanting a paddle style electrical stimulation lead percutaneously according to one embodiment of the invention.Introducer10amay be used to percutaneously introduce a percutaneous or paddle style lead into the epidural space of a user who requires electrical stimulation treatment directed to spinal nerve tissue, for example, for pain management. For example, and not by way of limitation, introducer10amay be used to percutaneously introduce any of the percutaneous or paddle style leads shown and/or described in U.S. Publication No. 2002/0022873, filed on Aug. 10, 2001; U.S. Provisional Application No. 60/645,405, filed on Apr. 28, 2004; and/or U.S. Provisional Application No. 60/566,373, filed on Jan. 19, 2005. The same or an analogous, perhaps smaller, introducer10amay be used to implant a percutaneous or paddle style lead into other tissue for electrostimulation treatment of a peripheral nerve. In one embodiment, introducer10aincludes anouter sheath12aand aninner penetrator14a.
• FIG. 1B illustrates an exampleinner penetrator14adisassembled fromouter sheath12a.Inner penetrator14aincludeshandle16a,connector17a,andbody18ahaving proximal end19aand distal end or tip20a.Tip20amay be tapered.Connector17aconnects handle16atobody18a.Aninner channel22ais formed throughhandle16aandbody18aand connects opening26aofhandle16ato opening21aoftip20a.Inner channel22amay be configured to attach to a syringe.Inner channel22ais wide enough to accommodate guide wires of various sizes along which introducer10amay be advanced during use.Channel22amay taper or otherwise decrease in diameter as it traversesconnector17aat the handle-body junction.Inner penetrator14amay be formed from a plastic, such as silastic, HDPE or another polymer, or any other suitable material.Tip20aofinner penetrator14amay be curved as shown inFIGS. 1A-1C or may be curved into any other suitable shapes by an operator before inserting the introducer. In certain embodiments,inner penetrator14amay be bent or curved into a suitable configuration to allow passage around an anatomical obstruction, or formed into any other shape suitable for particular anatomic regions of the body.
• FIG. 1C illustratesouter sheath12adisassembled frominner penetrator14a.The lumen28 ofouter sheath12amay range in width, for example from approximately 2 mm to approximately 6 mm. Lumen28 may be oblong, oval, or substantially rectangular as needed to accommodate paddle style leads of various configurations.Outer sheath12amay taper slightly at tip29. Tip29 ofouter sheath12amay be beveled to allow easier passage through tissue and to allowinner penetrator14ato protrude out of tip29.
• In some embodiments,outer sheath12amay be formed from a flexible material, such as a plastic or polymer, such as PEBAX, or any other suitable polyethylene type material, for example, such thatouter sheath12amay flex to follow a guide wire and/or to maneuver around obstructions or physical structures in the body. In other embodiments,outer sheath12amay be formed from a more rigid material, such as a metal, such as stainless steel or titanium, or any other suitable material that is stiff and resists bending whenouter sheath12ais inserted through the paravertebral tissue and into the epidural space. In one embodiment,inner penetrator14aincludes taperedtip20ashown inFIG. 1D.Tapered tip20aprotrudes out ofouter sheath12a.Tapered tip20apreferably allows introducer10ato pass easily over a guide wire without creating a false passage in an undesirable location in the tissue.
• In one embodiment ofouter sheath12a,shown inFIGS. 1D-1F, tip20aincludes a raised circumferential shoulder orridge23aconfigured to provide an indication or “feel” to a physician as raisedridge23acomes in contact with the ligamentum flavum. This “feel” occurs when raisedridge23acomes in contact with the ligamentum flavum causing a slight resistance, pressure, or “notch” feel to the physician as raisedridge23acomes in contact with and passes through the ligamentum flavum. As many physicians rely on “feel” while performing delicate procedures, this aspect may provide an important indication to the physician as to the location ofouter sheath12aand thus introducer10aas a whole.
• Such a raisedridge23acan also be applied to needles or cutting devices that otherwise fail to provide physicians sufficient “feel” or a locative indication as the needle cuts through the ligamentum flavum. For example, the edge ofouter sheath12ainFIG. 1E could be configured into a cutting surface for a paddle insertion type needle. The improvement of raisedridge23aon such a cutting device would provide the needed “feel” or indication to the physician as to where the needle was in the human tissue, thus providing confidence to the physician, as the physician uses such a large needle, that the needle has not yet entered the interthecal space.
• Further, raisedridge23aassists in spreading the fibers of the paravertebral muscle and ligaments as it is inserted. Raisedridge23amay be angled to assist insertion, for example, at an angle of thirty-five to forty-five degrees or any other angle that would facilitate passage of outer sheath through tissue. During insertion, raisedridge23aultimately makes contact with the ligamentum flavum and rests against it during insertion of a guide wire and an electrical stimulation lead.
• As shown inFIGS. 1D and 1E, in some embodiments,outer sheath12a,lumen28a,andinner penetrator14amay have oblong, oval, or substantially rectangular cross-sections as needed to accommodate paddle style leads of various configurations. Such configuration also preventsinner penetrator14afrom rotating withinlumen28aofouter sheath12a,which may be advantageous for inserting a lead into the target region in the body. For example, such configuration that prevents the rotation ofinner penetrator14awithinlumen28amay allow an operator to ensure that the lead is facing in the desired direction. In addition, a non-circular cross-section may provide additional flexibility tointroducer10, which may be advantageous for navigating into particular regions in the body, such as the epidural region, for example.
• In one embodiment,outer sheath12a,inner penetrator14a,or both may be formed from radio-opaque material or may include radio-opaque markers that allow the position ofouter sheath12a,inner penetrator14a,or both to be visualized with fluoroscopy or plain x-rays, for example, during the insertion process to insure proper positioning in the epidural space.
• FIG. 2A illustrates anotherexample introducer10bfor implanting a paddle style electrical stimulation lead percutaneously according to another embodiment of the invention.Introducer10bmay be used to percutaneously introduce a percutaneous or paddle style lead into the epidural space of a user who requires electrical stimulation treatment directed to nerve tissue (e.g., spinal nerve tissue), for example, for pain management. The same or an analogous, perhaps smaller,introducer10bmay be used to implant a percutaneous or paddle style lead into other tissue for electrostimulation treatment of a peripheral nerve. Likeintroducer10a,introducer10bmay include anouter sheath12band aninner penetrator14b.
• FIG. 2B illustrates an exampleinner penetrator14bdisassembled fromouter sheath12b.Inner penetrator14bincludes ahandle portion16b,abody portion18b,a distal or tip end20b,and atip portion25bconnectingbody portion18bwith atip end20b.Tip portion25bmay include one ormore transition regions26b,which may provide a transition between the cross-sectional shape and size ofbody portion18band the cross-sectional shape and size oftip end20b,as discussed in greater detail with reference toFIG. 2D. For example, one ormore transition regions26bmay be tapered.Handle portion16bmay include an innerpenetrator locking device32b,which may interact with a locking device ofouter sheath12b(discussed below regardingFIG. 2C) in order to lockinner penetrator14bin position withinouter sheath12b.However, any other type of handle known to those in the art may also be used.
