Abstract:
An apparatus comprising an electrode subsystem configured to interface to biological tissue, an electronic subsystem electrically coupled to the electrode subsystem by a connector, and a guide tube disposed over at least a portion of the electrode subsystem and the connector. The guide tube includes material to provide stiffness to the electrode subsystem and the connector in an axial direction of the guide tube. The guide tube material is removable from the electrode subsystem and the connector over the electronic subsystem when the electrode subsystem is positioned to interface to the biological tissue and while the electronic subsystem remains electrically coupled to the electrode subsystem.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 12/253,796, filed Oct. 17, 2008, now U.S. Pat. No. 8,224,417,which claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/980,650, filed 17 Oct. 2007, entitled “Guide Tube for an Implantable Device System,” each of which is incorporated in its entirety by this reference, and the priority of each of which is claimed herein. 
     This application is related to U.S. Patent Application Publication No. 2008/0208283, published on Aug. 28, 2008, and entitled “Neural Interface System,” which is incorporated in its entirety by this reference. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to the implantable device field, and more specifically to an improved guide tube of an implantable device. 
     BACKGROUND 
     Conventional microfabricated electrode arrays by themselves are often not mechanically robust enough to be inserted into tissue. Therefore, they must be coupled to a guide tube that is strong enough to maintain a straight trajectory and resist buckling while being inserted into tissue. The electrode arrays are generally coupled to electrical subsystems that are larger than the diameter of the guide tube. Thus, in order to remove a conventional guide tube while maintaining the position of the implanted electrode array, the electrical subsystem must be decoupled from the electrode array and the guide tube is slid off. Decoupling and recoupling the electrical subsystem can be challenging, and any recoupling is potentially exposed to fluids and thus subject to electrical shorting, leading to failure. Thus, there is a need for an improved guide tube that is removable from the implantable device without decoupling the electrical subsystem from the microfabricated electrode arrays. This invention provides such an improved and useful guide tube. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  is a schematic drawing of the system of the first preferred embodiment of the invention. 
         FIG. 1B  is an enlarged view of the area designated  1 B in  FIG. 1A . 
         FIGS. 2-7  are schematic drawings of several variations of the guide tube of the system. 
         FIG. 8  is a schematic drawing of a second preferred embodiment of the invention. 
         FIG.9A  is a schematic drawing of the system implanted in a patient. 
         FIG. 9B  is an enlarged view of the area indicated as  9 B in  FIG. 9A . 
         FIG. 9C  is an enlarged view of the area indicated as  9 C in  FIG. 9A . 
         FIG. 9D  is an enlarged view of the area indicated as  9 D in  FIG. 9A . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of preferred embodiments of the invention is not intended to limit the invention to these embodiments, but rather to enable any person skilled in the art to make and use this invention. 
     As shown in  FIG. 1 , the implantable device system of the preferred embodiments includes a guide tube  10 , a first electrical subsystem  12 , and a second electrical subsystem  14 . The first electrical subsystem  12  is connected to the second electrical subsystem  14 . The guide tube  10  functions to facilitate the insertion of at least one first electrical subsystem  12  into tissue by preventing buckling and maintaining a generally straight trajectory through the tissue, functions to allow the first electrical subsystem(s)  12  to move freely with the tissue (i.e. not being rigidly constrained), and functions to allow the placement of the first electrical subsystem  12  without disconnecting the second electrical subsystem  14 . The implantable device system may be implanted into the brain, spinal cord, peripheral nerve, muscle, or any other suitable anatomical location. The guide tube  10  of the system, however, may be alternatively used in any suitable environment and for any suitable reason. 
     1. The Guide Tube 
     The guide tube  10  of the preferred embodiments functions to facilitate the insertion of at least one first electrical subsystem  12 , functions to allow the first electrical subsystem(s)  12  to move freely with the tissue (i.e. not being rigidly constrained), and functions to allow the placement of the first electrical subsystem  12  without disconnecting the second electrical subsystem  14 . Therefore, the guide tube preferably operates in the following modes: active mode, during which the guide tube is rigid in the axial direction and facilitates insertion of the first electrical subsystem into tissue, and inactive mode, during which the guide tube allows the first electrical subsystem to move freely with the tissue. 
     The guide tube  10  is preferably made of a rigid material, which can be inserted into tissue or other substances without buckling and can maintain a generally straight trajectory through the tissue. The material may be uniformly rigid, or rigid only in a particular direction (such as the axial direction). The material is preferably plastic such as a medical grade plastic, but may alternatively be any suitable material such as metal or a combination of materials. The guide tube  10  may further include a sharpened end adapted to penetrate the tissue and aid in the insertion of the guide tube  10  into the tissue. The guide tube  10  may also include alignment and or fixation features to facilitate positioning and stabilizing the first electrical subsystem  12  in the tissue, particularly during removal of the guide tube. 
