Abstract:
One embodiment includes a tubular housing for electrically connecting an implantable stimulation device to an implantable electrical stimulation lead. The tubular housing includes a tubular outer segment including a first material, a tubular middle segment inside the outer segment in contact with the outer segment including a second material, and a tubular inner segment inside the middle segment in contact with the middle segment including a third material. A circumferential groove in the inner segment exposes a portion of the middle segment to an axial hole through the tubular housing. The groove is adapted to receive a coiled spring. The groove enables transmission of stimulation pulses from the exposed portion of the middle segment, through the coiled spring, to the stimulation lead inserted through the axial hole for stimulation of tissue in a patient.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/721,878 filed Sep. 29, 2005, entitled “HOUSING PROVIDING AN ELECTRICAL STIMULATION LEAD CONTACT IN AN IMPLANTABLE NEUROSTIMULATION DEVICE,” which is incorporated herein by reference. 

   TECHNICAL FIELD 
   This application relates generally to implantable neurostimulation devices and more particularly to a housing providing an electrical stimulation lead contact in an implantable neurostimulation device. 
   BACKGROUND 
   An implantable neurostimulation device includes a housing for receiving a proximal end of an implantable electrical stimulation lead and electrically connecting the circuitry of the device to appropriate components of the stimulation lead to enable stimulation of tissue in a patient. The housing includes electrical contacts corresponding to terminal electrodes located along the proximal end of the stimulation lead. The terminal electrodes are connected to corresponding stimulation electrodes located along the distal end of the stimulation lead via wires running through the stimulation lead. Electrical stimulation pulses are generated at the device and transmitted through the electrical contacts, terminal electrodes, wires, and stimulation electrodes to the tissue to be stimulated. A typical electrical contact for such a device is made of platinum or an alloy of approximately 90% platinum and approximately 10% iridium. Platinum is expensive, but resistant to oxidation and corrosion that may adversely affect electrical connectivity between the electrical contact and the corresponding terminal electrode of the stimulation lead. 
   SUMMARY 
   According to some embodiments, disadvantages and problems associated with previous structures for providing electrical connectivity between an implantable neurostimulation device and an implantable electrical stimulation lead may be reduced or eliminated. 
   One embodiment includes a tubular housing for electrically connecting an implantable neurostimulation device to an implantable electrical stimulation lead. The tubular housing includes a tubular outer segment including a first material, a tubular middle segment inside the outer segment in contact with the outer segment including a second material, and a tubular inner segment inside the middle segment in contact with the middle segment including a third material. A circumferential groove in the inner segment exposes a portion of the middle segment to an axial hole through the tubular housing. The groove is adapted to receive a coiled spring. The groove enables transmission of stimulation pulses from the exposed portion of the middle segment, through the coiled spring, to the stimulation lead inserted through the axial hole for neurostimulation of tissue in a patient. 
   Particular embodiments of the present invention may provide one or more technical advantages. For example, particular embodiments may reduce an amount of platinum needed for an electrical contact of the neurostimulation device while retaining one or more benefits of using platinum (such as resistance to oxidation and corrosion) for the electrical contact. Certain embodiments of the present invention may provide all, some, or none of these technical 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 herein. 
   The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     To provide an understanding of some embodiments and features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  illustrates an example implantable neurostimulation device; 
       FIG. 2  illustrates an example header assembly of the example implantable neurostimulation device; 
       FIG. 3  illustrates an example housing for an electrical contact in the example implantable neurostimulation device; 
       FIG. 4  illustrates a before-tooling cross-section of the example housing; 
       FIG. 5  illustrates an after-tooling cross-section of the example housing; 
       FIG. 6  illustrates a cross-section of the example housing including an example coiled spring; 
       FIGS. 7A and 7B  illustrate example implantable neurostimulation systems; and 
       FIG. 8  illustrates an example method for reducing an amount of a contact material for an electrical stimulation lead contact in an implantable neurostimulation device. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates an example implantable neurostimulation device  10 . In particular embodiments, implantable device  10  is an implantable pulse generator (IPG) including a power source (such as a battery) and electronics (such as hardware, software, or embedded logic components) for generating electrical stimulation pulses for transmission to nerve fibers or other anatomic structures in a patient for neurostimulation. Possible applications of implantable device  10  include treating chronic pain, treating neurological disorders, and treating motor dysfunctions. Although a particular implantable device  10  is illustrated and described, representative embodiments contemplate any suitable implantable device  10 . As an example and not by way of limitation, in particular embodiments, implantable device  10  is an implantable receiver of a radio frequency (RF) neurostimulation system that, when implanted, receives power and electrical stimulation pulses from an transmitter located outside the body of the patient. 
