Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/02—Details
  • A61N1/04—Electrodes
  • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
  • A61N1/0526—Head electrodes
  • A61N1/0529—Electrodes for brain stimulation
  • A61N1/0539—Anchoring of brain electrode systems, e.g. within burr hole
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F11/00—Methods or devices for treatment of the ears or hearing sense; Non-electric hearing aids; Methods or devices for enabling ear patients to achieve auditory perception through physiological senses other than hearing sense; Protective devices for the ears, carried on the body or in the hand
  • A61F11/04—Methods or devices for enabling ear patients to achieve auditory perception through physiological senses other than hearing sense, e.g. through the touch sense
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/02—Details
  • A61N1/04—Electrodes
  • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/02—Details
  • A61N1/04—Electrodes
  • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
  • A61N1/0526—Head electrodes
  • A61N1/0529—Electrodes for brain stimulation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/02—Details
  • A61N1/04—Electrodes
  • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
  • A61N1/0526—Head electrodes
  • A61N1/0529—Electrodes for brain stimulation
  • A61N1/0531—Brain cortex electrodes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/02—Details
  • A61N1/04—Electrodes
  • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
  • A61N1/0526—Head electrodes
  • A61N1/0541—Cochlear electrodes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/18—Applying electric currents by contact electrodes
  • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
  • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
  • A61N1/3605—Implantable neurostimulators for stimulating central or peripheral nerve system
  • A61N1/3606—Implantable neurostimulators for stimulating central or peripheral nerve system adapted for a particular treatment
  • A61N1/361—Phantom sensations, e.g. tinnitus

Definitions

• This invention relates generally to an apparatus and method for treating a hard-of-hearing or deaf patient whose hearing cannot be restored with a cochlear implant, and in particular, to a human cerebral cortex neural prosthetic for delivering electrical signals to the patient's primary auditory cortex.
• This invention also relates generally to an apparatus and method for treating tinnitus, and in particular, to a human cerebral cortex neural prosthetic for delivering geometrically dispersed electrical signals to the patient's primary auditory cortex and/or to a human cerebral cortex or the patient's thala us neural prosthetic for microinfusing geometrically dispersed portions of drugs to the patient's primary auditory cortex or the patient's thalamus.
• the prosthetic can be wireless and can include an electrode with electrical contacts which remain localized with respect to specified neurons or groups of neurons.
• This wireless prosthetic can be used to treat a hard-of-hearing or deaf patient whose hearing cannot be restored with a cochlear implant, and this embodiment of the invention relates, in particular, to a wireless human cerebral cortex neural prosthetic for delivering electrical signals to the patient's primary auditory cortex.
• penetrating electrodes transform what was in the past a two dimensional implant-brain interface ( flat disks on the surface of the brain ) into a three dimensional interface (multiple needle-like electrodes in parallel extending from the surface into the brain substance ) , which vastly increases the device's access to stimulation targets below the surface.
• a two dimensional surface-electrode array may have the potential of generating an image on the "screen” composed of approximately one hundred discreet dots (“pixels”), whereas a three-dimensional array would potentially generate an image with many thousands of dots. The huge potential increase in image resolution would be achieved using a small fraction of the stimulation currents used in the past.
• Penetrating electrodes have the potential to markedly increase both image quality and the safety of the stimulation process.
• Human experimental studies continue at the NIH campus.
• Extramural NIH funding is also directed at supporting engineering research on penetrating electrodes optimally suited for neural prosthetics applications.
• the University of Michigan for example, has made use of computer-chip manufacturing techniques to synthesize tiny electrode arrays.
• the etched electrical contacts on these devices are so small that the distance separating adjacent contacts can be in the range of 50 micrometers, approximately the diameter of two nerve cell bodies.
• Drake, K.L. et al. "Performance of planar multisite microprobes in recording extracellular single-unit intracortical activity," IEEE Trans. BME, 35:719-732, 1988.
• the auditory system is composed of many structural components that are connected extensively by bundles of nerve fibers.
• the system's overall function is to enable humans to extract usable information from sounds in the environment. By transducing acoustic signals into electrical signals that can then be processed in the brain, humans are able to discriminate amongst a wide range of sounds with great precision.
• Figures IA and IB show a side and front view of areas involved in the hearing process.
• the normal transduction of sound waves into electrical signals occurs in cochlea 110, a part of the inner ear located within temporal bone (not shown).
• Cochlea 110 is tonotopically organized, meaning different parts of cochlea 110 respond optimally to different tones; one end of cochlea 110 responds best to high frequency tones, while the other end responds best to low frequency tones.
• Cochlea 110 converts the tones to electrical signals which are then received by cochlea nucleus 116. This converted information is passed from cochlea 110 into brain stem 114 by way of electrical sicfnals carried along the acoustic nerve and in particular, cranial nerve VIII (not shown).
• cochlea nucleus 116 in the brain stem 114.
• the acoustic nerve leaves the temporal bone and enters skull cavity 122, it penetrates brain stem 114 and relays coded signals to cochlear nucleus 116, which is also tonotopically organized.
• cochlear nucleus 116 which is also tonotopically organized.
• sound signals are analyzed at sites throughout brain stem 114 and thalamus 126.
• the final signal analysis site is auditory cortex 150 situated in temporal lobe 156.
• cochlea 110 The mechanisms of function of these various structures has also been extensively studied.
• the function of cochlea 110 is the most well-understood and the function of auditory cortex 150 is the least understood. For example, removal of the cochlea 110 results in complete deafness in ear 160, whereas removal of auditory cortex 150 from one side produces minimal deficits. Despite extensive neural connections with other components of the auditory system, auditory cortex 150 does not appear to be necessary for many auditory functions.
• Cochlear Implant were designed for patients who are deaf as a result of loss of the cochlea's sound transduction mechanism. Implant candidates must have an intact acoustic nerve capable of carrying electrical signals away from the middle ear into the brain stem. The device converts sound waves into electrical signals which are delivered through a multi-contact
• UBS ⁇ TI ⁇ SHEET SSILI 26 stimulating electrode The stimulating electrode is surgically inserted by an otolaryngologist into the d-amaged cochlea. Activation of the contacts stimulates acoustic nerve terminals which would normally be activated by the cochlear sound transduction mechanism. The patient perceives sound as the coded electrical signal is carried from the middle ear into the brain by the acoustic nerve. Cohen, N.L. et al., "A prospective, randomized study of cochlear implants," N. En ⁇ l. J. Med. , 328:233-7, 1993.
• cochlear implants can be remarkably effective in restoring hearing. For example, some previously deaf patients are able to understand conversations over the telephone following insertion of a cochlear implant.
• Cochlear implants are surgically placed in the middle ear which is situated in the temporal bone. In patients who are already deaf, there is very little chance of any additional injury being caused by placement of a cochlear implant; they are very safe device. Because of the low health risk associated with placing cochlear implants, obtaining experimental subjects during the early development stage was not difficult. In this setting design improvements occurred rapidly.
