Abstract:
A combined electrical and chemical stimulation lead is especially adapted for providing treatment to intervertebral discs. The combination lead may be placed proximate to intervertebral disc cellular matrix and nucleus pulposus tissue to promote tissue regeneration and repair, as well as nociceptor and neural tissue modulation. The stimulation lead includes electrodes that may be selectively positioned along various portions of the stimulation lead in order to precisely direct electrical energy to stimulate the target tissue. The lead also includes a central infusion passageway or lumen that communicates with various infusion ports spaced at selected locations along the lead to thereby direct the infusion of nutrients/chemicals to the target tissue.

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to electrical stimulation leads and chemical infusion catheters for treatment of medical conditions, and more particularly, to a system, method and device for providing combined electrical stimulation and chemical/drug infusion for treatment of intervertebral disc ailments.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known that immersing certain cell types within an electrical field will cause these cells to proliferate thus facilitating tissue repair. One known use of an electrical field for such repair is “in bone” stimulators that are implanted in fractures and/or spinal fusions. Another type of treatment has recently developed for spinal conditions wherein target tissue is stimulated by an electrical lead using radio-frequency energy to induce a thermal lesion in the target tissue. In this type of procedure, the therapeutic benefit is intended to derive from heating the target tissue and not from immersing the tissue in an electric field. Thus, the electrical lead in this treatment is strictly for use in heating the tissue, and there is no therapeutic electrical field generated. Chemical treatment of target tissues has also been developed by use of various types of infusion catheters.  
         [0003]     For both electrical and thermal stimulation, an electrical current generator, commonly referred to as a pulse generator, may be used to transmit a pulse of electrical current to an implanted stimulation lead that has been precisely placed to transmit the electrical or thermal energy from the electrodes to the target tissue in order to treat the particular condition. For chemical stimulation, one or more drugs or nutrients are delivered by a pump that transfers a desired quantity and frequency of the drug/nutrient through an infusion port of the catheter to the target tissue. For chemical stimulation as well as electrical/thermal stimulation, implanted pumps and generators can be used to deliver the electrical and chemical stimulation as opposed to transdermal delivery devices. More particularly, implanted pulse generators (IPG) as well as implanted drug dispensers (IDP) are commonly used so that patients do not have to return to a medical facility each time treatment is to be conducted.  
         [0004]     One relatively new procedure has been developed to treat discogenic back pain. As an alternative to other surgical procedures for patients who suffer from back pain caused by certain types of disc disorders, this new procedure is made possible by use of thermal stimulation leads that provide precise temperature control in the delivery of thermal energy to target tissue. This procedure, commonly referred to as intradiscal electrothermal annuloplasty (IDET) was initially believed to function by cauterizing nerve endings within the disc wall to assist in reduction of pain, and the heat produced by the stimulation leads would also thicken the collagen of the disc wall thereby promoting healing of the damaged disc. Due to age, injury or other conditions, cracks or fissures may develop in the wall of the invertebral disc causing a chronic source of pain in many patients. Additionally, the inner disc tissue (nucleus) will frequently cause the disc to bulge or herniate into the fissures in the outer region of the disc, thus causing nerve tissue therein to generate pain signals. IDET has proven in some cases to be a minimally invasive procedure to treat these types of disc ailments. However, recent research, and clinical experience has cast doubt on the reasons why the procedure results in a healing response of the target tissue. It is now believed that the thermal energy imparted to the disc creates an injury pattern that in some discs results in a repair response. The results of IDET are better characterized as inconsistent and this approach is a very inefficient and marginally effective means of producing a restorative response.  
         [0005]     Combination electrical stimulators and chemical infusion catheters are known for purposes of treating various spine and brain ailments. One reference that discloses such a combination device is the invention in U.S. Publication No. US2004/0243206. This reference specifically discloses a combination electrical and stimulation lead for stimulation of a person&#39;s nerve tissue in the brain. One or more electrodes are located along the lead body and are adapted to be positioned proximate the target nerve tissue and to deliver electrical stimulation pulses transmitted through the lead to the target nerve tissue. One or more infusion ports located along the lead body are adapted for placement proximate the target nerve tissue and to deliver chemical stimulation pulses transmitted through the lead to the target nerve tissue.  