• Aninner channel22bis formed throughhandle portion16b,body portion18b,andtip portion25bto connect anopening26binhandle portion16bwith anopening21bintip end20b.Inner channel22bmay be configured to attach to a syringe at a lure lock located athandle portion16bor through another opening.Inner channel22bmay be configured to accommodate guide wires of various sizes along which introducer10bmay be advanced during use. In this embodiment, the diameter ofinner channel22btapersproximate handle portion16b,remains constant along the length ofbody portion16b,and tapers slightlyproximate tip region25b.However, in other embodiments,inner channel22bmay not include a tapered portion.Inner penetrator14bmay be formed from a plastic, such as silastic, HDPE or another polymer, or any other suitable material. In addition, in some embodiments, the shape ofinner penetrator14bmay be configured to facilitate steering ofinner penetrator14b.For example, one or more indentions, notches, or score lines may be formed ininner penetrator14bto increase the flexibility and steerability ofinner penetrator14b.
• FIG. 2C illustratesouter sheath12bdisassembled frominner penetrator14b.Outer sheath12bincludes ahandle portion27b,abody portion31b,atip portion30b,and atip end29bthrough whichinner penetrator14bmay protrude, such as shown inFIGS. 2A and 2D. The inner channel, or lumen,28bofouter sheath12bmay range in width, for example from approximately 2 mm to approximately 6 mm. In some embodiments, the cross-section oflumen28bmay be oblong, oval, or substantially rectangular as needed to accommodate paddle style leads of various configurations. The outer surface ofouter sheath12bmay have a similar cross-section aslumen28b.Thus, for example, the outer surface ofouter sheath12bmay have an oblong, oval, or substantially rectangular cross-section. In some embodiments,outer sheath12b,lumen28b,andinner penetrator14bmay have oblong, oval, or substantially rectangular cross-sections as needed to accommodate paddle style leads of various configurations. As discussed above regardingintroducer10a,such configuration may preventinner penetrator14bfrom rotating withinlumen28bofouter sheath12b,which may be advantageous for inserting and/or navigating a lead into the target region in the body.Outer sheath12bmay taper slightlyproximate tip end29b,which may be beveled to be substantially flush against the outer surface ofinner penetrator14bto allow easier passage through tissue, as discussed below.
• In some embodiments,outer sheath12bis formed from a plastic or polymer material, or any other suitable material that allows flexing whenouter sheath12bis inserted through certain tissue, such as the paravertebral tissue and into the epidural space, for example. In a particular embodiment, bothouter sheath12bandinner penetrator14bare formed from plastic or polymer materials, butinner penetrator14bis more flexible thanouter sheath12bdue to the particular materials used to formouter sheath12bandinner penetrator14band/or the size, wall thickness, or other dimensions ofouter sheath12bandinner penetrator14b.In other embodiments,outer sheath12bis formed from substantially rigid material, such as a metal, such as stainless steel or titanium, or any other suitable material that is stiff and resists flexing whenouter sheath12bis inserted through the paravertebral tissue and into the epidural space.
• Handle portion27bmay include an outersheath locking device33b,which may interact with innerpenetrator locking device32bshown inFIG. 2B in order to lockinner penetrator14bin position withinouter sheath12b.Innerpenetrator locking device32band outersheath locking device33bmay include any devices suitable to interact to lockinner penetrator14bwithinouter sheath12b.For example, lockingdevices32band33bmay include threaded portions such thatinner penetrator14bandouter sheath12bmay be locked and unlocked by rotation of at least one of lockingdevices32band33b.As another example, lockingdevices32band33bmay snap together to lockinner penetrator14bwithinouter sheath12b.Lockinginner penetrator14bwithinouter sheath12bmay preventouter sheath12bfrom sliding down overinner penetrator14b,which may damage tissue in the body or cause other problems. However, some embodiments do not include a locking mechanism.
• In some embodiments,inner penetrator14band/orouter sheath12bmay be partially or completely formed from one or more materials that may be detected by one or more medical imaging techniques, such as ultrasound, fluoroscopy, MRI, fMRI and/or X-ray, such that the location of theinner penetrator14band/orouter sheath12bwithin the human body may be determined. For example,inner penetrator14band/orouter sheath12bmay be formed from or doped with a radio-opaque material, such as barium sulphate (BaSO₄), for example. As another example,inner penetrator14band/orouter sheath12bmay include markers that may be detected by one or more of such medical imaging techniques. As shown inFIGS. 2B and 2C,inner penetrator14bmay include a first radio-opaque marker34bandouter sheath12bmay include a second radio-opaque marker35b.The location ofinner penetrator14brelative toouter sheath12bmay be determined based on the determined relative location ofmarkers34band35b.In addition, first and second radio-opaque markers34band35bmay have different radiopacity such thatmarkers34band35bmay be distinguished from each other.
• FIG. 2D illustrates a perspective view ofintroducer10b.In this configuration,inner penetrator14bmay be locked withinouter sheath12bby lockingdevices32band33b.Tip portion25bofinner penetrator14bprotrudes throughtip end29bofouter sheath12b.As discussed below with reference toFIGS. 3A-3F,inner penetrator14bmay be configured to be advanced along a guide wire to a desired location relative to particular nerve tissue to be stimulated and removed fromouter sheath12b,leavingouter sheath12bsubstantially in position for insertion of an electrical stimulation lead throughouter sheath12binto position proximate the nerve tissue to be stimulated.Tip portion25bofinner penetrator14bmay be sufficient to flex to substantially follow flexures (such as bends or curves) in the guide wire during advancement ofinner penetrator14balong the guide wire. In order to provide such flexibility,tip portion25bmay be formed from particular flexible materials and may have sufficiently thin walls, as discussed below with reference toFIG. 2E. In addition, as discussed above,outer sheath12bmay be formed from flexible materials and may have sufficiently thin walls in order to provide some flexibility ofintroducer10b.
• FIG. 2E illustrates a partial detailed view ofbody portion18bandtip portion25bofinner penetrator14b,as well as a portion oftip portion30bofouter sheath12b,ofintroducer10b.In this embodiment,tip portion25bofinner penetrator14bincludes threetransition regions26b,which may provide a transition between the cross-sectional shape and size ofbody portion18band the cross-sectional shape and size oftip end20b.Transition regions26binclude atip transition region36b,amiddle transition region37b,and abody transition region38b.Tip transition region36bhas a substantially circular cross-section extending along the length oftip transition region36band tapering slightly towardtip end20b.Middle transition region37bhas a substantially circular and constant cross-section along the length ofmiddle transition region37b.Thus, in this embodiment,middle transition region37bis not tapered.Body transition region38bhas a cross-section that transitions from the cross-section ofbody portion18b,which may substantially match the cross-section oflumen28bofouter sheath12b.In a particular embodiment,body transition region38btransitions from a substantially oval cross-sectionadjacent body portion18bto a substantially circular cross-section adjacentmiddle transition region37b.Body transition region38bmay have a more severe taper thantip transition region36b.