     The transition of the guide tube between active mode and inactive mode preferably occurs in one of several variations. In the first two variations, the guide tube  10  is adapted to be removable from the system of electrical subsystems. In another variation, the guide tube  10  is adapted to remain with the system of electrical subsystems. Although the guide tube  10  is preferably adapted in one of the several following variations, the guide tube  10  may be adapted in any suitable fashion or combination thereof to allow the transition of the guide tube between active mode and inactive mode such that the first electrical subsystem  12  to moves freely with the tissue, following the placement of the first electrical subsystem  12 , without disconnecting the second electrical subsystem  14 . 
     1.1 The Guide Tube Removed from a Portion of the System 
     As shown in  FIG. 2 , the guide tube  10  of the first variation defines a slit  18 , which functions to allow the guide tube to be removed over a portion of the system. The slit  18  preferably does not prevent the guide tube  10  from maintaining rigidity as the guide tube  10  is inserted. Preferably a cable connecting the first electrical subsystem  12  and the second electrical subsystem  14  of the implantable device system slides through the slit  18 , but any suitably thin portion of the implantable device system may slide through the slit  18 . The slit preferably is a linear slit  18  or  18 ″, as shown in  FIGs. 2 and 4 , respectively, which runs generally perpendicularly to the end of the guide tube. The slit may alternatively be a spiral slit  18 ′, as shown in  FIG. 3 , and may run at any suitable angle to the end of the guide tube  10 . 
     In a second version, as shown in  FIGS. 4 and 5 , the guide tube  10  may define a plurality of perforation lines  22 , which function to allow the guide tube to be removed over a portion of the system. The perforation lines  22  may supplement or replace the slit  18  of the first variation. As the guide tube  10  is removed over a portion of the system, the portion of the system will apply a generally radial force to the guide tube  10 , which will cause the perforation lines  22  to uncouple, creating an opening or a slit, and allow the guide tube  10  to be removed. There are preferably two axially extending perforation lines  22 , such that the guide tube  10  is uncoupled into two portions. The two portions may be generally equal halves, or one portion may be larger than the other. Alternatively, there may be just one, or may be more than two perforation lines  22  uncoupling the guide tube  10 . Additionally, the perforation lines  22  preferably run a portion of the guide tube  10  (as shown in  FIG. 4 ), but may alternatively run the length of the guide tube  10  (as shown in  FIG. 5 ). The perforation lines  22  are preferably linear and run generally perpendicularly to the end of the guide tube. The perforation lines  22  may alternatively be any suitable geometry and run at any suitable angle to the end of the guide tube  10 . 
     In a third version, the guide tube  10  is made of a brittle material that functions to crack and widen as the guide tube is moved over a portion of the system. The brittle material will not prevent the guide tube  10  from maintaining rigidity as the guide tube  10  is inserted. The material is preferably adapted to crack in response to a force in the radial direction, while allowing the guide tube  10  to maintain rigidity in the axial direction. As the guide tube  10  is moved over a portion of the system, the portion of the system will apply a generally radial force to the guide tube  10 , which will cause the material to crack, creating an opening or a slit, and allow the guide tube  10  to be removed. The guide tube  10  may be entirely made of the brittle material adapted to crack in response to a force in the radial direction and to rigid in the axial direction or a portion of the guide tube may be the brittle material while the remainder is conventional guide tube material. Preferably, the brittle material runs the length of the guide tube  10 , but may alternatively run any suitable portion of the length of the guide tube  10 . The portion of brittle material preferably runs generally perpendicularly to the end of the guide tube, but may alternatively be any suitable geometry and run at any suitable angle to the end of the guide tube  10 . 
     1.2 The Guide Tube Removed Over the Second Electrical Subsystem 
     In a second variation, the guide tube  10  is adapted to break open, or at least expand its diameter to allow the removal of the guide tube  10  over the second electrical subsystem  14 . The guide tube  10  is preferably adapted to break open, or at least expand its diameter in one of several versions. 
     The first three versions are similar to the first three versions of the first variation of the guide tube  10 , as shown in  FIGS. 2-5 , except that the guide tube  10  is made from a material that can be opened or expanded in the radial direction to allow the guide tube  10  to be removed over the second electrical subsystem  14 . 
