Collapsible/expandable tubular electrode leads
A medical lead and method of treating a patient are provided. The medical lead comprises an electrically insulative tubular membrane, a resilient spring element associated with the insulative membrane, and at least one electrode associated with the insulative membrane. In the preferred embodiment, the tubular membrane has a non-circular cross-sectional shape. The spring layer is configured to urge that insulative membrane into an expanded geometry. The medical lead is configured to be collapsed into a compact form for percutaneous delivery into the patient, thereby obviating the need to perform an invasive surgical procedure on the patient. The body formed by these elements, when expanded, can be sized to fit within the epidural space of a patient. The patient can be treated by placing the medical lead into a collapsed state by applying a compressive force to the medical lead, percutaneously delivering the collapsed medical lead into the patient adjacent tissue to be treated, and placing the medical lead into an expanded state by releasing the compressive force. In one preferred method, the stimulation lead is used to stimulate tissue, such as spinal cord tissue.
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This application is related to copending U.S. patent application Ser. No. 10/______ (attorney docket number 30-7038142001), filed on the same date, and expressly incorporated herein by reference.
FIELD OF THE INVENTIONThe invention relates to the implantation of electrode leads within a patient, and in particular, the implantation of stimulation electrode leads within a patient's spine to treat disorders, such as chronic pain.
BACKGROUND OF THE INVENTIONIt is known to treat chronic pain by electrically stimulating the spinal cord, spinal nerve roots, and other nerve bundles. Although not fully understood, the application of electrical energy to particular regions of the spinal cord induces parasthesia (i.e., a subjective sensation of numbness or tingling) in the afflicted body regions associated with the stimulated spinal regions. This parasthesia effectively masks the transmission of chronic pain sensations from the afflicted body regions to the brain. Since each body region is associated with a particular spinal nerve root, it is important that stimulation be applied at the proper longitudinal position along the spinal cord to provide successful pain management and avoid stimulation of unaffected regions of the body. Also, because nerve fibers extend between the brain and the nerve roots along the same side of the spine as the body regions they control, it is equally important that stimulation be applied at the proper lateral position of the spinal cord. For example, to treat unilateral pain (i.e., pain sensed only on one side of the body), electrical stimulation is applied to the corresponding side of the spinal cord. To treat bilateral pain (i.e., pain sensed on both sides of the body), electrical stimulation is either applied directly to the midline of the spinal cord or applied to both lateral sides of the spinal cord.
In a typical procedure, one or more stimulation leads are introduced through the patient's back into the epidural space under fluoroscopy. The specific procedure used to implant the stimulation lead will ultimately depend on the type of stimulation lead used. Currently, there are two types of commercially available stimulation leads: a percutaneous lead and a surgical lead.
A percutaneous lead comprises a cylindrical body with ring electrodes, and can be introduced into contact with the affected spinal tissue through a Touhy-like needle, which passes through the skin, between the desired vertebrae, and into the spinal cavity above the dura layer. For unilateral pain, a percutaneous lead is placed on the corresponding lateral side of the spinal cord. For bilateral pain, a percutaneous lead is placed down the midline of the spinal cord, or two percutaneous leads are placed down the respective sides of the midline.
A surgical lead has a paddle on which multiple electrodes are arranged in independent columns, and is introduced into contact with the affected spinal tissue using a surgical procedure, and specifically, a laminectomy, which involves removal of the laminar vertebral tissue to allow both access to the dura layer and positioning of the lead.
After the stimulation lead(s) (whether percutaneous or surgical) are placed at the target area of the spinal cord, the lead(s) are anchored in place, and the proximal ends of the lead(s), or alternatively lead extensions, are passed through a tunnel leading to a subcutaneous pocket (typically made in the patient's abdominal area) where a neurostimulator is implanted. The lead(s) are connected to the neurostimulator, which is then operated to test the effect of stimulation and adjust the parameters of the stimulation for optimal pain relief. During this procedure, the patient provides verbal feedback regarding the presence of paresthesia over the pain area. Based on this feedback, the lead position(s) may be adjusted and re-anchored if necessary. Any incisions are then closed to fully implant the system.
Various types of stimulation leads (both percutaneous and surgical), as well as stimulation sources and other components, for performing spinal cord stimulation are commercially available from Medtronic, Inc., located in Minneapolis, Minn., and Advanced Neuromodulation Systems, Inc., located in Piano, Tex.