• The materials and dimensions of one or more oftip transition region36b,middle transition region37b,andbody transition region38bmay be selected to provide substantial flexibility to tipregion25bsuch thatinner penetrator14bmay flex around particular features in the body, and such that when theinner penetrator14bis advanced along a guide wire,tip regions25bmay flex to substantially follow flexures in the guide wire such that the guide wire is not significantly displaced by the advancingtip region25bofinner penetrator14b.
• For example, the wall thickness oftip transition region36b,denoted as thickness “T_ipt,” may decrease towardtip end20b.In some embodiments, the wall thickness T_iptoftip transition region36bis less than or approximately equal to 0.02 inches at its thickest point alongtip transition region36b.The wall thickness T_iptoftip transition region36bmay be less than 0.01 inches attip end20b.In a particular embodiment, the wall thickness T_iptis approximately 0.006 inches attip end20b.The decreased wall thickness, T_ipt, oftip transition region36btowardtip end20bmay provide for increased flexibility oftip transition region36b.In addition, as shown inFIG. 2E, both the inner diameter, denoted as “ID_ipt,” and the outer diameter, denoted as “OD_ipt,” oftip transition region36bmay decrease or taper towardtip end20b.The tapered outer diameter OD_iptand reduced wall thickness, T_ipt, oftip transition region36battip end20bmay provide a relatively smooth transition between tip end20band a guide wire extending through tip opening21b.Such smooth transition may reduce or eliminate the likelihood of the juncture between tip end20band a guide wire getting stuck or caught up, or pushing tissue forward, asinner penetrator14bis advanced within the body.
• The tapered inner diameter ID_iptmay provide for a tight or close fit attip end20bwith a guide wire running through opening22bofinner penetrator14b.In some embodiments, the tapered inner diameter ID_iptprovides for an interference fit betweeninner penetrator14band a guide wire, at least attip end20bofinner penetrator14b.
• In addition, the length oftip transition region36b,denoted as length “L_ipt,” compared to wall thickness T_ipt, inner diameter ID and/or outer diameter OD, may be selected to provide desired flexibility oftip transition region36b.For example, the ratio of the length L_iptto wall thickness T_iptat the thickest point may be greater than or approximately equal to 20 to 1. As another example, the ratio of the length L_iptto outer diameter OD_iptmay be greater than or approximately equal to 2.5 to 1. Such configuration and dimensions may provide desired flexibility fortip transition region36b.
• The wall thickness ofmiddle transition region37b,denoted as thickness “T_ipm,” which remains substantially constant along the length ofmiddle transition region37b,may be less than or approximately equal to 0.02 inches. In a particular embodiment, wall thickness T_ipmis approximately 0.010 inches. Such configuration and dimensions may provide desired flexibility formiddle transition region37b.
• In addition, the length ofmiddle transition region37b,denoted as length “L_ipm,” compared to wall thickness T_ipm, the inner diameter and/or the outer diameter ofmiddle transition region37b,may be selected to provide desired flexibility ofmiddle transition region36b.For example, the ratio of the length L_ipmto wall thickness T_ipmmay be greater than or approximately equal to 30 to 1. As another example, the ratio of the length L_ipmto the outer diameter ofmiddle transition region37bmay be greater than or approximately equal to 3 to 1. Such configuration and dimensions may provide desired flexibility formiddle transition region37b.
• The total length oftip transition region36bandmiddle transition region37b(L_ipt+L_ipm) compared to the wall thickness at the thickest point alongtransition regions36band37bor compared to the inner diameter and/or the outer diameter ofmiddle transition region37b,may be selected to provide desired flexibility ofmiddle transition region36b.For example, the ratio of the total length oftip transition region36bandmiddle transition region37b(L_ipt+L_ipm) to the wall thickness T_ipmmay be greater than or approximately equal to 40 to 1. As another example, the ratio of the total length oftip transition region36bandmiddle transition region37b(L_ipt+L_ipm) to the outer diameter ofmiddle transition region37bmay be greater than or approximately equal to 5 to 1. Such configuration and dimensions may provide desired flexibility fortip portion25bofinner penetrator14b.The relatively long nose provided bytip transition region36bandmiddle transition region37bmay provide more flexibility than a tip having a substantially uniform taper frombody portion18bto thetip end20bofinner penetrator14b,which flexibility may be desirable for navigatinginner penetrator14balong a guide wire, for example.
• Although the embodiment shown inFIG. 2E includes threetransition regions26b,it should be understood that other embodiments may include more or less than threetransition regions26b(which may or may not include one ormore transition regions26bsimilar totransition regions36b,37band/or38bshown inFIG. 2E), or zerotransition regions26b.
• In the embodiment shown inFIG. 2E, wheninner penetrator14bis fully advanced within (and/or locked together with)outer sheath12b,a portion of thebody portion18bofinner penetrator14bmay protrude out throughtip end29bofouter sheath12b.As discussed below,tip portion30bofouter sheath12bmay be tapered to provide a relatively smooth transition between tip end29bandbody portion18bofinner penetrator14bprotruding throughtip end29b.In other embodiments,body portion18bofinner penetrator14bmay not protrude throughtip end29bofouter sheath12bwheninner penetrator14bis fully advanced within (and/or locked together with)outer sheath12b.In one embodiment,tip end29bmay substantially align with the intersection ofbody portion18bandbody transition region38bofinner penetrator14b.
• FIGS. 2F-2H illustrates a detailed view ofbody portion31bandtip portion30bofouter sheath12bofintroducer10bin accordance with one embodiment of the invention. In particular,FIG. 2F is a partial side view ofouter sheath12b,FIG. 2G is an end view ofouter sheath12b,andFIG. 2H is a cross-sectional view taken along the length ofbody portion31bofouter sheath12b.
• Body portion31bhas a substantially oval or oblong cross-section extending along the length ofbody portion31b.Tip portion30bhas a substantially oval or oblong cross-section that tapers in the direction from the endadjacent body portion31btowardtip end29b.The cross-section oflumen28bat thetip end29bofouter sheath12bmay substantially conform to the exterior cross-section ofbody portion18bofinner penetrator14b.