         [0006]     While combination electrical and stimulation leads may be known, special considerations must be made for use of such devices for intervertebral disc treatment.  
         [0007]     The intervertebral disc (IVD) provides separation, shock absorption, and controlled motion between vertebral bodies. The disc is comprised of a central nucleus of a semi-fluid mass of mucoid material, (nucleus pulposus), an outer more dense collagen ring (annulus fibrosis), and a thin, metabolically active cellular layer separating the nucleus and the outer collagen ring, referred to as the annular nuclear interface/transitional zone. Disc nutrition is tenuous at best and is provided by diffusion through the vertebral end plate in contact with the outer surface of the disc. As a result, a disc has limited ability to heal or regenerate.  
         [0008]     Placement of a stimulation lead within a disc can be quite difficult. Because a disc does not have a uniform density, known stimulation leads can be quite difficult to place and may require the attending physician to make multiple attempts for proper placement or abandon the procedure. Of course, multiple placement attempts greatly increase the invasive nature of the procedure and therefore create unnecessary tissue damage and increased risk. Inability to perform the procedure denies the patient a therapeutic option. Improper placement of the stimulation lead can also result in the undesirable cauterization of nerve tissue that is not contributing to the chronic pain or other ailments. Because of the overall metabolically inactive nature of the disc, it is also important that chemical infusion be precisely targeted to contact the damaged area of the disc with the delivered chemicals/nutrients otherwise inaccurate delivery to non-damaged portions of the disc can reduce the effectiveness of the procedure. Thus, there is a need for a combination electrical and chemical stimulation lead that can be precisely placed with a high rate of success on a first attempt.  
         [0009]     The IVD is also a motion segment of the body that is subjected to many flexion/extension/rotation cycles every day. In some procedures, it may be necessary to keep the stimulation lead emplaced for long periods of time, such as weeks or perhaps months. Thus, it is desirable to have a stimulation lead that maintains a small profile, yet is resilient enough to withstand the risk of permanent deformation or shearing during treatment and removal of the stimulation lead after treatment.  
         [0010]     In accordance with the present invention, a combined electrical and chemical stimulation device is provided that is especially adapted for treatment of intervertebral disc ailments. The stimulation device is in the form of a stimulation lead designed to be placed in the disc percutaneously through an introducer needle using an extra-pedicular approach; however, micro-surgical or open-surgical techniques may also be utilized. More specifically, the device of the present invention is specifically designed to facilitate placement proximate to the metabolically active cellular, nuclear, annular interface layer by use of one or more selected embodiments including a straight, curved or bent tip, as well as a variable stiffness tip. Selection of one of these embodiments allows the physician to precisely navigate the lead through the nucleus of the disc. In yet another embodiment of the present invention, the stimulation lead may be placed directly into the nuclear annular interface by use of a introducer needle having a bent tip, and use of a stimulation lead having a straight tip that can take a substantially linear path to reach the target tissue.  
         [0011]     The structure of the stimulation lead of the present invention is characterized by an elongate and tubular shaped body including one or more electrodes located along selected portions of the lead body and adapted for positioning proximate the target tissue to deliver electrical stimulation pulses transmitted through the lead. Preferably, the electrodes extend circumferentially around a selected length or portion of the lead since it is difficult to orient a specific lateral side of the lead against target tissue. One or more infusion ports are also located along the lead body and are adapted to be positioned proximate the target tissue to deliver selected chemicals/nutrients.  
         [0012]     Once the stimulation lead is correctly positioned, the lead is then connected to a pulse generator for delivery of electrical energy to the electrodes located on the distal portion of the stimulation lead, and is connected to an infusion pump that provides a controlled delivery of chemicals/nutrients through the lead to the target tissue. Preferably, the electrical pulse generator and infusion pump are implanted medical devices. These devices are also preferably refillable and rechargeable.  
         [0013]     Particular embodiments of the present invention provide one or more advantages in terms of navigation of the stimulation lead, as well as placement of the infusion ports and electrodes for effectively delivering electrical and chemical treatment. More specifically, the particular shape of the stimulation lead, as well as the particular placement of the electrodes and infusion ports are especially adapted for delivering the electrical stimulation and chemical infusion to target tissue within a disc. A stiffening or support element may be incorporated in the wall of the stimulation lead to ensure the lead does not prematurely shear or otherwise structurally fail during use and removal. The stiffening element is preferably in the form of an elongate support that extends longitudinally within the wall of the stimulation lead and terminating near the distal tip of the lead.  