The use of surgical leads provides several functional advantages over the use of percutaneous leads. For example, the paddle on a surgical lead has a greater footprint than that of a percutaneous lead. As a result, an implanted surgical lead is less apt to migrate from its optimum position than is an implanted percutaneous lead, thereby providing a more efficacious treatment and minimizing post operative procedures otherwise required to reposition the lead. As another example, the paddle of a surgical lead is insulated on one side. As a result, almost all of the stimulation energy is directed into the targeted neural tissue. The electrodes on the percutaneous leads, however, are entirely circumferentially exposed, so that much of the stimulation energy is directed away from the neural tissue. This ultimately translates into a lack of power efficiency, where percutaneous leads tend to exhaust a stimulator battery supply 25%-50% greater than that exhausted when surgical leads are used. As still another example, the multiple columns of electrodes on a surgical lead are well suited to address both unilateral and bilateral pain, where electrical energy may be administered using either column independently or administered using both columns.
Although surgical leads are functionally superior to percutaneous leads, there is one major drawback—surgical leads require painful surgery performed by a neurosurgeon, whereas percutaneous leads can be introduced into the epidural space minimally invasively by an anesthesiologist using local anesthesia.
There, thus, remains a need for a minimally invasive means of introducing stimulation leads within the spine of a patient, while preserving the functional advantages of a surgical lead.
SUMMARY OF THE INVENTIONIn accordance with a first aspect of the present inventions, a medical lead is provided. The medical lead comprises an electrically insulative tubular membrane having an inner surface and an outer surface, a resilient spring element, and at least one electrode mounted. The spring element is associated with the membrane, e.g., by forming or mounting the spring element onto the membrane, or embedding the spring element into the membrane, and the electrode(s) is associated with the outer surface of the membrane, e.g., by forming or mounting the electrode(s) onto the outer surface, or embedding the springelement into the outer surface. The spring element can be associated with the inner surface or the outer surface of the insulative membrane.
The insulative membrane can be, e.g., continuous, porous, or meshed. The insulative membrane can take on a variety of tubular shapes. For example, the tubular shape can exhibit a circular, rectangular, triangular, or irregular geometry. In one embodiment, the insulative membrane is allowed to be flaccid and has a relatively low-stiffness, so that it can be made as thin as possible to facilitate collapsing of the medical lead into a low-profile geometry. The spring element is configured to expand the insulative membrane. The spring element can be, e.g., a discrete element or can be formed of a mesh or braid.
In one embodiment, the medical lead is configured to inhibit tissue growth. If associated with the inner surface of the insulative membrane, the spring element can be formed of any suitable resilient material, since it is not exposed to tissue. If associated with the outer surface of the insulative membrane, however, the spring element is preferably formed of a material that inhibits tissue growth. For example, in this case, the spring element can be formed of a continuous layer of material. In this manner, the implanted medical lead can be more easily retrieved from the patient's body, if necessary. The medical lead is preferably configured to be collapsed into a compact form for percutaneous delivery into the patient, thereby obviating the need to perform an invasive surgical procedure on the patient. The medical lead, when expanded, can be sized to fit within the epidural space of a patient.
In accordance with a second aspect of the present inventions, another medical lead is provided. The medical lead comprises a resilient tubular structure having a normally non-circular cross-sectional shape (e.g., a rectangle, oval, or crescent), and at least one electrode associated with the tubular structure. The tubular structure may comprise, e.g., a discrete element or can be formed of a mesh or braid. In one embodiment, the medical lead is configured to inhibit tissue growth. The medical lead is preferably configured to be collapsed into a compact form for percutaneous delivery into the patient, thereby obviating the need to perform an invasive surgical procedure on the patient. The medical lead, when expanded, can be sized to fit within the epidural space of a patient. In this case, the non-cylindrical geometry of the tubular structure allows the tubular structure to conform to the non-cylindrical shaped epidural space, so that, when expanded, painful tissue displacement is minimized.
In accordance with a third aspect of the present inventions, a method of treating a patient with one of the previously described medical leads is provided. The method comprises placing the medical lead into a collapsed state by applying a compressive force to the medical lead, percutaneously delivering the collapsed medical lead into the patient adjacent tissue to be treated, and placing the medical lead into an expanded state by releasing the compressive force. In one preferred method, the medical lead is used to stimulate tissue, such as spinal cord tissue.