     In a fourth version, as shown in  FIG. 6 , the guide tube  10  is preferably made of a flexible material that functions to widen as the guide tube is moved over the second electrical subsystem  14  of the system. The flexible material will not prevent the guide tube  10  from maintaining rigidity as the guide tube  10  is inserted. The material is preferably adapted to be flexible in the radial direction, while allowing the guide tube  10  to maintain rigidity in the axial direction. As the guide tube  10  is moved over a portion of the system, the portion of the system will apply a generally radial force to the guide tube  10 , which will cause the material of the guide tube  10  to widen and allow the guide tube  10  to be removed. The guide tube  10  may be entirely made of an anisotropic material adapted to be flexible in the radial direction and rigid in the axial direction. A portion of the guide tube may be the anisotropic material while the remainder is conventional guide tube material, or a portion of the guide tube may be flexible material while the remainder is conventional guide tube material. Preferably, the flexible or partially flexible material runs the length of the guide tube  10 , but may alternatively run any suitable portion of the length of the guide tube  10 . The portion of flexible material preferably runs generally perpendicularly to the end of the guide tube, but may alternatively be any suitable geometry and run at any suitable angle to the end of the guide tube  10 . 
     In a fifth version, as shown in  FIG. 7 , the guide tube  10  includes a flexible material and splines  24  that are rigid in the axial direction, which functions to widen as the guide tube is moved over a portion of the system. The splines  24  will allow the guide tube  10  to maintain rigidity as the guide tube  10  is inserted. As the guide tube  10  is moved over a portion of the system, the portion of the system will apply a generally radial force to the guide tube  10 , which will cause the splines  24  to move apart and the material of the guide tube  10  to flex, widening the diameter of the guide tube  10 , allowing the guide tube  10  to be removed. Alternatively, the guide tube  10  may include the splines  24  alone, and not further include a flexible material or only include the flexible material along a portion of the splines  24 . The splines  24  are preferably strips of any suitable width and thickness and preferably run along the length of the guide tube  10  and run generally perpendicularly to the end of the guide tube. The splines  24  may alternatively be any suitable geometry, run any suitable portion of the length of the guide tube  10 , and run at any suitable angle to the end of the guide tube  10 . The splines  24  are preferably rigid, or may alternatively be flexible in the radial direction and rigid in the axial direction. The splines  24  may alternatively run circumferentially around the guide tube  10  or spiral around the guide tube  10 , such that there are multiple circular splines, or a spring, stacked along the length of the guide tube. The circular splines preferably expand in the radial direction and due to the stacking, would be rigid in the axial direction. 
     1.3 The Guide Tube Adapted to Remain with the Electrical Subsystems 
     The guide tube  10  of the third variation is adapted to remain with the implanted system of electrical subsystems. The guide tube  10  is preferably adapted to be resorbable into the tissue after a period of time. The guide tube  10  in this variation is preferably made from a material that is resorbable such as polyglycolide or polylactide, but may alternatively be made from any suitable bioresorbable material. 
     In a second variation, as shown in  FIG. 7 , the guide tube  10  includes a flexible material and splines  24  that are rigid in the axial direction. The flexible material and splines  24  will not prevent the guide tube  10  from maintaining rigidity as the guide tube  10  is inserted. The splines  24  are preferably strips of any suitable width and thickness and preferably run along the length of the guide tube  10  and run generally perpendicularly to the end of the guide tube. The splines  24  are preferably rigid. The splines  24  may alternatively be any suitable geometry, run any suitable portion of the length of the guide tube  10 , and run at any suitable angle to the end of the guide tube  10 . The splines  24  may alternatively run circumferentially around the guide tube  10  or spiral around the guide tube  10 , such that there are multiple circular splines  24 , or a spring, stacked along the length of the guide tube. In this version, the flexible guide tube  10  may remain implanted, while the splines  24  are removed. 
     2. The Electrical Subsystems 
     The first electrical subsystem  12  of the preferred embodiments functions to interface with the tissue, or any other suitable substance, within which it has been implanted. The first electrical subsystem  12  may include multiple different electrical subsystems or a plurality of the same subsystems. As shown in  FIG. 8 , the first electrical subsystem  12  may include a plurality of electrical subsystems and the guide tube  10  may be adapted to guide multiple first electrical subsystems  12 . The first electrical subsystem  12  is preferably at least one of several versions or any combination thereof. 
     In a first version, the first electrical subsystem  12  is a multi-banded cylindrical electrode with a linear arrangement of four equally spaced cylindrical electrodes, which can be used in monopolar or bipolar modes to deliver electrical stimulation to the surrounding tissue. The electrodes can deliver approximately spherical potential fields from separate locations along the cylindrical carrier. 
     In a second version, as shown in  FIGS. 1 and 8 , the first electrical subsystem  12  is a neural interface electrode array. The electrode array preferably has a plurality of electrode sites, and more preferably a plurality of electrode sites that is more than 4. The neural interface electrode array is adapted to provide dynamic tunable electrical stimulation ranging from stimulation with macroscale specificity to microscale directional patterning. The electrode array is preferably adapted to optimally sample (record) and/or selectively activate (stimulate) neural populations. The plurality of electrode sites can be tuned for recording, stimulation, or any combination thereof. Additionally, at least two electrode sites may be grouped to form a larger composite site that enables tuning the neural interface region for recording and/or stimulation. The neural interface electrode array is preferably made from a thin-film polymer substrate such that there is high density electrode sites at a first end of the array (the distal end) and bonding regions at a second end of the array (the proximal end). The polymer substrate is preferably parylene or some combination of parylene and inorganic dielectrics, but may alternatively be made out of any suitable material. The distal end of the array is preferably coupled to a carrier to provide structural support. The electrode array may further include fluidic channels providing the capability to deliver therapeutic drugs, drugs to inhibit biologic response to the implant, or any other suitable fluid. 