         [0014]     Further advantages and features of the present invention will become apparent from a review of the following detailed description, taken in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Reference is now made to the following detailed description taken in conjunction with the accompanying drawings in order for a more thorough understanding of the present invention.  
         [0016]      FIG. 1  illustrates the system of the present invention including a stimulation lead inserted in an intervertebral disc, and a stimulation source that provides a controlled delivery of electrical field energy and chemicals/nutrients through the stimulation lead;  
         [0017]      FIG. 2  is a greatly enlarged cross-section of the working distal portion of one preferred embodiment of the stimulation lead of the present invention;  
         [0018]      FIGS. 3-7  are greatly enlarged side or elevation views illustrating other preferred embodiments of the stimulation lead;  
         [0019]      FIG. 8  is a greatly enlarged cross-section of the working distal portion of another preferred embodiment that incorporates a stiffening element;  
         [0020]      FIG. 9  is a section taken along line  9 - 9  of  FIG. 8 ;  
         [0021]      FIG. 10  illustrates another preferred embodiment of the present invention in the form of an introducer needle having a bent distal end for placement of the stimulation lead directly into the nuclear annular interface; and  
         [0022]      FIGS. 11-13  illustrate further embodiments of the present invention wherein the electrodes and infusion ports are dispersed substantially along the entire length of the stimulation lead. 
     
    
     DETAILED DESCRIPTION  
       [0023]     Referring to  FIGS. 1 and 2 , the system  10  of the present invention is shown that includes a combination electrical and chemical stimulation device  12 , a stimulation source  14  that communicates with the stimulation device  12  for delivering electrical energy and chemicals to the stimulation device, and an interventional device such as an introducer needle  32  that allows introduction of the stimulation lead into the disc. The stimulation device  12  is shown as inserted within an intervertebral disc D. The combination device  12  more particularly includes a percutaneous electrical and chemical stimulation lead  16  in the form of an elongate tubular member having a desired length and diameter allowing the lead  16  to be placed within the intervertebral disc of the patient to be treated. The working distal portion  20  of the stimulation lead  16  provides the desired stimulation through a plurality of electrodes  22  which are selectively positioned on the distal portion  20 , along with a plurality of infusion ports  30  which allow delivery of chemicals/nutrients to target tissue. The proximal portion of the stimulation device  12  can be referred to as a lead extension  18  that connects to the stimulation source  14 . The lead extension  18  can be made of the same type and diameter material as the stimulation lead  16 , or may be made of a different type of material and diameter.  
         [0024]     Referring specifically to  FIG. 2 , in a first embodiment of the stimulation lead, a plurality of circumferentially extending electrodes  22  are positioned at the distal portion  20 . The electrodes  22  are also spaced longitudinally along the distal portion  22 . The electrodes produce an array of electrical field energy, and the target tissue is immersed in the electrical field. One or more electrical conductors  23  extend through the interior of the stimulation lead  16  in order to transmit the electrical impulses to the electrodes  22 . It is preferable to utilize a single conductor  23  along the major length of the lead, and then provide branch conductors (not shown) at the distal portion  20  that then extend to contact the various electrodes. The branch conductors could be a linearly arranged set of wire extensions extending between each electrode, or any other advantage combination of wire conductors to interconnect the electrodes. Use of a single conductor is a more robust design as opposed to multiple smaller conductors that are more prone to breakage as a result of the motion cycles of the ISD. It is also contemplated that the electrodes could be a single electrode wound in a helical pattern about the distal portion  20 . Thus in this helical pattern, only one conductor  23  would be required with no additional branch conductors. In order to generate the desired intensity and size electrical field, the electrodes  22  can be disposed on the distal portion in a pattern or arrangement that best suits the electrical field to be generated. For example, in the helical pattern, the electrode could be wound with a tighter pattern to generate a more intense field, while a looser more spaced pattern would generate a less intense field. Of course, the particular signal or impulse current provided to the electrodes also determines the intensity of the field generated.  