• cochlear nucleus implants there is significantly more risk associated with cochlear nucleus implants than cochlear implants.
• the cochlear nucleus is situated in the brain stem; a very sensitive and vital structure.
• Neurosurgical procedures in the brain stem are among the most difficult and dangerous operations performed. Infiltrating tumors within the substance of the brainstem, for example, are usually considered surgically inoperable. Surgical manipulation or injury of brainstem elements can cause devastating complications, including loss of normal swallowing functions, loss of control of eye movements, paralysis, coma, and death.
• the first cochlear nucleus implant used penetrating electrodes. These functioned well initially, however within two months they had migrated further into the brainstem, causing tingling sensation in the patient's hip as adjacent fiber tracts were inadvertently stimulated. This system was removed and surface electrodes have been used for cochlear nucleus implants since that time. Risks of implanting a cochlear nucleus device are such that patients are only candidates for implantation if they require surgery in that area of the brainstem for some other, usually life threatening reason.
• Treating Deafness Devices designed to treat deafness must take into consideration the underlying cause of deafness. For example, a patient with defective cochlea 110 who still has a functional acoustic nerve, may benefit from an artificial cochlea (cochlear implant). However, if the acoustic nerve is damaged and cannot carry electrical signals, then the problem is "too far downstream" in the signal processing sequence for a cochlear implant to be effective. In that situation, artificial signals must enter the auditory system "beyond the block" either in brain stem 114 or in auditory cortex 150.
• Tinnitus is a disorder where a patient experiences a sound sensation within the head ("a ringing in the ears") in absence of an external stimulus. This uncontrollable ringing can be extremely uncomfortable and often results in severe disability. Tinnitus is a very common disorder affecting an estimated 15% of the U.S. population according to the National Institutes for Health, 1989 National Strategic Research Plan. Hence, approximately 9 million Americans have clinically significant tinnitus with 2 million of those being severely disabled by the disorder.
• O ne approach involves suppression of abnormal neural activity within the auditory nervous system with various anticonvulsant medications.
• anticonvulsant medications include Xylocaine and Lidocaine which are administered intravenously.
• antidepressants, sedatives, biofeedback and counseling methods are also used. None of these methods has been shown to be consistently effective.
• Another widely used approach to treating tinnitus involves "masking" undesirable sound perception by presenting alternative sounds to the patient using an external sound generator.
• an external sound generator is attached to the patient's ear (similar to a hearing aid) and the generator outputs sounds into the patients ear.
• this approach has met with moderate success, it has several significant drawbacks.
• First, such an approach requires that the patient not be deaf in the ear which uses the external sound generator. That is, the external sound generator cannot effectively mask sounds to a deaf ear which subsequently developed tinnitus.
• the external sound generator can be inconvenient to use and can actually result in loss of hearing acuity in healthy ears.
• Another object of the invention is to provide a wireless prosthetic which can be positioned in the brain such that an entire range of tonal frequencies processed by the human brain are accessed thereby.
• Another object of the invention is to provide a wireless prosthetic which allows a physician to physiologically test location and function of neural prosthetic electrodes in patients undergoing surgery for medically intractable epilepsy.
• Another object of the invention to provide a wireless prosthetic apparatus which can be placed in one of a patient's cerebral cortex or in the patient's thalamus to reduce the effects of tinnitus.
• a nother object of the invention is to provide a wireless prosthetic apparatus which can be positioned in the brain such that electric discharges can be accurately delivered to geometrically dispersed locations in either the cortex or thalamus.
• Another object of the invention to provide a prosthetic apparatus which can be placed in one of a patient's cerebral cortex or in the patient's thalamus to reduce the effects of tinnitus.
• Another object of the invention is to provide a prosthetic apparatus which can be positioned in the brain such that electric discharges can be accurately delivered to geometrically dispersed locations in either the cortex or thalamus.
• Another object of the invention is to provide a prosthetic which allows a physician to physiologically test location and function of neural prosthetic electrodes to reduce or eliminate the patient's tinnitus.
• Another object of the invention is to provide a prosthetic apparatus which can be positioned in the brain such that microinfusions of a drug that reduces abnormal neural activity due to tinnitus can be administered in geometrically dispersed locations in the patient's cortex or thalamus.
• Another object of the invention is to provide a prosthetic apparatus which can support a reservoir of the drug so that the microinfusions can be continuously administered.
• Another object of the invention to provide a prosthetic which can be placed in a cerebral cortex to reconstitute sensor input to the brain using microstimulation.
• Another object of the invention is to provide a prosthetic which can be positioned in the brain such that an entire range of tonal frequencies processed by the human brain are accessed thereby.
• Another object of the invention is to provide a prosthetic which allows a physician to physiologically test location and function of neural prosthetic electrodes in patients undergoing surgery for medically intractable epilepsy.
• a nother object of the invention is to provide a wireless prosthetic which allows a physician to physiologically test location and function of neural prosthetic electrodes to reduce or eliminate the patient's tinnitus.
• O ne advantage of the invention is that it does not necessarily require wires to electrically couple the electrode to the stimulator or processor.
• a nother advantage of the invention is that it includes contacts which enable a deaf patient to hear even though the patient's problem is not in his or her cochlear regions but instead is farther "down stream.”
• a nother advantage of the invention is that it can utilize a single electrode.
• a nother advantage of the invention is that it penetrates the brain thus requiring significantly less current to stimulate localized areas of the auditory cortex or thalamus.
• a nother advantage of the invention is that the contacts are sufficiently closely arranged next to each other to provide high resolution stimulation of the auditory cortex.
• a nother advantage of the invention is that it can be used to reduce or eliminate the effects of tinnitus.
• Another advantage of the invention is that the contacts are sufficiently closely arranged next to each other to provide high geometric resolution stimulation of the auditory cortex.
• Another advantage of the invention is that it includes contacts which enable a deaf patient to hear even though the patient's problem is not in his or her cochlear regions but instead is farther "down stream.”
• Another advantage of the invention is that it can utilize a single electrode.
• Another advantage of the invention is that it penetrates the brain thus requiring significantly less current to stimulate localized areas of the auditory cortex.
• Another advantage of the invention is that the contacts are sufficiently closely arranged next to each other to provide high resolution stimulation of the auditory cortex.
• Another advantage of the invention is that it can utilize a single catheter.
• One feature of the invention is that it includes multiple contacts on the longitudinal support.
• Another feature of the invention is that it can includes a speech processor.
• each contact can separately introduce electrical discharges in the primary auditory cortex.
• Another feature of the invention is that it can include a wireless penetrating longitudinal support or electrode.
• Another feature of the invention is that it can include a simulation device. Another feature of the invention is that it includes a penetrating longitudinal support or electrode.
• Another feature of the invention is that it includes multiple contacts on the longitudinal support.
• Another feature of the invention is that it includes a speech processor.
• each contact can separately introduce electrical discharges in the primary auditory cortex.