BRIEF DESCRIPTION OF THE DRAWINGSThe drawings illustrate the design and utility of preferred embodiment(s) of the invention, in which similar elements are referred to by common reference numerals. In order to better appreciate the advantages and objects of the invention, reference should be made to the accompanying drawings that illustrate the preferred embodiment(s). The drawings, however, depict the embodiment(s) of the invention, and should not be taken as limiting its scope. With this caveat, the embodiment(s) of the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Referring now to
It should be noted that although the kit 100 illustrated in
The stimulation lead 102 comprises an elongated sheath body 108 having a proximal end 110 and a distal end 112. The sheath body 108 is composed of a suitably flexible material (such as polyurethane, silicone, etc.), which may either be resilient or non-resilient, and may be formed via an extrusion process or by any other suitable means. In the illustrated embodiment, the sheath body 108 is cylindrically-shaped and sized to fit through a Touhy-like needle (not shown). In this case, the diameter of the sheath body 108 is preferably less than 5 mm to allow it to be percutaneously introduced through a needle. More preferably, the diameter of the sheath body 108 is within the range of 1 mm to 3 mm, so that the stimulation lead 102, along with the secondary stimulation leads 104 described below, can comfortably fit within the epidural space of the patient. The sheath body 108 may have other cross-sectional geometries, such as oval, rectangular, triangular, etc. If rectangular, the width of the stimulation lead 102 can be up to 5 mm, since the width of an epidural space is greater than its height. The sheath body 108 may have an optional lumen (not shown) for receiving an obturator (not shown) that axially stiffens the sheath body 108 to facilitate percutaneous introduction of the stimulation lead 102 within the epidural space of the patient's spine, as will be described in further detail below.
The stimulation lead 102 further comprises a plurality of terminals 114 (in this case, four) mounted on the proximal end 110 of the sheath body 108. The terminals 114 are formed of ring-shaped elements composed of a suitable biocompatible metallic material, such as platinum, platinum/iridium, stainless steel, gold, or combinations or alloys of these materials, and can be mounted to the sheath body 108 in an interference fit arrangement.
The stimulation lead 102 further comprises a stimulation paddle 116 suitably mounted to the distal end 112 of the sheath body 108. In this embodiment, the stimulation paddle 116 is laterally centered on the sheath body 108, but as will be discussed below, the electrode paddle 116 can alternatively be laterally offset from the sheath body 108. As will be described in further detail below, the stimulation paddle 116 is configured to be placed into a compact, low-profile geometry by, e.g., rolling (see
Referring further to
The electrodes 120 can be formed onto the membrane 118 using known deposition processes, such as sputtering, vapor deposition, ion beam deposition, electroplating over a deposited seed layer, or a combination of these processes. Alternatively, the electrodes 120 can be formed onto the membrane 118 as a thin sheet or foil of electrically conductive metal. Or, the electrodes 120 can be discrete elements that are embedded into the membrane 118, such that they lie flush with the surface 124 of the membrane 118. The electrodes 120 can be composed of the same electrically conductive and biocompatible material as the terminals 114, e.g., platinum, platinum/iridium, stainless steel, gold, or combinations or alloys of these materials. In the embodiment illustrated in
The stimulation lead 102 further comprises a plurality of conductors (not shown) extending through the sheath body 108 and membrane 118 and connecting each electrode 120 with a respective terminal 114. The conductors 122 are composed of a suitably electrically conductive material that exhibits the desired mechanical properties of low resistance, corrosion resistance, flexibility, and strength.