     FIG. 2  illustrates an example header assembly  12  of implantable device  10 . In particular embodiments, header assembly  12  includes electrical contacts corresponding to terminal electrodes located along the proximal end of a stimulation lead. The terminal electrodes are connected to corresponding stimulation electrodes located along the distal end of the stimulation lead via wires running through the stimulation lead. Electrical stimulation pulses are generated at implantable device  10  and transmitted through the electrical contacts, terminal electrodes, wires, and stimulation electrodes to the tissue to be stimulated. The stimulation electrodes deliver the stimulation pulses to nerve fibers or other anatomic structures according to placement of the stimulation electrodes within the body of the patient. As an example and not by way of limitation, in particular embodiments, the stimulation electrodes are placed to deliver the stimulation pulses to a portion of the spinal cord of the patient to treat chronic pain. Although header assembly  12  is illustrated as accommodating two stimulation leads each having eight stimulation electrodes, representative embodiments contemplate header assembly  12  accommodating any suitable number of stimulation leads (e.g., a single stimulation lead) each having any suitable number of stimulation electrodes (e.g., sixteen stimulation electrodes). For ease of understanding, a single stimulation lead is described unless otherwise indicated. 
   In particular embodiments, header assembly  12  receives a stimulation lead through an opening  14  and one or more housings  16  inside header assembly  12 . A connector block  18  and a screw  20  inside header assembly  12  anchor the stimulation lead to header assembly  12 . In particular embodiments, where stimulation lead includes eight terminal electrodes, header assembly  12  receives the stimulation lead through seven housings  16  and one connector block  18 , as illustrated in  FIG. 2 . In a particular embodiment, connector block  18  is used to connect to the most proximal terminal electrode in a manner that more fully secures the stimulation lead to prevent the stimulation lead from separating from header assembly  12  while implanted in the patient. Although connector block  18  is illustrated and described, representative embodiments contemplate connector block  18  being omitted and a housing  16  to connect to each terminal electrode including the most distal terminal electrode. Plugs  22  cover housings  16  and connector blocks  18  and help hold housings  16  and connector blocks  18  in place inside header assembly  12 . Housings  16  each provide electrical contact allowing stimulation pulses to travel from implantable device  10  through housings  16  to the terminal electrodes of the stimulation lead, as described below. To reduce an occurrence of oxidation, corrosion, or both on housing  16  adversely affecting electrical contact at housing  16 , one or more portions of housing  16  may be made of platinum, an alloy of platinum, or another material resistant to oxidation and corrosion, as described below. Because such material is relatively expensive, housing  16  is a relatively expensive component of implantable device  10 . To reduce material costs associated with housing  16  while retaining one or more benefits of using platinum, an alloy of platinum, or another relatively expensive material, such as resistance to oxidation and corrosion, according to representative embodiments only a portion of housing  16  is made of platinum, an alloy of platinum, or another relatively expensive material, as described below. 
     FIG. 3  illustrates an example housing  16 . In particular embodiments, housing  16  is a tube including an inner tubular portion  24 , a middle tubular portion  26 , and an outer tubular portion  28 . In particular embodiments, housing  16  is constructed according to a cladding process well-known in the metal fabrication art. An inside of housing  16  defines a hole  30 . Housing  16  receives a stimulation lead though hole  30 . Plane  32  intersects housing  16 . 