• Another feature of the invention is that it is arranged along the primary auditory cortex.
• Another feature of the invention is that it can include a flexible wire multicontact electrode.
• Another feature of the invention is that the flexible wire multicontact electrode is inserted into the brain using a rigid introducer.
• a flat plastic plate attached to the longitudinal support helps position the prosthetic in the auditory cortex.
• the flat plastic plate having a cup to receive a sphere coupled to leads which interconnect the contacts to the speech processor.
• Another feature of the invention is that it includes a penetrating longitudinal support or electrode.
• Another feature of the invention is that it utilizes a catheter to administer micro-infusions of the drugs to disperse locations in the patient's cortex or thalamus.
• the catheter includes an electrode for recording discharges in the patient's cortex or thalamus.
• Another feature of the invention is that it utiliz.es a drug reservoir for containing reserve portions of the drug.
• a wireless neural prosthetic device for a brain target zone of a patient, for receiving processed electrical signals from an exterior device, including: an electrode arranged in the brain target zone having a plurality of electrical contacts; and circuitry electrically coupled to the plurality of electrical contacts for receiving the processed electrical signals and selectively outputting electrical discharges to the plurality of electrical contacts in accordance with the processed electrical signals.
• a method of inserting the wireless neural prosthetic device including the steps of: attaching a stereotaxic introducer probe onto the attachment end; inserting the electrode into the brain target zone; inputting one of a gas, a liquid and a malleable solid material into the attachment end of the electrode; and detaching the probe from the attachment end of the electrode.
• a wireless neural prosthetic system for a targeted brain zone of a patient including: a processor for outputting processed electrical signals; an electrode arranged in the targeted brain zone having a plurality
• a neural prosthetic device for a primary auditory cortex of a patient including: a speech processor for receiving and processing audio information and for outputting processed electrical signals, a support arranged in the primary auditory cortex having a plurality of electrical contacts, the support being arranged in the primary auditory cortex and each of the plurality of electrical contacts independently outputting electrical discharges in accordance with the processed electrical signals; and electrical coupling means for electrically coupling the electrical contacts to the speech processor.
• the neural prosthetic apparatus as above, wherein the support is arranged in the primary auditory cortex and the plurality of electrical contacts are arranged such that the plurality of electrical contacts approximately tonotopically match the primary auditory cortex.
• a method of implanting the above support including the steps of: acquiring a 3 dimensional digital image of the patient's brain and storing the 3 dimensional digital image in a memory of a computer; digitally subtracting data from the 3 dimensional digital image to yield a modified 3 dimensional digital image which shows the orientation of the primary auditory cortex in the patient's brain; and inserting the support into the primary auditory cortex using the modified 3 dimensional digital image as a guide.
• Figures IA and IB show the orientation of a patient's primary auditory cortex in relation to the patients cochlea and cochlear nucleus.
• Figure 2 shows a human cerebral cortex neural prosthetic according to one embodiment of the invention.
• Figure 3A shows a side view of a plane A which intersects a coronal section with a Sylvian fissure exposed
• Figures 3B and 3C show the coronal section before and after tissue is digitally "peeled off" the Sylvian fissure.
• Figure 4 shows a neural prosthetic with a support having electrical contacts and it's speech processor.
• Figure 5 shows a prosthetic which includes two longitudinal supports according to another embodiment of the invention.
• Figure 6 shows a prosthetic according to yet another embodiment of the invention.
• Figure 7A shows the prosthetic of Figure 6 as looking down on the patients brain surface
• Figure 7B shows a closer view of a stopping piece with a cup and a lid
• Figure 7C corresponds to Figure 7A with the support inserted.
• Figures 8A and 8B show the orientation of a patient's primary auditory cortex in relation to the patients cochlea and cochlear nucleus.
• Figure 9A shows a multi-contact recording/stimulating electrode system 100' for blocking and/or masking the abnormal electrical activity present in tinnitus patients according to one embodiment of the invention.
• Figure 9B shows a human cerebral cortex neural prosthetic according to one embodiment of the invention.
• Figure 10A shows a side view of a plane A which intersects a coronal section with a Sylvian fissure exposed
• Figures 10B and IOC show the coronal section before and after tissue is digitally "peeled off" the Sylvian fissure.
• Figure 11 shows a neural prosthetic with a support having electrical contacts and it's stimulation device.
• Figure 12 shows a prosthetic which includes two longitudinal supports according to another embodiment of the invention.
• Figure 13 shows a prosthetic according to yet another embodiment of the invention.
• Figure 14A shows the prosthetic of Figure 13 as looking down on the patients brain surface
• Figure 14B shows a closer view of a stopping piece with a cup and a lid
• Figure 14C corresponds to Figure 14A with the support inserted.
• Figure 15 shows another embodiment of the invention involving drug-infusion into regionally targeted locations within the brain according to another embodiment of the invention.
• Figure 16 shows a closer view of catheter with ports or openings.
• Figures 17A and 17B show the orientation of a patient's primary auditory cortex in relation to the patients cochlea and cochlear nucleus.
• Figure 18A shows a wireless human cerebral cortex neural prosthetic system according to one embodiment of the invention.
• Figure 18B shows a wireless human cerebral cortex neural prosthetic electrode (support) according to one embodiment of the invention.
• Figure 18C shows a closeup of the transmission and receiving electronics in the electrode.
• Figure 18D shows a schematic block diagram of microchip circuitry contained in the wireless prosthetic support.
• Figure 19A shows a side view of a plane A which intersects a coronal section with a Sylvian fissure exposed, and Figures 19B and 19C show the coronal section before and after tissue is digitally "peeled off" the Sylvian fissure.
• Figure 20A shows a multi-contact wireless recording/stimulating electrode system 100" for blocking the abnormal electrical activity present in tinnitus patients according to one embodiment of the invention.
• Figure 20B shows a wireless human cerebral cortex neural prosthetic according to that embodiment of the invention.
• Figure 20C shows a closeup of the transmission and receiving electronics in the electrode.
• Figure 21 shows the steps involved in implanting the wireless electrodes (or supports).
• Figure 22 shows a prosthetic which includes two longitudinal supports for either the a human cerebral cortex neural prosthetic system a multi-contact recording/stimulating electrode system.
• Advanced imaging combined with an intraoperative stereotactic system now enable placement of penetrating electrodes into auditory cortex during routine epilepsy surgery without dissection of the Sylvian fissure.
• Primary auditory cortex 150 in Figures IA and IB is tonotopically organized, meaning stimulation in different areas is likely to cause the patient to perceive different tones. These tones form the building blocks of complex sound phenomena such as speech. Tonotopic organization is a fundamental characteristic of the cochlea and cochlear nucleus as well, as discussed above. Auditory cortex 150, however, has its tonotopic map stretched across a larger volume of tissue (greater that twice the volume of cochlear nucleus 116). Greater tissue volume enables placement of a greater number of electrical contacts for a given tonotopic zone. This results in increased signal resolution and improved clarity of auditory sensation. Finally, because of anatomical differences, auditory cortex 150 can accommodate penetrating electrode arrays which cannot be safely placed into the cochlear nucleus.