         [0025]     In order to provide chemical infusion, a central lumen or passageway  24  is formed through the stimulation lead. The central lumen  24  may extend completely through the lead thereby forming a distal opening  28  in the stimulation lead and providing one infusion port that is directed distally of the stimulation lead.  
         [0026]     The stimulation lead  16  may be made of a homogeneous material, or may be made of differing materials that cause the stimulation lead to have either a more progressively stiff or more progressively flexible characteristic as the lead extends in the distal direction. Depending upon the manner in which the stimulation lead is to be emplaced, it may be desirable to use either the more progressively stiff or more progressively flexible arrangement.  
         [0027]     In accordance with the method of the present invention, a stylet (not shown) is first inserted through the introducer needle  32 . The introducer needle  32  is emplaced by penetrating the skin and muscle tissue, and ultimately into the disc D. When the introducer needle has penetrated the disc, the stylet is removed and the stimulation lead  16  is then inserted through the lumen of the introducer needle.  
         [0028]     Referring again to  FIG. 1 , the stimulation lead  16  is illustrated as being emplaced within the disc D. This disc D is shown in cross section along with an adjacent vertebrae V. The stimulation lead  16  is shown as taking an arcuate or curved path through the disc nucleus N in order to be precisely positioned at the area of the disc to be treated, illustrated as a fissure F which has developed adjacent the spinal fluid sac (not shown).  
         [0029]     The stimulation source  14  is preferably an implantable medical device  34  including both an IPG (implantable pulse generator)  36  and an IDP (implantable drug dispenser)  38 . The implantable device  34  could be contained within a single structural housing, or two separate housings, one for the IPG  36 , and one for the IDP  38 . The IPG and IDP can both be self-contained devices with internal control for preset delivery of electrical and chemical pulses. Alternatively, an external controller  44  could be used to modify the desired treatment protocol by use of RF transmission wherein an implantable RF receiver  40  is integrated with the IPG  36  and IDP  38 . The RF receiver  40  could also be housed within the same implantable medical device  34 , or could be a separate implanted device. An external RF transmitter  42  transmits RF signals to control the delivery of electrical stimulation and chemicals to the stimulation lead  16 . A controller  44  provides the specific instruction set for transmission by the RF transmitter  42 .  
         [0030]     Referring to  FIG. 3 , a different arrangement is illustrated with respect to the location of the electrodes  22 , and the single infusion port at distal opening  28  is supplemented with a plurality of additional infusion ports  30 . In this embodiment, fewer electrodes are incorporated, yet additional infusion ports  30  are provided that are spaced longitudinally along the length of the lead  16  and placed between the electrodes  22 .  
         [0031]      FIG. 4  shows another embodiment with a different arrangement of electrodes  22  and infusion ports  30  as well as a modification of the stimulation lead shape to include a bent distal tip having a chosen bend angle. The bend angle helps define the path of travel of the lead within the disc nucleus during emplacement. In other words, imparting a particular bend angle on the distal tip of the stimulation lead causes the stimulation lead to travel in an arcuate path such as shown in  FIG. 1 . Imparting a greater bend angle on the lead results in the stimulation lead traveling in a tighter arcuate path, while imparting a lesser bend angle generally results in the stimulation lead traveling in a broader arc or arcuate path.  
         [0032]     Referring to  FIG. 5 , another embodiment of the stimulation lead is illustrated wherein the lead has a progressively narrowing diameter towards the distal end thereof. With this type of stimulation lead, travel of the lead through the more dense annulus tissue is facilitated because the distal tip has a smaller frontal profile and is more easily controlled.  
         [0033]     Referring to  FIG. 6 , yet another embodiment of the stimulation lead is illustrated wherein the electrodes  22  are not formed circumferentially around the distal portion  20 , but are formed more linearly along one side of the stimulation lead. Additionally, the infusion ports  30  may have more of an oval shape and be larger in size which facilitates greater volumetric infusion. This embodiment may be preferred when it is desired to more precisely direct the array of electrical energy to the target tissue. The electrical energy array that is created by circumferentially arranged electrodes result in transmission patterns having a radial or circular pattern extending away from the stimulation lead. Thus, a plurality of circumferentially arranged electrodes transmit energy in all directions to tissue that surrounds the stimulation lead. On the contrary, locating the electrodes only along one side or edge of the stimulation lead results in transmission of energy in a more linear and less radial pattern, and directed primarily orthogonal or perpendicular to the axis of the stimulation lead. The embodiment of  FIG. 6  also illustrates the distal end as being bent at a desired angle.  