   In particular embodiments, inner tubular portion  24  and outer tubular portion  28  are made of stainless steel or a multiphase alloy of Nickel, Cobalt, Chromium, and Molybdenum (such as MP35N alloy). Inner tubular portion  24  and outer tubular portion  28  may be made of the same or different materials. Middle tubular portion  26  is made of platinum, an alloy of approximately 90% Platinum and approximately 10% iridium, or another material that is expensive relative to the material or materials that form inner tubular portion  24  and outer tubular portion  28 . In contrast to previous housings  16  made entirely of platinum or a platinum alloy, in particular embodiments only middle tubular portion  26  of housing  16  contains the platinum, platinum alloy, or other relatively expensive material. As a result, material costs associated with housing  16  are less than if all or some of inner tubular portion  24 , outer tubular portion  28 , or both also contained platinum, a platinum alloy, or another relatively expensive material. 
   To achieve some but not all of the material cost benefits described above, outer tubular portion  24  may be made of stainless steel or another relatively inexpensive material and both middle tubular portion  26  and inner tubular portion  28  may be made of platinum, a platinum alloy, or another relatively expensive material. Similarly, to achieve some but not all of the material cost benefits described above, inner tubular portion  28  may be made of stainless steel or another relatively inexpensive material and both middle tubular portion  26  and outer tubular portion  24  may be made of platinum, a platinum alloy, or another relatively expensive material. Although a particular housing  16  including particular inner, middle, and outer tubular portions  24 ,  26 , and  28 , respectively, made of particular materials is illustrated and described, representative embodiments contemplate any suitable housing  16  including any suitable inner, middle, and outer tubular portions  24 ,  26 , and  28 , respectively, made of any suitable materials, provided one or more portions considered less critical for electrical contact are made of a material or materials that is inexpensive relative to a material or materials forming one or more portions considered more critical for electrical contact. 
     FIG. 4  illustrates a before-tooling cross-section of housing  16  through plane  32 , and  FIG. 5  illustrates an after-tooling cross-section of housing  16  through plane  32 . Before tooling, middle tubular portion  26  of housing  16  is unexposed to hole  30 . After tooling, groove  34  exposes middle tubular portion  26  of housing  16  to hole  30  to allow electrical contact between middle tubular portion  26  of housing  16  and a conductive object placed in groove  34  and therefore to allow stimulation pulses to travel from middle tubular portion  26  of housing  16  to a stimulation lead running through hole  30 , as described below. In particular embodiments, a screw machine tools housing  16  to create groove  34  according to a screw machine process well-known in the metal tooling art. In addition, after tooling, edges on housing  16  may, but need not, be chamfered (or rounded), as illustrated in  FIG. 5 . 
     FIG. 6  illustrates a cross-section, through plane  32 , of housing  16  with an example coiled spring  34  lying in groove  34 . In particular embodiments, coiled spring  34  is a canted, coiled spring  34 . When housing  16  receives a stimulation lead though hole  30 , coiled spring  34  is compressed between the stimulation lead and middle tubular portion  26  of housing  16  to secure the stimulation lead in housing  16  and to secure coiled spring  34  in groove  34 . Coiled spring  34  transmits stimulation pulses from middle tubular portion  26  of housing  16  to the stimulation lead. Because in particular embodiments at least middle tubular portion  26  is made of platinum or an alloy of approximately 90% platinum and approximately 10% iridium, oxidation and corrosion are unlikely to impede electrical contact between housing  16  and coiled spring  34 . Moreover, because in particular embodiments only a tubular portion of housing (e.g., only middle tubular portion  26 ) contains platinum, a platinum alloy, or another relatively expensive material, material costs associated housing  16  are less than if all or some of inner tubular portion  24 , outer tubular portion  28 , or both also contained such material. 