• Figure 2 shows a human cerebral cortex neural prosthetic 200 according to one embodiment of the invention.
• Prosthetic 200 has a first end 206a and a second end 206b which is blunt or smoothly curved.
• Prosthetic 200 has electrical contacts 220 along a longitudinal support 226.
• Support 226 can be anywhere from several millimeters long to several centimeters long.
• Electrical contacts 220 are small metal pads which can be separately electrically charged via respective wires 232 available at first end 206a.
• Wires 232 have leads 238 which are coupled to a speech processor (not shown).
• Electrical contacts 220 are spaced approximately 10 micrometers to several millimeters apart and preferably approximately 50 to 150 micrometers apart.
• Longitudinal support 226 can be a rigid support or a flexible wire with a rigid introducer which enables the physician to introduce prosthetic 200 into a patient's brain and then subsequently remove the rigid introducer thereby exposing electrical contacts 220 to auditory cortex 150.
• Support 226 can be one of the probes shown in Figures 3-5 in "Possible Multichannel Recording and Stimulating Electrode Arrays: A Catalog of Available Designs" by the Center for Integrated Sensors and Circuits, University of Michigan Ann Arbor, Michigan, the contents of which are incorporated herein by reference.
• Electrodes such as Depthalon Depth Electrodes and interconnection cables from PMT Corporation 1500 Park Road, Chanhassen, MN, 55317 could also be used as support 226 and electrical couplers between contacts 220 and a speech processor (410 in Figure 4) .
• Electrical contacts 220 must operate as high impedance (megohms) contacts as opposed to low impedance (a few ohms to several thousand ohms) contacts as some of the electrodes. This enables the contacts to output a small (a few microamperes as apposed to a few milliamperes) current. This also localizes the potentials applied to the patient's primary auditory cortex to approximately a few hundred micrometers. The localization of applied electric charges corresponds to the tonotopic spacing of nerve cell pairs.
• Prosthetic 200 is arranged along a longitudinal direction of auditory cortex 150.
• auditory cortex 150 is located in the transverse temporal gyro and is buried deep within the Sylvian fissure. Consequently, its location cannot be determined simply by looking at an exposed surface of the brain. Therefore, MRI imaging techniques must be employed to reveal the exact orientation of auditory cortex 150.
• Figure 3A shows a side view of a plane A which intersects a coronal section 310 as well as a view of coronal section 310 with Sylvian fissure 316 exposed.
• Figures 3B and 3C show coronal section 310 before and after tissue is digitally "peeled off" to expose auditory cortex 150.
• One or more resulting mounds 320 is revealed in Figure 3C and this mound corresponds to auditory cortex 150 of Figure 17B. Mound 320 does not appear until after tissue on the underside of Sylvian fissure 316 is reconstructed to provide the 3-D image.
• Figure 4 shows prosthetic 200 just prior to insertion into auditory cortex 150.
• Figure 4 shows a speech processor 410 coupled to leads 238 via coupling cable 414. Examples of speech processors for speech processor 410 is Nucleus Device made by Cochlear Corporation. Speech processor 410 can be miniaturized and placed directly above ear 416 in the patient's mastoid.
• Figure 4 also shows additional diagnostic equipment including an oscilloscope 420 coupled to prosthetic 200 via cable 424.
• Figure 5 shows a prosthetic 510 which includes two longitudinal supports 226a and 226b according to another embodiment of the invention. Although two supports are shown, three or more such supports could be used. Longitudinal support 226a has wires 232a with corresponding leads 238a and longitudinal support 226b has wires 232b and leads 238b. Leads 238a and 238b are again connected to speech processor 410 as in Figure 4. In addition, scope 420 can be used to observe signals output to longitudinal support 226a and 226b.
• Figure 6 shows a prosthetic 610 according; to yet another embodiment of the invention.
• Figure 6 shows longitudinal support rod 226 with first end 606a- and second end 606b.
• End 606a is arranged in the region of auditory cortex 150 with low tones (or high tomes as previously discussed) and second end 606b is arranged in the region of auditory cortex 150 with high ( or low) tones in a manner similar to first end 206a and second end 206b of Figure 2.
• longitudinal support 226 has a sphere 616 which is stopped by a stopping piece 614. This enable the physician to insert longitudinal support 226 at a wide range of angles and yet secure prosthetic 610 once longitudinal support 226 has been inserted.
• Figure 7A shows prosthetic 610 of Figure 6 as looking down on the patients brain surface 704.
• Figure 7B shows a closer view of stopping piece 614 with a cup 708 and a lid 714 with a notch 716 for passing leads 232.
• Figure 7C corresponds to Figure 7A with support 226 inserted into surface 704 and sphere 616 resting in cup 708.
• Figure 7C also shows lid 716 covering sphere 616 with leads 232 extending out of notch 716.
• auditory cortex 150 is situated in temporal lobe 156, neurosurgeons expose this portion of the brain routinely during a wide range of operations.
• the auditory region is not surrounded by vital structures. If a patient is diagnosed with an infiltrating tumor of the non-dominant auditory cortex, for example, the neurosurgeon can resect this tissue with very little risk of complicatio .
• the primary auditory region of the human brain is buried deep within the sylvian fissure. It is not visible from the brain surface and its exact location varies slightly from one person to the next. MRI and CT scanners were not invented at the time of Dr. Dobelle's experiments so the anatomy of the patients' auditory cortex could not be studied prior to surgery, and this region could only be visualized with difficulty in the operating room after the Sylvian fissure was surgically dissected. Once the buried auditory cortex was exposed, surface stimulating electrodes were placed by hand over the area thought to be auditory cortex and the brain was stimulated in a fashion similar to that used to generate visual phosphenes.
• the auditory system is composed of many structural components that are connected extensively by bundles of nerve fibers.
• the system's overall function is to enable humans to extract usable information from sounds in the environment. By transducing acoustic signals into electrical signals that can then be processed in the brain, humans are able to discriminate amongst a wide range of sounds with great precision.
• FIGS 8A and 8B show a side and front view of areas involved in the hearing process.
• the normal transduction of sound waves into electrical signals occurs in cochlea 110', a part of the inner ear located within temporal bone (not shown).
• Cochlea 110' is tonotopically organized, meaning different parts of cochlea 110' respond optimally to different tones; one end of cochlea 110' responds best to high frequency tones, while the other end responds best to low frequency tones.
• Cochlea 110' converts the tones to electrical signals which are then received by cochlea nucleus 116'. This converted information is passed from cochlea 110' into brain stem 114' by way of electrical signals carried along the acoustic nerve and in particular, cranial nerve VIII (not shown).
• the next important auditory structure encountered is cochlea nucleus 116' in the brain stem 114'.