• In some embodiments, the materials and dimensions ofbody portion31band/ortip portion30bofouter sheath12bmay be selected to provide some degree of flexibility toouter sheath12bsuch thatouter sheath12bmay flex around particular features in the body, and such that whenintroducer10bis advanced along a guide wire,outer sheath12b(along withinner penetrator14b) may flex to substantially follow curvatures in the guide wire such that the guide wire is not significantly displaced by the advancingintroducer10.
• For example, as shown inFIG. 2F, the wall thickness oftip portion30b,denoted as thickness “T_ost,” which may be substantially uniform around the cross-sectional perimeter oftip portion30b,may decrease towardtip end29b.In some embodiments, the wall thickness T_ostoftip portion30bis less than or approximately equal to 0.03 inches at its thickest point alongtip portion30band/or less than 0.02 inches attip end29b.In a particular embodiment, the wall thickness T_ostis between approximately 0.007 inches and approximately 0.018 inches around the cross-sectional perimeter attip end29b.The decreased wall thickness, T_ost, oftip portion30btowardtip end29bmay provide for increased flexibility oftip portion30b.
• In addition, as shown inFIG. 2F, the perimeter and/or cross-sectional area oflumen28bmay decrease or taper towardtip end29b.In particular, in embodiments in whichouter sheath12b,includingtip portion30b,has an oval or oblong cross-section (such as shown inFIGS. 2G and 2H), both the horizontal inner diameter “ID_osth” and the horizontal outer diameter, “OD_osth” oftip portion30b,and both the vertical inner diameter “ID_stv” and the vertical outer diameter “OD_ostv” oftip portion30bmay decrease or taper towardtip end29b.The terms “horizontal” and “vertical” are used merely for illustrative purposes ofFIGS. 2F-2G, asouter sheath12bmay be positioned in any orientation.
• The tapered outer diameters OD_osthand OD_ostvand reduced wall thickness, T_ost, attip end29bmay provide a relatively smooth transition between tip end29bandbody portion18bofinner penetrator14b(better illustrated inFIG. 2E). Such smooth transition may reduce or eliminate the likelihood of the juncture betweenouter sheath12bandinner penetrator14bgetting stuck or caught up, or pushing tissue forward, asintroducer10bis advanced within the body.
• The taperedlumen28b(e.g., tapered inner diameters ID_osthand ID_ostv) may provide for a tight or close fit attip end29bofouter sheath12bwith the outer surface ofbody portion18bofinner penetrator14b,such thatinner penetrator14bmay be held substantially in place byouter sheath12b.In some embodiments, the taperedlumen28bprovides for an interference fit betweenouter sheath12bandinner penetrator14b,at least attip end29bofouter sheath12b.
• In addition, the length oftip portion30b,denoted as length “L_ost,” compared to wall thickness T_ost, inner diameters ID_osthand ID_ostvand/or outer diameters OD_osthand OD_ostv, may be selected to provide desired flexibility oftip portion30b.For example, the ratio of the length L_ostto wall thickness T_ostat the thinnest point may be greater than or approximately equal to 10 to 1. Such configuration and dimensions may provide desired flexibility fortip portion30b.
• The wall thickness ofbody portion31b,denoted as thickness “T_osm,” which remains substantially constant along the length ofbody portion31b,may be less than or approximately equal to 0.03 inches. In a particular embodiment, wall thickness T_osmis approximately 0.024 inches. Such configuration and dimensions may provide desired flexibility formiddle transition region37b.
• FIGS. 3A-3F illustrate an example method of implanting a paddle style electrical stimulation lead into a human's epidural space using an example introducer10 (such asintroducer10aorintroducer10b,for example).Spinal cord47 is also shown. A location between two vertebrae is selected for the procedure. The site may be selected using fluoroscopy. The first step in performing the procedure is to insertneedle41, preferably at an angle, into the skin, and through the subcutaneous tissue and ligamentum flavum44 of the spine, and into a human'sepidural space40. In one embodiment of the method, for example, the introducer might be inserted at an angle of approximately thirty-five to approximately forty-five degrees.FIG. 3A illustrates insertion ofneedle41 through the skin betweenspinous processes42 of twovertebrae43. Entry intoepidural space40 byneedle41 may be confirmed using standard methods such as the “loss-of-resistance” technique afterstylet45, or inner portion ofneedle41, is removed.
• After removingstylet45 fromneedle41,guide wire46 may be inserted throughneedle41 intoepidural space40, shown inFIG. 3B. A guide wire is used in a preferred embodiment of the method of insertion but is not required to insert a paddle style lead through the introducer. This part of the procedure may be performed under fluoroscopic guidance for example. Fluoroscopy may be used to check the position ofguide wire46 inepidural space40 before insertingintroducer10. In some embodiments, a removable stylet may be inserted into a channel extending within and along the length ofguide wire46 and manipulated by the operator in order to help steerguide wire46 into position. The stylet may also provide additional rigidity to guidewire46, which may be desired in particular applications. Once the tip ofguide wire46 is in position withinepidural space40,needle41 is removed. If a stylet was inserted intoguide wire46 as discussed above, the stylet may or may not be removed. For example, the stylet may be left inguide wire46 in order to increase the rigidity or strength ofguide wire46 in order to resistguide wire46 being moved by the advancement ofintroducer10, as discussed below.
• As shown inFIG. 3C,introducer10 may then be inserted, preferably at an angle of approximately thirty-five to approximately forty-five degrees, although the exact angle may differ depending on technique and a patient's anatomy, overguide wire46 and intoepidural space40 usingguide wire46 as a guide. The technique of passingintroducer10 overguide wire46 helps ensure proper placement ofintroducer10 intoepidural space40 and helps avoid inadvertent passage ofintroducer10 into an unsuitable location. The operator may choose to cut the skin around the insertion site with a scalpel to facilitate subsequent entry ofintroducer10 through the needle entry site. As discussed above, a stylet withinguide wire46 may increase the rigidity ofguide wire46 to resistguide wire46 being moved or dislocated byintroducer10 as introducer10 advances alongguide wire46. In some embodiments, asintroducer10 advances along flexures inguide wire46, the tip ofinner penetrator14 and/or all or portions ofouter sheath12 may flex to maneuver around obstructions or physical structures in the body (such as aspinous process42,vertebrae43, or any other structure in the body) and/or to substantially follow curvatures inguide wire46, rather than displacing portions ofguide wire46, which may cause damage to the body. An example of such flexing is shown and discussed below with reference toFIGS. 7A-7D.
• Asintroducer10 is passed through the skin it elongates the hole in the skin made byneedle41. Asintroducer10 is passed deeper into the paravertebral tissues, it spreads the fibers of tissue, muscle and ligamentum flavum44 and forms a tract through these tissues and intoepidural space40, preferably without cutting the tissues. At the level in the tissues whereintroducer10 meets and penetrates ligamentum flavum44 there is a second loss of resistance wheninner penetrator14 has completely penetrated theligamentum flavum44. Shoulder or ridge23 ofouter sheath12 is preferably lodged against ligamentum flavum44 during insertion of a paddle style lead.