In the illustrated embodiment, the membrane 118 is composed of a continuous layer of material, although alternatively, the membrane 118 may be porous, meshed, or braided. Whether continuous or not, the material from which the membrane 118 is composed is relatively thin (e.g., 0.1 mm to 2 mm, although 1 mm or less is most preferred) and has a relatively low-stiffness. Exemplary materials are low-stiffness silicone, expanded polytetrafluoroethylene (ePTFE), or urethane. Due to these properties, the stimulation paddle 116 can be more easily collapsed into a low-profile geometry. For example, the stimulation paddle 116 can be rolled (see
The skeletal spring element 122, however, advantageously provides this necessary spring force. In particular, the spring element 122 is composed of a relatively high-stiffness and resilient material, such as stainless steel, a metallic and polymer material, or a high-stiffness urethane or silicone, that is shaped into a normally planar (curviplanar) geometry. In alternative embodiments, the spring element 122 may be composed of a shape memory material, such as nitinol, so that it assumes a planar (or curviplanar) geometry in the presence of a defined temperature, such as, e.g., body temperature. Thus, it can be appreciated that the normally planar (or curviplanar) geometry of the spring element 122 will cause the stimulation paddle 116 to likewise assume a planar (curviplanar) geometry in the absence of an external force (in particular, a compressive force). In the illustrated embodiment, the spring element 122 is formed of a thin layer of material that is laminated onto the membrane 118. In effect, the spring element 122 has a two-dimensional geometry in that it has a length and a width, but a minimal thickness. As a result, protrusions from the membrane 118 are avoided, thereby allowing the stimulation paddle 116 to be placed into a lower collapsed profile. Alternatively, the spring element 122 can be made from wire, which is cylindrical in nature, and thus, can be said to have a three-dimensional geometry. Whether formed from a layer of material or a wire, the spring element 122 may alternatively be embedded into the membrane 118, so that the surface of the spring element 122 is flush with the surface 124 of the membrane 118.
As can be seen in
The spring element 122 can have other geometries. For example,
As another example,
Although all of the stimulation paddles illustrated in
In particular,
The electrodes 220 can be composed of the same material, shaped, and formed onto the membrane 218 in the same manner as the electrodes 120. In the embodiment illustrated in
Although the membrane 218 is illustrated as having a normally expanded rectangular geometry, as best shown in
Referring back to
Alternatively, the implantable stimulation source 104 may take the form of a passive receiver that receives radio frequency (RF) signals from an external transmitter worn by the patient. In this scenario, the life of the stimulation source 104 is virtually unlimited, since the stimulation signals originate from the external transmitter. Like the self-contained generators, the receivers of these types of stimulation sources 106 can be implanted within the chest or abdominal region beneath the skin of the patient. The receivers may also be suitable for implantation behind the ear of the patient, in which case, the external transmitter may be worn on the ear of the patient in a manner similar to that of a hearing aid. Stimulation sources, such as those just described, are commercially available from Advanced Neuromodulation Systems, Inc., located in Piano, Tex., and Medtronic, Inc., located in Minneapolis, Minn.
The optional extension lead 106 comprises an elongated sheath body 109 having a proximal end 111 and a distal end 113, much like the sheath body 108 of the stimulation lead 102, a proximal connector 115 coupled to the proximal end 113 of the sheath body 109, a distal connector 117 coupled to the distal end 111 of the sheath body 109, and a plurality of electrical conductors (not shown) extending through the sheath body 109 between the proximal and distal connectors 115/117. The length of the extension lead 102 is sufficient to extend from the spine of the patient, where the proximal end of the implanted stimulation lead 102 protrudes from to the implantation site of the stimulation source 104—typically somewhere in the chest or abdominal region. The proximal connector 115 is configured to be coupled with to the stimulation source 104, and the distal connector 117 is configured to mate with the proximal end of the stimulation lead 102.
Having described the stimulation lead kit 100, its installation and use in treating chronic pain will now be described with reference to
After the deliver mechanism is in place, the stimulation lead 102, with the stimulation paddle 116 collapsed into a low-profile geometry (see
Next, the needle 10 or introducer is removed, and the proximal end of the stimulation lead 102 is connected to a tester (not shown), which is then operated in a standard manner to confirm proper location of the stimulation lead 102 and to adjust the stimulation parameters for optimal pain relief. Once this optimization process has been completed, the tester is disconnected from the stimulation lead 102, which is then anchored in place using standard lead anchors (not shown). In the case of stimulation tubes 216/236, anchors may not be necessary, since they self-anchor themselves within the epidural space when expanded. Next, the stimulation lead 102 is coupled to the stimulation source 104 and implantation is completed (not shown). In particular, a subcutaneous pocket is created in the patient's abdominal area for implantation of the stimulation source 104, and a tunnel is subcutaneously formed between the spine region and the subcutaneous pocket. The optional lead extension 106 is passed through the tunnel, after which the adapter 154 of the extension 106 is connected to the proximal end of the stimulation leads 102 and the connector 156 of the lead extension 106 is connected to the stimulation source 104. The stimulation source 104 is programmed and tested, and then placed within the subcutaneous pocket, after which all incisions are closed to effect implantation of the stimulation lead 102 and stimulation source 104. The stimulation source 104 can then be operated to convey stimulation energy from the stimulation source 104 to the electrodes 120 of the stimulation lead 102, where it is, in turn, conveyed into the neural tissue for pain relief.