• the acoustic nerve leaves the temporal bone and enters skull cavity 122' , it penetrates brain stem 114' and relays coded signals to cochlear nucleus 116', which is also tonotopically organized.
• sound signa l s are analyzed at sites throughout brain stem 114' and thalamus 12 6 ' .
• the final signal analysis site is auditory cortex 15 0 ' situated in temporal lobe 156'.
• cochlea 110' The functions of cochlea 110' is the most well-understood and the function of auditory cortex 150' is the least understood. For example, removal of the cochlea 11 0 ' results in complete deafness in ear 160', whereas removal of au d itory cortex 150' from one side produces minimal deficits. Despite extensive neural connections with other components of the auditory system, auditory cortex 150' does not appear to be necessary for many auditory functions.
• Ad vanced imaging combined with an intraoperative stereotactic system now enable placement of penetrating electro d es into auditory cortex during routine epilepsy surgery without dissection of the Sylvian fissure.
• Primary auditory cortex 150' in Figures 8A and 8B is tonotopically organized, meaning stimulation in different areas is likely to cause the patient to perceive different tones. These tones form the building blocks of complex sound phenomena such as speech. Tonotopic organization is a fundamental characteristic of the cochlea and cochlear nucleus as well, as discussed above. Auditory cortex 150', however, has its tonotopic map stretched across a larger volume of tissue (greater that twice the volume of cochlear nucleus 116'). Greater tissue volume enables placement of a greater number of electrical contacts for a given tonotopic zone. This results in increased signal resolution and improved clarity of auditory sensation. Finally, because of anatomical differences, auditory cortex 150' can accommodate penetrating electrode arrays.
• Figure 9A shows a multi-contact recording/stimulating electrode system 100' for blocking and/or masking the abnormal electrical activity present in tinnitus patients according to one embodiment of the invention.
• system 100' includes a multi-contact stimulating/recording electrode 104' connected to cables 108' via connector 112'. Cables 108' enter skull 116a' at burr hole opening 120' of skull 116a' and are connected to a stimulation device 410' positioned in subcutaneous tissue of axial skeleton (thorax or abdomen) .
• FIG. 9B shows a closer view of multi-contact stimulating/recording electrode 104' of electrode system 100'.
• Electrode 104' has a first end 206a' and a second end 206b' which is blunt or smoothly curved.
• Electrode 104' has electrical contacts 220' along a longitudinal support 226'. Support 226' can be anywhere from several millimeters long to several centimeters long.
• Electrical contacts 220' are small metal pads which can be separately electrically charged via respective wires 232' available at first end 206a'. Wires 232' are coupled to stimulation device 410' (see Figures 9A and 11). Electrical contacts 220' are spaced approximately 10 micrometers to several millimeters apart and preferably approximately 50 to 150 micrometers apart.
• Electrode 104' is stereotaxically placed into the primary auditory cortex of the patient with tinnitus. This can be done using a standard stereotaxic head frame under local anesthesia. That is, the above discussed three dimensional computerized MRI reconstruction method of Figures 10A-10C is used to stereotaxically place electrode 104' within the targeted region of auditory cortex 150'. Correct placement is confirmed by presenting a series of tones to the patient and mapping the tonotopic responses of the neurons along electrode 104'.
• mapping procedure In deaf patients, this mapping procedure is not possible, but mapping can still be carried out using microstimulation currents delivered to various contacts along electrode 104'.
• the deaf patient describes the relative pitch of the sounds he or she perceives following stimulation, whereby the electrically stimulated location and parameters which most closely match the patient's tinnitus are determined.
• This approach could be used in the thalamus (MGN) as well, but the preferred embodiment involves implantation in the cortex. Regardless of whether or not stimulating electrode 104' is placed into the correct region of the cortex or into the correct region of the MGN, electrode 104' is coupled to stimulation device 410' via cables 108' and in particular, wires 232a'.
• Longitudinal support 226' can be a rigid support or a flexible wire with a rigid introducer which enables the physician to introduce electrode 104' into a patient's brain and then subsequently remove the rigid introducer thereby exposing electrical contacts 220' to auditory cortex 150'.
• Support 226' can be one of the probes shown in Figures 3-5 in "Possible Multichannel Recording and Stimulating Electrode Arrays: A Catalog of Available Designs" by the Center for Integrated Sensors and Circuits, University of Michigan Ann Arbor, Michigan, the contents, of which are incorporated herein by reference.
• Electrodes such as Depthalon Depth Electrodes and interconnection cables from PMT Corporation 1500 Park Road, Chanhassen, MN, 55317 could also be used as support 226' and electrical couplers between contacts 220' and a speech processor (410' in Figure 11) .
• Electrical contacts 220' can operate as high impedance (megohms) contacts or low impedance (a few ohms to several thousand ohms) contacts as some of the electrodes. This enables the contacts to output a small (a few microamperes as apposed to a few milliamperes) current.
• High impedance contacts localize the potentials applied to the patient's primary auditory cortex to approximately a few hundred micrometers. The localization of applied electric charges corresponds to the tonotopic spacing of nerve cell pairs.
• Electrode 104' is arranged along a longitudinal direction of auditory cortex 150'.
• auditory cortex 150' is located in the transverse temporal gyrus and is buried deep within the Sylvian fissure. Consequently, its location cannot be determined simply by looking at an exposed surface of the brain. Therefore, MRI imaging techniques must be employed to reveal the exact orientation of auditory cortex 150'.
• SUBSTITUTE SHEET (RULE 26 A single coronal image of an individual's brain cannot reveal the exact orientation of auditory cortex 150'. However, for treatment of tinnitus, a standard coronal MRI provides a fairly good estimate as to the location of the target region, whether or not the target region is the auditory cortex or the thalamus. However, if more precise targeting is desired, a series of two dimensional images must be obtained and a resulting 3-D MRI image constructed. Once such an image is constructed, the digital data making up that image can be transformed to provide a view of the Sylvian fissure. This in turn exposes auditory cortex 150' as a mole-like mound.
• tissue on top of the digital image can be "peeled off” to expose the sylvian fissure and consequently auditory cortex 150' "pops out” of the image.
• This process is described in "Three-dimensional In Vivo Mapping of Brain Lesions in Humans", by Hanna Damasio, MD, Randall Frank, the contents of which are incorporated herein by reference.
• Figure 10A shows a side view of a plane A which intersects a coronal section 310' as well as a view of coronal section 310' with Sylvian fissure 316' exposed.
• Figures 10B and 10C show coronal section 310' before and after tissue is digitally "peeled off" to expose auditory cortex 150'.
• One or more resulting mounds 320' is revealed in Figure 10C and this mound corresponds to auditory cortex 150' of Figure 8B.
• Mound 320' does not appear until after tissue on the underside of Sylvian fissure 316' is reconstructed to provide the 3-D image.
• Figure 11 shows electrode 104' just prior to insertion into auditory cortex 150'.
• stimulation device 410' coupled to wires 232' via cable 108'.