• Onceintroducer10 has completely penetrated ligamentum flavum,inner penetrator14 andguide wire46 may be removed, leavingouter sheath12 positioned inepidural space40, as shown inFIG. 3D. As shown inFIG. 3E,paddle style lead50 may then be inserted throughouter sheath12 and positioned at an optimal vertebral level, using fluoroscopy for example, for the desired therapeutic effect. As shown inFIG. 3F,outer sheath12 may then be removed leaving onlypaddle style lead50 inepidural space40, wherepaddle style lead50 can be further manipulated if necessary to achieve a desired therapeutic effect.Paddle style lead50 may be secured by suturing it to a spinous process. In some embodiments, a removable stylet may be inserted into a channel extending within and along the length oflead50 and manipulated by the operator in order to help steerlead50 into position, such as described in U.S. Publication No. 2002/0022873, filed on Aug. 10, 2001, for example. The stylet may also provide additional rigidity to lead50, which may be desired in particular applications.
• As described above,introducer10 may be used to implantpaddle style lead50 intoepidural space40 for spinal nerve stimulation. The same or an analogous, perhaps smaller,introducer10 may be used to implant an analogouspaddle style lead50 into any appropriate region of the body for peripheral nerve stimulation. For example, such apaddle style lead50 may have anouter sheath12 and lumen28 with a width of approximately 1 mm to approximately 3 mm.
• A similar method of insertion (not expressly shown) may be used to implant a paddle style electrical stimulation lead into a human's peripheral nerve tissue. In this embodiment of the invention a site for insertion in tissue near a nerve is selected. The first step in performing the procedure is to insert a needle into the skin and through the subcutaneous tissue and into tissue near a peripheral nerve. If the needle has a stylet, it may be removed and a guide wire may be inserted through the needle and into the tissue near a peripheral nerve. A guide wire may not be required. Fluoroscopy may or may not be used to guide insertion of a guide wire into tissue near a peripheral nerve. Once the tip of the guide wire, or needle, is in the tissue near a peripheral nerve,introducer10 may be inserted, preferably at an angle that would depend on the anatomy of the body near the peripheral nerve to be stimulated. Asintroducer10 is passed through tissues, it elongates the tract made by a needle or guide wire and spreads the tissue. After positioningintroducer10 in tissue adjacent to the peripheral nerve to be stimulated,inner penetrator14 is removed. A paddle style lead may then be inserted throughouter sheath12.Outer sheath12 may then be removed leaving only the paddle style lead in position near the peripheral nerve to be stimulated.
• Now referring toFIGS. 4A and 4B, there are shown two embodiments of astimulation system200,300 in accordance with the present invention. The stimulation systems generate and apply a stimulus to a tissue or to a certain location of a body. In general terms, thesystem200,300 includes a stimulation or energy source210,310 and alead50 for application of the stimulus. The lead110 shown inFIGS. 4A and 4B is thepaddle style lead50 of the present invention.
• As shown inFIG. 4A, thestimulation system200 includes thelead50 that is coupled to the stimulation source210. In one embodiment, the stimulation source210 includes an implantable pulse generator (IPG). As is known in the art, an implantable pulse generator (IPG) is implanted within the body (not shown) that is to receive electrical stimulation from the stimulation source210. An example IPG may be one manufactured by Advanced Neuromodulation Systems, Inc., such as the Genesis® System, part numbers 3604, 3608, 3609, and 3644, or the Eon® System, part numbers 65-3716, 65-3851, and 64-1254.
• As shown inFIG. 4B, the stimulation system300 includes thelead50 that is coupled to the stimulation source310. The stimulation source310 includes a wireless receiver. As is known in the art, the stimulation source310 comprising a wireless receiver is implanted within the body (not shown) that is to receive electrical stimulation from the stimulation source310. An example wireless receiver310 may be those wireless receivers manufactured by Advanced Neuromodulation Systems, Inc., such as the Renew® System, part numbers 3408 and 3416.
• The wireless receiver (not shown) within stimulation source310 is capable of receiving wireless signals from a wireless transmitter320. The wireless signals are represented inFIG. 4B by wireless link symbol330. The wireless transmitter320 and a controller340 are located outside of the body that is to receive electrical stimulation from the stimulation source310. A user of the stimulation source310 may use the controller340 to provide control signals for the operation of the stimulation source310. The controller340 provides control signals to the wireless transmitter320. The wireless transmitter320 transmits the control signals (and power) to the receiver in the stimulation source310 and the stimulation source310 uses the control signals to vary the signal parameters of the electrical signals that are transmitted through lead110 to the stimulation site. An example wireless transmitter320 may be those transmitters manufactured by Advanced Neuromodulation Systems, Inc., such as the Renew® System, part numbers 3508 and 3516.
• As will be appreciated, the connectors are not visible inFIGS. 4A and 4B because the contact electrodes are situated within a receptacle (not shown) of the stimulation source210,310. The connectors are in electrical contact with a generator (not shown) of electrical signals within the stimulation source210,310. The stimulation source210,310 generates and sends electrical signals via thelead50 to the electrodes160. Understandably, the electrodes160 are located at a stimulation site (not shown) within the body that is to receive electrical stimulation from the electrical signals. A stimulation site may be, for example, adjacent to one or more nerves in the central nervous system (e.g., spinal cord) or peripheral nerves. The stimulation source210,310 is capable of controlling the electrical signals by varying signal parameters (e.g., intensity, duration, frequency) in response to control signals that are provided to the stimulation source210,310.
• As described above, once lead110 is inserted into either the epidural space or near the peripheral nerve,introducer10 is removed. Lead110 extends from the insertion site to the implant site (the area of placement of the generator). The implant site is typically a subcutaneous pocket that receives and houses the IPG or receiver (providing stimulation source210,310). The implant site is usually positioned a distance away from the stimulation site, such as near the buttocks or other place in the torso area. In most cases, the implant site (and insertion site) is located in the lower back area, and lead110 may extend through the epidural space (or other space) in the spine to the stimulation site (e.g., middle or upper back, neck, or brain areas). Once the system is implanted, the system of leads and/or extensions may be subject to mechanical forces and movement in response to body movement.FIG. 5 illustrates the steps that may be used to implant astimulation system200,300 into a human.