     FIGS. 7A and 7B  illustrate example implantable neurostimulation systems  38 . Stimulation system  38  generates and applies a stimulus to a target area of the brain, the spinal cord, or a peripheral or other nerve. For example, a target area may be an area of the brain located in the cortex or, as a more particular example, in the primary auditory cortex to treat tinnitus. In general terms, stimulation system  38  includes an implantable neurostimulation device  12  and an implantable electrical stimulation lead  40  for applying the electrical stimulation pulses to target nerve tissue. In operation, both of these primary components are implanted in the person&#39;s body. Implantable neurostimulation device  12  is coupled to a connecting portion  42  of stimulation lead  40 . Implantable neurostimulation device  12  controls the electrical stimulation pulses transmitted to electrodes  44  located on a stimulating portion  46  of stimulation lead  40 , which is positioned on, in, near, or otherwise proximate the target nerve tissue, according to suitable stimulation parameters (e.g., duration, amplitude or intensity information, frequency information, etc.). A doctor, the patient, or another user of implantable neurostimulation device  12  may directly or indirectly input stimulation parameters to specify or modify the electrical stimulation provided. 
   Known neurostimulation devices can be adapted by utilizing a header assembly according to representative embodiments. In one embodiment, as shown in  FIG. 7A , implantable neurostimulation device  12  includes an IPG. An example of a known IPG may be one manufactured by Advanced Neuromodulation Systems, Inc., such as the Genesis® System, part numbers 3604, 3608, 3609, and 3644. In another embodiment, as shown in  FIG. 1B , implantable neurostimulation device  12  includes an implantable wireless receiver. An example of a known wireless receiver may be one manufactured by Advanced Neuromodulation Systems, Inc., such as the Renew® System, part numbers 3408 and 3416. The wireless receiver is capable of receiving wireless signals from a wireless transmitter  48  located external to the person&#39;s body. The wireless signals are represented in  FIG. 1B  by wireless link symbol  50 . A doctor, the patient, or another user of implantable neurostimulation device  12  may use a controller  52  located external to the person&#39;s body to provide control signals for operation of implantable neurostimulation device  12 . Controller  52  provides the control signals to wireless transmitter  48 , wireless transmitter  48  transmits the control signals and power to the wireless receiver of implantable neurostimulation device  12 , and implantable neurostimulation device  12  uses the control signals to vary the stimulation parameters of electrical stimulation pulses transmitted through stimulation lead  40  to the stimulation site. An example wireless transmitter  48  may be one manufactured by Advanced Neuromodulation Systems, Inc., such as the Renew® System, part numbers 3508 and 3516. 
     FIG. 8  illustrates an example method for reducing an amount of a contact material for an electrical stimulation lead contact in an implantable neurostimulation device. The method begins at step  100 , where a middle tubular portion  26  of platinum, an alloy of approximately 90% platinum and approximately 10% iridium, or another relatively expensive material is clad with an inner tubular portion  24  and an outer tubular portion  28  of stainless steel, MP35N alloy, or another relatively inexpensive material to construct a housing  16 . At step  102 , a groove  34  is tooled into inner tubular portion  24  to expose middle tubular portion  26 . At step  104 , a coiled spring  34  is placed into groove  34 . At step  106 , housing  16  is placed into an implantable device  10 . At step  108 , before or during implantation of implantable device  10  into the body of a patient, a stimulation lead is inserted into housing  16  to electrically connect implantable device  10  to the stimulation lead, at which point the method ends. More specifically, in particular embodiments, housing  16  is electrically connected through coiled spring  34  to a corresponding terminal electrode of the stimulation lead, which is connected to a corresponding stimulation electrode of the stimulation lead via a corresponding wire running through the stimulation lead. 
   Although representative embodiments have been discussed in terms of neurostimulation devices, representative embodiments may provide a header assembly for any suitable stimulation device. For example, representative embodiments may provide a header assembly for spinal cord stimulation systems, deep brain stimulation systems, cortical stimulation systems, peripheral nerve stimulation systems, gastric pacing stimulation systems, functional stimulation systems, cardiac pacing stimulation systems, cardiac defibrillation systems, etc. 
   Although certain representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate when reading the present application, other processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the described embodiments may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.