• Stimulation device 410' is a chronic electrical stimulation device. This stimulator device is well tested and widely available. Examples include chronic epidural simulators made by Medtronics used for chronic back and leg pain and deep brain stimulators, as well as nearly all types of cochlear implants.
• the above electrical implantation technique for tinnitus is quick and safe, e.g., over 100 auditory cortex region electrode implantations have been performed in patients being evaluated for medically intractable seizures as reported by a French epilepsy surgery group.
• electrode 104' is placed in the exact site of presumed abnormal neuronal electrical activity, it is much more effective in disrupting or altering abnormal neuronal electrical activity, thereby eliminating tinnitus.
• preliminary testing has shown that placement of electrode 104' within the central auditory system causes patients to perceive sounds, and this will likely be the case even in patients who are deaf from causes refractory to cochlear implantation.
• stimulation in the auditory cortex does not impair hearing in tinnitus patients who do have good hearing.
• Figure 12 shows an electrode 510' which includes two longitudinal supports 226a' and 226b' according to another embodiment of the invention. Although two supports are shown, three or more such supports could be used. Longitudinal support 226a' is connected to cable 108a' containing wires 232a' via connector 112a' and longitudinal support 226b' is connected to cable 108b' containing wires 232b' via connector 112b'. Cables 108a' and 108b' are again connected to stimulation device 410' as in Figure 11.
• Figure 13 shows a electrode 610' according to yet another embodiment of the invention.
• Figure 13 shows longitudinal support rod 226' with first end 606a' and second end 606b'.
• End 606a' is arranged in the region of auditory cortex 150' with low tones (or high tones as previously discussed) and second end 606b' is arranged in the region of auditory cortex 150' with high (or low) tones in a manner similar to first end 206a' and second end 206b' of Figure 9B.
• longitudinal support 226' has a sphere 616' which is stopped by a stopping piece 614'. This enable the physician to insert longitudinal support 226' at a wide range of angles and yet secure electrode 610' once longitudinal support 226' has been inserted.
• Figure 14A shows electrode 610' of Figure 13 as looking down on the patients brain surface 704'.
• Figure 14B shows a closer view of stopping piece 614' with a cup 708' and a lid 714' with a notch 716' for passing leads 232'.
• Figure 14C corresponds to Figure 14A with support 226' inserted into surface 704' and sphere 616' resting in cup 708'.
• Figure 14C also shows lid 716' covering sphere 616' with leads 232' extending out of notch 716'.
• Figure 15 shows another embodiment of the invention involving drug-infusion into regionally targeted locations within the brain.
• the alternative drug-infusion treatment strategy relies on the same principal of regionally targeted treatment within the brain, but employs a different effector to eliminate the abnormal neural activity causing tinnitus.
• a small drug infusion catheter 801 is stereotaxically placed into either the auditory cortex or thalamus (MGN) and microinfusions of various drugs that block abnormal neural activity are infused into the targeted locations.
• MGN thalamus
• a drug infusion catheter-recording device 800' is connected to an injectable (rechargeable) drug reservoir-pump 804' via connector 803' which is secured with sutures widely used in neurosurgery.
• Pump 804' is secured to the patient's skull 808' under the scalp and is not exposed to the external environment.
• Pump 804' has a valve 824' which can be accessed externally so that additional drugs can be injected via a syringe (not shown) without reopening the patient's scalp.
• Catheter 801' has multiple ports 814' from which the drugs are microinfused into the targeted brain regions.
• FIG 16 shows a closer view of catheter 801' with ports or openings 814'.
• Catheter can be made, for example, of silastic such as the catheters sold by Radionics, Codman, and Medtronics.
• Catheter 801' need not have a circular cross-section 817 and instead can be flat, elliptical or any other shape which facilitates broader diffusion of the drug.
• Catheter 801' can include a small embedded recording-stimulating electrode 819' which can be connected to stimulation device 410' so that it can be properly positioned. Electrophysiologic recording data from this special catheter electrode will provide physiologic confirmation of proper catheter position in auditory cortex.
• 9JBSTITUTE SHEET(RULE 26) diameters of ports (or openings) 814' can be approximately between 10 micrometers and several millimeters and preferably between approximately 40 micrometers and 1 millimeter.
• the centers of ports 814' can also be tens of micrometers apart to millimeters apart and the spacing need not be uniform.
• the precise amount of drug infusion depends on the type of drug but can be determined at the outset of implantation.
• catheter 801' is initially inserted into the targeted location in the manner described above. The patient is then asked if there is any noticeable reduction in ringing due to the tinnitus as the amount of drug infusion is manually adjusted. The amount of infusion is that amount which is required to eliminate the ringing. Once the amount is determined, the appropriate chronic infusion pump 804' is connected to catheter 801' and all incisions are closed. Post-operative modifications of infusion rates can be carried out using percutaneous radio control techniques, e.g., Medtronics.
• the alternative drug-infusion treatment strategy relies on the same electrode placement principals as described above with respect to Figures 10A-10C. Namely, a series of images must again be obtained and a resulting 3-D MRI image constructed. Once the image is constructed, the digital data making up that image can be transformed to provide a view of the Sylvian fissure. This in turn exposes auditory cortex 150' as a mole-like mound. Again, tissue on top of the digital image can be "peeled off” to expose the sylvian fissure and consequently auditory cortex 150' "pops out” of the image.
• Advanced imaging combined with an intraoperative stereotactic system now enable placement of penetrating electrodes into auditory cortex during routine epilepsy surgery without dissection of the Sylvian fissure.
• Primary auditory cortex 150 in Figures 17A and 17B is tonotopically organized, meaning stimulation in different areas is likely to cause the patient to perceive different tones. These tones form the building blocks of complex sound phenomena such as speech. Tonotopic organization is a fundamental characteristic of the cochlea and cochlear nucleus as well, as discussed above. Auditory cortex 150", however, has its tonotopic map stretched across a larger volume of tissue (greater that twice the volume of cochlear nucleus 116"). Greater tissue volume enables placement of a greater number of electrical contacts for a given tonotopic zone. This results in increased signal resolution and improved clarity of auditory sensation. Finally, because of anatomical differences, auditory cortex 150" can accommodate penetrating electrode arrays which cannot be safely placed into the cochlear nucleus.
• Figure 18A shows a wireless human cerebral cortex neural prosthetic 200" according to one embodiment of the invention.
• Figures 18B and 18C show closer views of prosthetic 200" and a portion of prosthetic 200" containing microchip circuitry 211" which transmits and receives signals to and from a speech processor 410" via a transmitter/receiver unit 404".
• Transmitter/receiver unit 404" need not be mechanically secured to processor 410", it only needs to be electrically connected via wires (not shown) to processor 410".
• Transmitter/receiver unit 404" acts as a transmitter and receiver of the electromagnetic waves will be discussed below.
• Prosthetic 200" has a first end 206a" and a second end 206b" which is blunt or smoothly curved.
• Prosthetic 200" has electrical contacts 220" along a longitudinal support 226".