• FIGS. 6A-6E illustrate an example method of removing an implanted paddle style electrical stimulation lead50 from a human'sepidural space40 usingintroducer10baccording to one embodiment of the invention. Such method may be used to remove anelectrical stimulation lead50 for any suitable reason, such as to relocate, replace, or repair thelead50, for example. As discussed below, the method may be particularly advantageous for removing alead50 around which tissue may have grown and is thus firmly secured within the body. Although the method is discussed with reference tointroducer10b,the method may be similarly performed using any suitable introducer, such asintroducer10a,for example.
• As shown inFIG. 6A, a paddle styleelectrical stimulation lead50 having abody portion52 and a stimulatingportion54 may be implanted in a human'sepidural space40 in order to stimulate a nerve, such as discussed above regarding the method shown inFIGS. 3A-3F, for example. Anend56 oflead50 extends out of theepidural space40 and, in some cases, out through the person's skin or into a subcutaneous pocket formed during implantation.Introducer10b,includinginner penetrator14binserted intoouter sheath12b,may be inserted aroundbody portion52 oflead50 such thatend56 oflead50 runs thoughinner channel22bofinner penetrator14b.As shown inFIG. 6A,introducer10bmay be advanced such thatend56 oflead50 protrudes through opening26binhandle portion16bofinner penetrator14b.
• As shown inFIG. 6B, in some embodiments or situations, astylet400 may be inserted into a channel that extends along the length oflead50, if appropriate. For example,stylet400 may be a stylet typically used for guidinglead50 during the positioning oflead50 within the body.Stylet400 may be advanced partially or completely along the length oflead50, and may be advanced into stimulatingportion54 oflead50. As discussed below,stylet400 is inserted intolead50 in order to increase the rigidity oflead50 such that when theintroducer10badvances along flexures inbody portion52 oflead50,tip region25bofinner penetrator14band/or other portions ofintroducer10bmay flex to substantially follow the flexures inbody portion52 oflead50.
• As shown inFIG. 6C,introducer10bmay be advanced alongbody portion52 oflead50 untiltip region25bofinner penetrator14bis adjacent with, or comes into contact with, stimulatingportion54 oflead50. As it advances,introducer10bmay separate tissue frombody portion52 oflead50, such as tissue that may have formed aroundbody portion52 over time, thus creating a passageway through the body. In situations in whichbody portion52 extends out through the skin, the operator may choose to cut the skin around the entry point oflead50 with a scalpel to facilitate subsequent entry ofintroducer10. In addition, asintroducer10badvances along flexures inbody portion52 oflead50, due at least in part to the added strength added to lead50 bystylet400,tip region25bofinner penetrator14band/or all or portions ofouter sheath12bmay flex to maneuver around obstructions or physical structures in the body (such as aspinous process42,vertebrae43, or any other structure in the body) and/or to substantially follow curvatures inbody portion52 oflead50, rather than displacing portions oflead50, which may cause damage to the body or lead50. An example of such flexing is shown and discussed below with reference toFIGS. 7A-7D. In some embodiments, this part of the procedure may be performed under fluoroscopic guidance. For example, fluoroscopy may identify radio-opaque markers34band35boninner penetrator14bandouter sheath12b,as well as radio-opaque portions oflead50, such that the operator (e.g., doctor) may determine the relative positions ofintroducer10band lead50 during the procedure.
• As shown inFIG. 6D, whenintroducer10bhas been advanced untilinner penetrator14bis adjacent with or contacting stimulatingportion54 oflead50,outer sheath12bmay be advanced forward (e.g. by sliding) relative toinner penetrator14buntilouter sheath12bcovers at least a portion ofstimulation portion54 oflead50.Outer sheath12bmay be advanced forward until it completely coversstimulation portion54 oflead50. Advancingouter sheath12boverstimulation portion54 may separate tissue from stimulatingportion54, such as tissue that may have grown attached to stimulatingportion54. In some embodiments, this part of the procedure may be performed under fluoroscopic guidance. For example, fluoroscopy may identify radio-opaque markers34band35boninner penetrator14bandouter sheath12b,as well as radio-opaque portions oflead50, such that the operator (e.g., doctor) may determine the relative positions ofinner penetrator14b,outer sheath12b,and stimulatingportion54 oflead50 during the procedure.
• As shown inFIG. 6E,inner penetrator14b,outer sheath12b,and lead50 may all be removed together through the passageway created by advancingintroducer10balonglead50, as discussed above regardingFIG. 6C. In this manner, lead50 may be removed from the body without causing significant damage to the body or to thelead50. As discussed above, the method may be particularly advantageous for removing alead50 around which tissue may have grown and is thus firmly secured within the body.
• FIGS. 7A-7D illustrate example views ofintroducer10bflexing as it moves along aguide wire46 orstimulation lead50 within the body, in accordance with certain embodiments of the invention. In particular, all or portions oftip portion25bofinner penetrator14bmay substantially flex to follow bands or curves inguide wire46 orstimulation lead50. In some embodiments, due to the relative shapes and dimensions (e.g., the relative wall thicknesses) oftip transition region36b,middle transition region37b,andbody transition region38b,tip transition region36bmay be the most flexible, followed bymiddle transition region37b,followed bybody transition region38b.In addition, in some embodiments, such as whereouter sheath12bis formed from a polymer, all or portions ofouter sheath12bmay also flex to partially or substantially follow curvatures inguide wire46 orstimulation lead50, such as shown inFIGS. 7C and 7D, for example.
• Such flexibility ofinner penetrator14band/orouter sheath12bmay provide several advantages, as discussed above. First, such flexibility may be advantageous for navigatingintroducer10binto particular regions in the body, such as the epidural region, for example, which may also reduce the likelihood ofintroducer10bdamaging tissue in the body. Also, such flexibility may partially or substantially preventintroducer10bfrom displacingguide wire46 asintroducer10bmoves along guide wire46 (which displacement may disrupt the lead insertion or removal process and/or damage tissue in the body.
• FIG. 8 illustrates an examplelead introducer kit500 for preparing to implant an electrical stimulation lead for electrical stimulation of nerve tissue in a human, according to one embodiment of the invention. Generally,lead introducer kit500 includes a lead blank502 and one or more various tools or accessories for preparing for implanting an actual electrical stimulation lead into a human body. The lead blank502 may be used, for example, to determine whether an actual electrical stimulation lead to be implanted will fit into the target location in the body. For example, an electrical stimulation lead may not fit into the epidural space due to scar tissue or other blockages within the epidural space. Thus, if it is determined using lead blank502 that an electrical stimulation lead will not fit into the target location in the body, the electrical stimulation lead need not be removed from its packaging, thus allowing the electrical stimulation lead to be used on another patient or at a later time. This may be advantageous due to the relatively high cost of some electrical stimulation leads.