It can be appreciated that the relatively large footprint made by the stimulation lead 102, much like a prior art surgical lead, provides a more stable platform for the electrodes 120. Also, like a prior art surgical lead, the electrodes 120 face in a single direction, thereby focusing the stimulation energy into the affected neural tissue where it is needed. Unlike a surgical lead, however, the stimulation lead 102 can be percutaneously delivered into the patient's spine in a minimally invasive and relatively pain-free manner, without requiring extensive patient recovery.
Although particular embodiments of the present invention have been shown and described, it should be understood that the above discussion is not intended to limit the present invention to these embodiments. It will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Thus, the present invention is intended to cover alternatives, modifications, and equivalents that may fall within the spirit and scope of the present invention as defined by the claims.
Claims
1. A medical lead, comprising:
- an electrically insulative tubular membrane having an inner surface and an outer surface;
- a resilient spring element associated with the insulative membrane; and
- at least one electrode associated with the outer surface of the insulative membrane.
2. The medical lead of claim 1, wherein the insulative membrane insulative membrane has a normally non-cylindrical shape.
3. The medical lead of claim 1, wherein the insulative membrane has a first stiffness, and the spring layer has a second stiffness greater than the first stiffness.
4. The medical lead of claim 1, wherein the insulative membrane is flaccid.
5. The medical lead of claim 1, wherein the spring element is a discrete element.
6. The medical lead of claim 1, wherein the spring element is a mesh or braid.
7. The medical lead of claim 1, wherein the spring element is configured to expand the insulative membrane.
8. The medical lead of claim 1, wherein the resilient spring element is associated with the outer surface of the insulative membrane.
9. The medical lead of claim 1, wherein the resilient spring element is associated with the inner surface of the insulative membrane.
10. The medical lead of claim 1, wherein the insulative membrane, spring element, and at least one electrode form a body that is configured to inhibit tissue growth.
11. The medical lead of claim 1, wherein the insulative membrane, spring element, and at least one electrode form a body that is configured to be collapsed into a compact form for percutaneous delivery into a patient.
12. The medical lead of claim 1, wherein the insulative membrane, spring element, and at least one electrode form an expanded body that is sized to fit within the epidural space of a patient.
13. A method of performing a medical procedure on a patient, comprising:
- placing the medical lead of claim 1 into a collapsed state by applying a compressive force to the medical lead;
- percutaneously delivering the collapsed medical lead into the patient adjacent tissue to be treated; and
- placing the medical lead into an expanded state by releasing the compressive force, whereby the resilient spring element facilitates expansion of the medical lead.
14. The method of claim 13, further comprising stimulating the tissue with the medical lead.
15. The method of claim 13, wherein the tissue is spinal cord tissue.
16. A medical lead, comprising:
- a resilient tubular structure having a normally non-circular cross-sectional shape; and
- at least one electrode associated with the tubular structure.
17. The medical lead of claim 16, wherein the tubular structure comprises a discrete resilient spring element.
18. The medical lead of claim 16, wherein the tubular structure comprises a resilient mesh or braid.
19. The medical lead of claim 16, wherein the tubular structure is configured to inhibit tissue growth.
20. The medical lead of claim 16, wherein the tubular structure is configured to be collapsed into a compact form for percutaneous delivery into a patient.
21. The medical lead of claim 16, wherein the tubular structure is sized to fit within the epidural space of a patient.
22. The medical lead of claim 16, wherein the non-circular shape is a rectangle.
23. The medical lead of claim 16, wherein the non-circular shape is an oval.
24. The medical lead of claim 16, wherein the non-circular shape is a crescent-shaped.
25. A method of performing a medical procedure on a patient, comprising:
- placing the medical lead of claim 16 into a collapsed state by applying an external force to the medical lead;
- percutaneously delivering the collapsed medical lead into the patient adjacent tissue to be treated; and
- placing the medical lead into an expanded state by releasing the external force.
26. The method of claim 25, further comprising stimulating the tissue with the medical lead.
27. The method of claim 26, wherein the tissue is spinal cord tissue.
Type: Application
Filed: Mar 12, 2004
Publication Date: Sep 15, 2005
Applicant:
Inventors: Michael Wallace (Fremont, CA), Robert Garabedian (Mountain View, CA)
Application Number: 10/799,295