• Support 226" can be anywhere from several millimeters long to several centimeters long.
• Electrical contacts 220" are small metal pads which can be separately electrically charged via respective wires 232" which couple contacts 220" to microchip circuitry 211".
• Electrical contacts 220" are spaced approximately 10 micrometers to several millimeters apart and preferably approximately 50 to 150 micrometers apart.
• Speech processor 410 outputs magnetic or electromagnetic signals (referred to here as processor signals) via
• unit 404" acts as a transmitter, transmitting the processor signals and circuitry 211" acts as a receiver, receiving, and demodulating/decoding the processor signals to determine which contacts to charge.
• contacts 220" can act as conductive sensors, sensing the presence of electrical discharges.
• circuitry 211" electrically coupled to contacts 220" via wires 232" acts as a transmitter, transmitting neuron activity (neuron discharge) signals which provide information as to the time and location of neuron discharges, and unit 404" acts as a receiver, receiving and demodulating/decoding these neuron activity signals.
• the Intrel II system by Medtronics is one example of a wireless system which can transmit and receive signals between a processor and a multi-programmable neurological pulse generator which can be modified (see discussion below) and used as processor 410" and unit 404".
• the pulse generator would be modified into the shape of prosthetic 200" with electrical contacts 220" (not limited to the number of contacts in the Intrel II system) and be lighter and smaller than that of the pulse generator of Intrel II.
• the processor of Intrel II allows control of the amplitude, duration, repetition rates, etc..., of stimulating signals (referred to as pulses).
• FIG 18C shows microchip circuitry 211" embedded in prosthetic 200".
• Microchip circuitry 211" shown can include a transmitting/receiving antenna 255" which transmits the above discussed neuron discharge signals to transmitter/receiver 404" as well as receives the above discussed processor signals.
• Microchip circuitry can be near first end 206a" but could be imbedded near second end 206b" as well. However, it is preferable to have circuitry 211" near first end 206", because the latter is nearest skull 116"—thereby provided a better coupling between it and transmitter/receiver 404".
• Figure 18D shows a schematic block diagram of circuitry 211".
• Figure 18D shows antenna 255" electrically coupled to processor signal modulator/demodulator 265" which in turn is electrically coupled to processor 275".
• Antenna 255" receives processor signals which can be modulated on an electromagnetic wave carrier which can pass through a patient's skull with little to no damage to the patient.
• the frequency of the electro-magnetic wave carrier can be any frequency which provides the best link between transmitter/receiver 404".
• Antenna 255" transmits the electromagnetic waves to modulator/demodulator 265" which demodulates these waves and in turn outputs intermediate processor signals to processor 275".
• Processor 275" can include an analog-to-digital converter 267" which receives and digitizes the intermediate processor signals to yield digital information. Processor 275” processes this digital information and outputs resulting processed information to driver/receiver 277" which is coupled to contacts 222" via wires 232". Driver/receiver 277” in turn stimulates the contacts 220" in accordance with the processed information.
• Support 226 can be an active (having on-chip electronics 211") version of any one of the probes shown in Figures 3-5 in "Possible Multichannel Recording and Stimulating Electrode Arrays: A Catalog of Available Designs" by the Center for Integrated Sensors and Circuits, University of Michigan Ann Arbor, Michigan, the contents of which are incorporated herein by reference.
• the on-chip electronics alternative electrodes such as Depthalon Depth Electrodes and interconnection cables from PMT Corporation 1500 Park Road, Chanhassen, MN, 55317 could also be used as support or electrode 226".
• Another such on chip version is the above discussed Itrel II systems discussed above.
• Electrical contacts 220" must operate as high impedance (megohms) contacts or low impedance (a few ohms to several thousand ohms) contacts as some of the electrodes.
• High impedance contacts enable the contacts to output a small (a few microamperes as apposed to a few milliamperes) current, which helps localize the potentials applied to the patient's primary auditory cortex to approximately a few hundred micrometers. The localization of applied electric charges corresponds to the tonotopic spacing of nerve cell pairs.
• Prosthetic 200" is arranged along a longitudinal direction of auditory cortex 150".
• auditory cortex 150" is located in the transverse temporal gyro and is buried deep within the Sylvian fissure. Consequently, its location cannot be determined simply by looking at an exposed surface of the brain. Therefore, MRI imaging techniques must be employed to reveal the exact orientation of auditory cortex 150".
• Figure 19A shows a side view of a plane A which intersects a coronal section 310" as well as a view of coronal section 310" with Sylvian fissure 316" exposed.
• Figures 19B and 19C show coronal section 310a" before and after tissue is digitally “peeled off” to expose auditory cortex 150".
• One or more resulting mounds 320" is revealed in Figure 19C and this mound corresponds to auditory cortex 150" of Figure 17B. Mound 320" does not appear until after tissue on the underside of Sylvian fissure 316" is reconstructed to provide the 3-D image.
• auditory cortex 150 is situated in temporal lobe 156"
• neurosurgeons expose this portion of the brain routinely during a wide range of operations.
• the auditory region is not surrounded by vital structures. If a patient is diagnosed with an infiltrating tumor of the non-dominant auditory cortex, for example, the neurosurgeon can resect this tissue with very little risk of complication.
• Electrode 104" is stereotaxically placed into the primary auditory cortex of the patient with tinnitus. This can be done using a standard stereotaxic head frame under local anesthesia. That is, the above discussed three dimensional computerized MRI reconstruction method of Figures 19A-19C is used to stereotaxically place electrode 104" within the targeted region of auditory cortex 150". Correct placement is confirmed by presenting a series of tones to the patient and mapping the tonotopic responses of the neurons along electrode 104".
• mapping procedure In deaf patients, this mapping procedure is not possible, but mapping can still be carried out using microstimulation currents delivered to various contacts along electrode 104".
• the deaf patient describes the relative pitch of the sounds he or she perceives following stimulation, whereby the electrically stimulated location and parameters which most closely match the patient's tinnitus are determined.
• This approach could be used in the thalamus (MGN) as well, but the preferred embodiment involves implantation in the cortex. Regardless of whether or not stimulating electrode 104" is placed into the correct region of the cortex or into the correct region of the MGN, electrode 104" is coupled to stimulation device 410" via cables 108" and in particular, wires 232a".
• Longitudinal support 226" can be a rigid support or a flexible wire with a rigid introducer which enables the physician to introduce electrode 104" into a patient's brain and then subsequently remove the rigid introducer thereby exposing electrical contacts 220" to auditory cortex 150".
• Support 226" can be one of the probes shown in Figures 3-5 in "Possible Multichannel Recording and Stimulating Electrode Arrays: A Catalog of Available Designs" by the Center for Integrated Sensors and Circuits, University of Michigan Ann Arbor, Michigan, the contents of which are incorporated herein by reference.
• Electrodes such as Depthalon Depth Electrodes and interconnection cables from PMT Corporation 1500 Park Road, Chanhassen, MN, 55317 could also be used as support 226" and electrical couplers between contacts 220" and a speech processor (410" in Figure 20A) .