• In the embodiment shown inFIG. 8,lead introducer kit500 includes lead blank502, aneedle504, and aguide wire506, and alead introducer508. Leadintroducer kit500 may include other tools or accessories for preparing to implant an electrical stimulation lead, but in preferred embodiments does not include the actual electrical stimulation lead. Lead blank502 may have an identical or similar shape and size as an electrical stimulation lead to be inserted into the body for electrical stimulation of nerve tissue. As discussed above, lead blank502 may be configured for insertion into the human body to determine whether the electrical stimulation lead may be inserted into the desired location proximate the nerve tissue to be stimulated. For example, lead blank502 may be configured for insertion into the human body using the various methods and/or devices discussed herein, or using any other known methods and/or devices.
• Lead blank502 may include aremovable stylet510 which may be used for steering lead blank502 during insertion and/or positioning of lead blank502.Stylet510 may be inserted into a channel extending within lead blank502 and manipulated by an operator in order to help steer lead blank502. In addition, in some embodiments, the shape of lead blank502 may be configured to facilitate steering of lead blank502. For example, lead blank502 may be a paddle shape with one or more indentions, notches, or score lines that may increase the flexibility of lead blank502. For instance,FIG. 9 illustrates an example lead blank502 including apaddle style portion514 having a scalloped shape. The scalloped shape may increase the flexibility and steerability of lead blank502.
• Needle504 may include any needle suitable for insertingguide wire506 into a desired location in the body, such as a human's epidural space, for example, such asneedle41 discussed above regarding the method ofFIGS. 3A-3F.Needle504 may include aremovable stylet516, such asstylet45 discussed above, for example.
• Leadintroducer508 may include any one or more devices for inserting lead blank502 into the human body. In some embodiments,lead introducer508 may compriseintroducer10 orintroducer10bdescribed herein, or any other suitable lead introducer. Thus, in some embodiments,lead introducer508 may include anouter sheath530 and aninner penetrator532.Outer sheath530 may be inserted into a human body near nerve tissue to be stimulated.Inner penetrator532 may be removably housed withinouter sheath530 and may include an inner channel configured to receive and be advanced alongguide wire506 to a desired location relative to the nerve tissue to be stimulated.Inner penetrator532 may then be removed fromouter sheath530, leavingouter sheath530 substantially in position for insertion (or attempted insertion) of lead blank502 through the outer sheath to determine whether an actual electrical stimulation lead may be properly inserted into position proximate the nerve tissue to be stimulated. Thus, as discussed above, if lead blank502 will not fit into the target location in the body, it may be determined that the actual electrical stimulation lead will similarly not fit into the target location. Thus, the electrical stimulation lead, which may be included in a separate kit or otherwise packaged separately fromlead introducer kit500, need not be removed from its packaging, thus avoiding wasting an electrical stimulation lead, which may be relatively expensive.
• FIG. 10 illustrates an example paddle style electrical stimulation lead50ahaving electrodes on only one side, and markings indicating the directional orientation of the lead50a,according to one embodiment of the invention. Paddle style lead50amay include any suitable number ofelectrodes160a.Electrodes160amay be flat electrodes that emit energy out of only of the two sides.Such electrodes160amay be desirable for very small paddle leads, for example. Since theelectrodes160aemit energy out of only one side, the orientation (i.e., which side is facing in which direction) of the paddle style lead50amay be important, particularly when implanting the lead50aadjacent the target nerve tissue.
• Thus, lead50amay include one ormore markers550 that may be detected by one or more medical imaging techniques (such as ultrasound, fluoroscopy, MRI, fMRI and/or X-ray, for example) to indicate the directional orientation of the lead50a.For example, lead50amay include one or more radio-opaque markers550 having particular shapes or relative locations such that the operator may determine the orientation of the lead50a.
• FIG. 11 illustrates an example paddle styleelectrical stimulation lead50bhaving a substantially uniform paddle-shaped cross-section extending along the body of thelead50b,according to one embodiment of the invention.Paddle style lead50bincludes abody portion52band a stimulatingportion54b,and a number ofelectrodes160blocated at stimulatingportion54b.The cross-section of paddlestyle stimulating portion54b,which may be, for example, a substantially oval, oblong, or rectangular cross-section, may substantially extend along all or at least a significant portion of the length ofbody portion52b.In some embodiments, the substantially uniform cross-section may extend at least to a point outside the epidural region, or outside the skin. In particular embodiments, the substantially uniform cross-section may extend all the way back to the stimulation or power source. This uniform cross-section may make it easier to removelead50bfrom a human body as compared with leads having a smaller cross-sectioned lead body. For example, epidural tissue may grow around an implanted lead body over time. Such tissue may impede the removal of traditional paddle style leads. The substantially uniform cross-section ofpaddle style lead50bprevents or reduces the ability of such tissue to impede the removal of implantedlead50bfrom the body.
• FIG. 12 illustrates an example paddle styleelectrical stimulation lead50chaving a tear away body portion, according to one embodiment of the invention.Paddle style lead50cmay be similar to paddlestyle lead50bshown inFIG. 11. In particular,paddle style lead50cmay includes abody portion52c,a stimulatingportion54c,a number ofelectrodes160clocated at stimulatingportion54c,and a substantially uniform cross-section (such as a substantially oval, oblong, or rectangular cross-section, for example) extending back alongbody portion52c.Body portion52cmay include a tear-awayportion560 that may be torn away or otherwise removed, revealing a small cross-sectioned lead body (such as a standard lead body wire or cord, for example) that may extend back to the stimulation or power source. Tear-away portion560 is indicated by perforated tear lines562. However, tear-awayportion560 may have any other configuration and may be removed in any other suitable manner. In some embodiments, such as shown inFIG. 12, the distance from stimulatingportion54cto tear-awayportion560 may be selected or designed such that when lead50cis implanted in the body, the forward edge of tear-awayportion560 may be located near or just outside theepidural region562, or the skin. Thus, lead50cmay provide the advantage of being relatively easy to remove from the body (due to the substantially uniform cross-section, as discussed above), as well as providing a smaller, moremanageable body portion54cleading back to the stimulation or power source.
• Although the present invention has been described with several embodiments, a number of changes, substitutions, variations, alterations, and modifications may be suggested to one skilled in the art, and it is intended that the invention encompass all such changes, substitutions, variations, alterations, and modifications as fall within the spirit and scope of the appended claims.