     The first electrical subsystem  12  may be adapted for long term implantation as in the first two variations, or alternatively may be adapted for short-term intraoperative use as in the following third variation. In the third version, the first electrical subsystem  12  is a mapping electrode system, which is adapted to perform clinical deep brain electrophysiological mapping for use in neurosurgerical applications. More specifically, the mapping electrode system is preferably adapted to perform simultaneous multichannel neural recording from precisely known locations along the deep microelectrode track. The mapping electrode may further have extended functionality such as multichannel recording and/or stimulation or fluid delivery. 
     Although the first electrical subsystem  12  is preferably one of these several versions, the first electrical subsystem  12  may be any suitable element or combination of elements to perform the desired functions. 
     The second electrical subsystem  14  of the preferred embodiments functions to operate with the first electrical subsystem  12 . The second electrical subsystem  14  may include multiple different electrical subsystems or a plurality of the same subsystems. Additionally, the guide tube  10  may be adapted to be removable over multiple second electrical subsystems  14 . The second electrical subsystem is preferably at least one of several versions or any combination thereof. 
     In a first version, as shown in  FIG. 3 , the second electrical subsystem  14  is a suitable electronic subsystem to operate with an implantable neural interface. The second electrical subsystem  14  may be a printed circuit board with or without on-board integrated circuits and/or on-chip circuitry for signal conditioning and/or stimulus generation, an Application Specific Integrated Circuit (ASIC), a multiplexer chip, a buffer amplifier, an electronics interface, an implantable pulse generator, an implantable rechargeable battery, integrated electronics for either real-time signal processing of the input (recorded) or output (stimulation) signals, integrated electronics for control of the fluidic components, any other suitable electrical subsystem, or any combination thereof. Although the second electrical subsystem  14  is preferably one of these several subsystems, the second electrical subsystem  14  may be any suitable element or combination of elements to operate any suitable first electrical subsystem  12 . 
     The system may further include a connector such as a cable  16  that functions to couple the first electrical subsystem  12  to the second electrical subsystem  14 . The cable  16  is preferably one of several versions. As shown in  FIGS. 1 and 8 , the cable is preferably a flexible ribbon cable. The ribbon cable is preferably a polymer ribbon cable, but may alternatively be any other suitable ribbon cable. The cable  16  may alternatively be any suitable element to couple the first electrical subsystem  12  to the second electrical subsystem  14 , such as wires, conductive interconnects, etc. The ribbon cable may be encased in silicone or any other suitable material. In some situations, the electrical subsystem may have multiple ribbon cables. Preferably, multiple ribbon cables would be physically attached along their entire length, using a suitable adhesive such as medical grade adhesive or any other suitable connection mechanism. The cable is preferably connected to the electrical subsystems through ball bonds, ball bond, or any other suitable connection mechanisms. The cable  16  may alternatively be seamlessly manufactured with the first and or second electrical subsystem. The cable  16  may further include fluidic channels adapted to deliver therapeutic drugs, drugs to inhibit biologic response to the implant, or any other suitable fluid. 
     As shown in  FIG. 9 , a method of implanting an implant and its corresponding electrical components preferably includes any combination of the following steps (or any other suitable steps): 
     S 110 , which includes attaching a cranial chamber to the skull (preferably in a cranial burr-hole) of a patient ( FIG. 9A ); 
     S 120 , which includes implanting, through the guide tube  10 , a first electrical subsystem  12  which is preferably a mapping electrode system ( FIGS. 9B and 9C );
         removing, through the guide tube  10 , the mapping electrode system following microelectrode recording;       

     S 230 , which includes implanting, through the guide tube  10 , a first electrical subsystem  12  which is preferably a neural interface electrode array coupled via a cable  16  to a second electrical subsystem  14  ( FIGs. 9B and 9C ); 
     S 140 , which includes removing the guide tube from the system ( FIG. 9D ); 
     S 150 , which includes placing the second electrical subsystem  14  within the chamber ( FIG. 9B ); and 
     sealing the electrical subsystems within the chamber. 
     Although omitted for conciseness, the preferred embodiments include every combination and permutation of the various guide tubes  10 , the various expansion elements, the various electrical subsystems, the various cables, and the various methods of use. 
     As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claim.