• Electrical contacts 220" must operate as high impedance (megohms) contacts as opposed to low impedance (a few ohms to several thousand ohms) contacts as some of the electrodes. This enables the contacts to output a small (a few microamperes as apposed to a few milliamperes) current. This also localizes the potentials applied to the patient's primary auditory cortex to approximately a few hundred micrometers. The localization of applied electric charges corresponds to the tonotopic spacing of nerve cell pairs.
• Electrode 104" is arranged along a longitudinal direction of auditory cortex 150".
• auditory cortex 150" is located in the transverse temporal gyro and is buried deep within the Sylvian fissure. Consequently, its location cannot be determined simply by looking at an exposed surface of the brain. Therefore, MRI imaging techniques must be employed to reveal the exact orientation of auditory cortex 150".
• Figure 19A shows a side view of a plane A which intersects a coronal section 310" as well as a view of coronal section 310" with Sylvian fissure 316" exposed.
• Figures 19B and 19C show coronal section 310" before and after tissue is digitally “peeled off” to expose auditory cortex 150".
• One or more resulting mounds 320" is revealed in Figure 19C and this mound corresponds to auditory cortex 150" of Figure 17B. Mound 320" does not
• Figure 20A shows a multi-contact recording/stimulating electrode system 100" for blocking and/or masking the abnormal electrical activity present in tinnitus patients according to one embodiment of the invention.
• system 100" includes a multi-contact stimulating/recording electrode 104" connected to cables 108" via connector 112". Cables 108" enter skull 116" at burr hole opening 120" of skull 116" and are connected to a stimulation device 410" positioned in subcutaneous tissue of axial skeleton (thorax or abdomen).
• FIG 20B shows a closer view of multi-contact stimulating/recording electrode 104" of electrode system 100.
• Electrode 104" has a first end 206a" and a second end 206b" which is blunt or smoothly curved.
• Electrode 104" has electrical contacts 220" along a longitudinal support 226". Support 226" can be anywhere from several millimeters long to several centimeters long.
• Electrical contacts 220" are small metal pads which can be separately electrically charged via respective wires 232" available at first end 206a”. Wires 232" are coupled to stimulation device 410" (see Figure 20A) .
• Electrical contacts 220" are spaced approximately 10 micrometers to several millimeters apart and preferably approximately 50 to 150 micrometers apart.
• Electrode 104" is stereotaxically placed into the primary auditory cortex of the patient with tinnitus. This can be done using a standard stereotaxic head frame under local anesthesia. Alternatively, the above discussed three dimensional computerized MRI reconstruction method of Figures 19A-19C can be used to stereotaxically place electrode 104" within the targeted region of auditory cortex 150". Correct placement is confirmed by presenting a series of tones to the patient and mapping the tonotopic responses of the neurons along electrode 104".
• mapping In deaf patients, this mapping procedure is not possible, but mapping can still be carried out using microstimulation currents delivered to various contacts along electrode 104".
• the deaf patient describes the relative pitch of the sounds he or she perceives following stimulation, whereby the electrically stimulated location and parameters which most closely match the patient's tinnitus are determined.
• This approach could be used in the thalamus (MGN) as well, but the preferred embodiment involves implantation in the cortex. Regardless of whether or not stimulating electrode 104" is placed into the correct region of the cortex or into the correct region of the MGN, electrode
• SUfcSTITUTE SHEET (RULE 26) 104" is coupled to stimulation device 410" via cables 108" and in particular, wires 232a".
• Stimulation device 410 can be a chronic electrical stimulation device. This stimulator device is well tested and widely available. Examples include chronic epidural simulators made by Medtronics used for chronic back and leg pain, as well as nearly all types of cochlear implants.
• FIG 21 shows how support 226" or electrode 104" are implanted into the patient's brain target zone 503" (auditory cortex or thalamus).
• brain target zone 503" is determined using stereotaxic techniques as discussed above with respect to Figures 19A-19C.
• step 1 involves attaching a stereotaxic introducer probe 507" onto attachment end 517" which has a female coupler valve 521" (see also Figures 18B and 20B).
• Probe 507" is a standard stereotaxic introducer probe.
• the step 1 of attaching probe 507" onto attachment end 517 involves inserting an insertion tip 525" into female coupler valve 521" contained within a deflated or unexpanded brain anchor 122".
• Brain anchor 122" can be rubber, plastic, or any material which does not cause the patient any adverse complications.
• Step 2 then involves inserting support 226" or electrode 104" into brain target zone 503".
• Step 3 involves inflating brain anchor 122" by inputting a gas, liquid or malleable solid material 535" into a back end 531" of probe 507".
• step 4 involves detaching probe 507" from attachment end 517" of support 226" or electrode 104" and filling burr hole 120".
• SUBST/TUTE SHEET (KJL ⁇ ⁇ 26) however, the doctor may conduct a series of questions, as discussed above, of the patient and intermittently adjusting the orientation of support 22.6" or electrode 104" for the optimal effect. These questions are different depending on whether support 226" is being inserted into target zone 503" of hard-of- hearing patient or electrode 104" is being inserted into target zone 503" of a tinnitus patient.
• the former questioning process is conducted in a manner described above with respect to support 226".
• the latter questioning process was described above and the latter questioning involves repeatedly adjusting the position of electrode 104" using probe 507" and asking the patient if the effects of the tinnitus is improved or worsened, until the optimal orientation is determined.
• the above implantation technique for the neural prosthetic for hearing and for tinnitus is quick and safe, e.g., over 100 auditory cortex region electrode implantations have been performed in patients being evaluated for medically intractable seizures.
• electrode 104" since electrode 104" is placed in the exact site of presumed abnormal neuronal electrical activity, it is extremely effective in disrupting or altering abnormal neuronal electrical activity, thereby eliminating tinnitus.
• preliminary testing has shown that placement of electrode 104" within the central auditory system causes patients to perceive sounds and this will be the case for patients who are deaf from causes refractory to cochlear implantation.
• stimulation in the auditory cortex does not impair hearing in tinnitus patients who do have good hearing.
• FIG 22 shows an electrode system 510" which includes two longitudinal supports (electrodes) 226a" and 226b", according to another embodiment of the invention.
• supports can correspond to support 200" in Figure 18A or to multi-contact stimulating and recording electrode 104" in Figure 20A depending or whether system 510" is for a hard of hearing patient or a tinnitus patient, respectively—reference numbers corresponding to the latter will be included in parenthetically below. Although two supports are shown, three or more such supports could be used.
• Longitudinal support 226a" is coupled via transmitter/receiver 404" (404'" for a tinnitus patient) to speech processor 410" (stimulation device 410'") in the same manner that support 200" (multi-contact electrode 104") was coupled to speech processor 410" (stimulation device 410'"), namely via a transmitter/receiver link 404" (404'").

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• 1995
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