Claims (16)

1. A method of implanting an electrical stimulation lead in a minimally invasive percutaneous manner to enable electrical stimulation of a human's spinal nerve tissue, comprising:

inserting a needle into the epidural space;

inserting a guide wire through the needle until an end of the guide wire is positioned in the epidural space at a desired location relative to the spinal nerve tissue to be stimulated;

removing the needle and leaving the guide wire substantially in position;

advancing an introducer, the introducer comprising an sheath and a penetrator removably housed within the sheath, the penetrator of the introducer comprising a channel configured to accommodate the guide wire and further comprising a body portion and a flexible tip portion with the tip portion configured to extend beyond the sheath, the tip portion having at least three transition regions for providing a transition between the body portion and the tip portion, along the guide wire until an end of the penetrator of the introducer is positioned in the epidural space at a desired location with respect to the spinal nerve tissue to be stimulated, the sheath of the introducer forming a tract as the penetrator of the introducer advances along the guide wire;

removing the guide wire and the penetrator of the introducer and leaving the sheath of the introducer substantially in position; and

inserting the electrical stimulation lead through the sheath of the introducer until the electrical stimulation lead is positioned in the epidural space proximate the spinal nerve tissue to be stimulated.

2. The method ofclaim 1, wherein the three transition regions of the tip portion include a flexible tip region at the end of the tip portion, a middle region next to the tip region and the body region intermediate the middle region and the body portion.

3. The method ofclaim 2, wherein the tip region has a substantially circular cross-section extending along the length of the tip region.

4. The method ofclaim 3, wherein the tip region tapers from the middle region towards the end of the tip region.

5. The method ofclaim 4, wherein the middle region has a substantially circular and constant cross-section extending the length of the middle region.

6. The method ofclaim 5, wherein the body region tapers from the body toward the middle region at angle greater that the taper of the tip region.

7. The method ofclaim 6, wherein the cross section of the body region and the sheath have cross-sections of the same shape.

8. The method ofclaim 6, wherein the body region transitions from a substantially oval-cross-section adjacent the body to a substantially circular cross-section adjacent the middle region.

9. A method of implanting a system to enable electrical stimulation of a human's nerve tissue, comprising:

inserting a needle into tissue proximate nerve tissue to be stimulated;

inserting a guide wire through the needle until an end of the guide wire is positioned at a desired location relative to nerve tissue to be stimulated;

removing the needle and leaving the guide wire substantially in position;

advancing along a guide wire an introducer, the introducer comprising an sheath and a penetrator removably housed within the sheath, the penetrator of the introducer comprising a channel configured to accommodate the guide wire and further comprising a body portion and a flexible tip portion with the tip portion configured to extend beyond the sheath, the tip portion having at least three transition regions for providing a transition between the body portion and the tip portion, along the guide wire until an end of the penetrator of the introducer is positioned in the epidural space at a desired location with respect to the spinal nerve tissue to be stimulated, the sheath of the introducer forming a tract as the penetrator of the introducer advances along the guide wire;

removing the guide wire and the penetrator of the introducer and leaving the sheath of the introducer substantially in position;

inserting an electrical stimulation lead through the sheath of the introducer until the electrical stimulation lead is positioned proximate the nerve tissue to be stimulated;

removing the outer sheath;

connecting the electrical stimulation lead to a generator; creating a subcutaneous pocket for a generator; and

inserting the generator into the subcutaneous pocket.

10. The method ofclaim 9, wherein the three transition regions of the tip portion include a flexible tip region at the end of the tip portion, a middle region next to the tip region and the body region intermediate the middle region and the body portion.

11. The method ofclaim 10, wherein the tip region has a substantially circular cross-section extending along the length of the tip region.

12. The method ofclaim 11, wherein the tip region tapers from the middle region towards the end of the tip region.

13. The method ofclaim 12, wherein the middle region has a substantially circular and constant cross-section extending the length of the middle region.

14. The method ofclaim 13, wherein the body region tapers from the body toward the middle region at angle greater that the taper of the tip region.

15. The method ofclaim 14, wherein the cross section of the body region and the sheath have cross-sections of the same shape.

16. The method ofclaim 14, wherein the body region transitions from a substantially oval-cross-section adjacent the body to a substantially circular cross-section adjacent the middle region.

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