         [0034]      FIG. 7  illustrates yet another embodiment of the stimulation lead wherein the electrodes  22  are concentrated at a particular location, and the infusion ports  30  are spaced in a pattern extending a greater longitudinal length of the lead. A stimulation lead in this particular arrangement may be particularly suitable for repair of a fissure located at a very defined position within the disc, yet if the disc shows great overall degeneration, it is preferable to provide nutrients to a greater length of the annulus whereby the infusion ports  30  can distribute nutrients to a greater length of the annulus.  
         [0035]      FIG. 8  illustrates yet another preferred embodiment of the present invention wherein a stiffening or strengthening member  47  is incorporated within the structural wall of the stimulation lead to provide increased strength to the lead without enlarging the frontal profile of the lead. As shown, the stiffening member  47  is an elongate member that extends longitudinally through the wall of the lead and terminates near the distal end thereof. The stiffening member is malleable to a degree that allows the lead to maintain some desired flexibility during emplacement, but increases the overall shear and torsional strength of the lead to prevent premature failure after emplacement or during removal. The member  47  could be made of a selected metal or thermoplastic approved for medical use.  
         [0036]     Referring to  FIG. 10 , yet another embodiment of the invention is shown wherein an introducer needle  46  is not placed within the disc nucleus, but rather is placed only into the disc annulus, and then the stimulation lead  16  extends through the disc annulus to the target tissue, also shown as a fissure F. In this embodiment, it is preferable that the stimulation lead  16  exits the introducer needle through a bent distal portion  48  so that the lead travels in a more parallel fashion within the annulus and along a more linear path to the target tissue. Accordingly, a stimulation lead having a straight tip like shown in  FIGS. 2, 3  and  5 , would be more suitable according to this embodiment. In the event the distal opening  28  of the lead  16  is of a size which could allow nuclear tissue to clog or block the distal opening  28 , a guide wire  26  may be inserted through the lumen  24  of the lead  16 , and the distal tip  27  of the guide wire could be placed flush with the distal opening  28  in order to prevent clogging of the distal opening  28 , as well as to provide additional rigidity for placement of the stimulation lead  16 . If the guide wire  26  is used, then the guide wire  26  is removed prior to connecting the stimulation lead  16  to an IDP and/or IPG. Also, the central lumen may terminate before passing through the distal tip of the lead. Thus, all of the infusion ports  30  would be arranged on the lead to direct chemicals/nutrients in a perpendicular direction away from the axis of the lead.  
         [0037]      FIGS. 11-13  illustrate yet further embodiments of the present invention wherein the electrodes  22  and infusion ports  30  are dispersed along substantially the entire length of the stimulation lead. In many cases, the disc to be treated has undergone such great degeneration that the entire disc is in need of treatment, as opposed to a more minor degenerative condition such as a single localized fissure. In such cases, it is advantageous to provide both electrical and chemical stimulation to as much of the disc as possible. The embodiments at  FIGS. 11-13  show various combinations of the electrodes  22  and ports  30  that provide greater dispersion of the electrical and chemical stimulation. Specifically, the electrodes are larger and are spread out along a greater length of the lead. The infusion ports are also spread out along a greater length of the lead.  
         [0038]     Based upon the foregoing, the present invention provides a combination electrical and stimulation lead especially adapted for treatment of disc ailments. The various embodiments provide a treating physician with stimulation leads of various configurations, which optimizes a physician&#39;s ability to precisely position the stimulation lead, as well as to precisely direct both electrical and chemical stimulation.  
         [0039]     While the above description and drawings disclose and illustrate embodiments of the present invention, it should be understood that the invention is not limited to these embodiments. Those skilled in the art may make other modifications and changes employing the principles of the present invention, particularly considering the foregoing teachings. Therefore, by the appended claims, the applicant intends to cover such modifications and other embodiments.