Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-08-13
2001-09-25
Jastrzab, Jeffrey R. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06295472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an apparatus and method for providing stochastic independent neural stimulation, and in particular, a neural stimulation system and method for initiating pseudospontaneous activity in the auditory nerve, which can be used to treat tinnitus.
2. Background of the Related Art
Fundamental differences currently exist between electrical stimulation and acoustic stimulation of the auditory nerve. Electrical stimulation of the auditory nerve, for example, via a cochlear implant, generally results in more cross-fiber synchrony, less within fiber jitter, and less dynamic range, as compared with acoustic stimulation which occurs in individuals having normal hearing.
FIG. 1
shows the magnitude of a related art pattern of electrically-evoked compound action potentials (EAPs) from an auditory nerve of a human subject with an electrical stimulus of 1 kHz (1016 pulses/s). The EAP magnitudes are normalized to the magnitude of the first EAP in the record.
FIG. 1
shows the typical alternating pattern previously described in the art. This pattern arises because of the refractory period of the nerve and can degrade the neural representation of the stimulus envelope. With a first stimulus
102
a large response occurs, likely because of synchronous activation of a large number of fibers. These fibers are subsequently refractory driving a second pulse
104
, and accordingly a small response is generated. By the time of a third pulse
106
, an increased pool of fibers becomes available (non-refractory) and the corresponding response increases. The alternating synchronized response pattern can be caused by a lack or decrease of spontaneous activity in the auditory nerve and can continue indefinitely.
Loss of spontaneous activity in the auditory nerve is one proposed mechanism for tinnitus. Proposed biological mechanisms for the loss of spontaneous activity in the auditory nerve include loss of hair cells in the cochlea. In addition, the loss of hair cells over time is a proposed mechanism for the loss of auditory neurons likely caused by related activities at synapses connecting the hair cells to the auditory neurons in the cochlea.
Tinnitus is a disorder where a patient experiences a sound sensation within the head (“a ringing in the ears”) in the absence of an external stimulus. This uncontrollable ringing can be extremely uncomfortable and often results in severe disability. Restoration of spontaneous activity may potentially improve tinnitus suppression. 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 Plan. Hence, approximately 9 million Americans have clinically significant tinnitus with 2 million of those being severely disabled by the disorder.
Methods and apparatus that generate stochastically independent or “pseudospontaneous” neural activity in the auditory nerve have been modeled and tested with discernable improvements in auditory capabilities including reductions in tinnitis. See U.S. patent application Ser. No. 09/023,279 filed on Feb. 13, 1998, entitled “Speech Processing System and Method Using Pseudospontaneous Stimulation,” which is hereby incorporated by reference. However, biological and somatosensory responses to gradual or rapid reversals of the loss of spontaneous activity in the auditory nerve, for example, were heretofore unknown. Preferably, pseudospontaneous neural activity would be introduced without perception to a patient. For example, in an auditory nerve the desired treatments of tinnitus associated with sensorineural hearing loss would suppress the tinnitus without producing any additional sensations and auditory percepts.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and method of neural stimulation that substantially reduces or obviates at least one of the problems caused by disadvantages of the related art.
Another object of the present invention is to provide an apparatus and method that imperceptibly generates stochastically independent or “pseudospontaneous” neural activity.
Yet another object of the present invention is to provide an apparatus and method that imperceptibly generates statistically independent or “pseudospontaneous” activity in an auditory nerve to suppress tinnitus.
Still yet another object of the present invention is to provide an inner ear or middle ear auditory prosthesis that suppresses tinnitus without producing additional sensations.
A further object of the present invention is to provide an apparatus and method that determines and imperceptibly achieves electrical stimulation to increase stochastic independence of a plurality of nerve fibers.
A still further object of the present invention is to provide an apparatus and method that delivers an undetected high frequency signal to generate desired activity in a nerve.
A still further object of the present invention is to provide an apparatus and method that increases hearing capabilities by providing a prescribed signal to auditory neurons.
To achieve at least the above objects in a whole or in parts, there is provided a method and apparatus according to the present invention for generating pseudospontaneous activity in a nerve that includes generating an electrical signal, modifying the electrical signal to a sustained effective level while the electrical signal remains substantially physiologically imperceptible to the patient, and applying the electrical signal to the auditory nerve to generate pseudospontaneous activity in the auditory nerve.
To further achieve at least the above objects in a whole or in parts, there is provided a neural prosthetic apparatus for treatment of a patient with tinnitus, including a pseudospontaneous signal generator that generates an electrical signal, an adaptor coupled to the generator that modifies the electrical signal to a sustained effective level while the electrical signal remains substantially physiologically imperceptible to the patient, an arrangement of at least one electrical contact adapted to be affixed nearby the cochlea of the patient, a stimulation device coupled to the adaptor that applies the electrical signal to the at least one electrical contact, the electrical signal capable of generating pseudospontaneous activity in the auditory nerve, and wherein the neural prosthetic apparatus effectively alleviates the tinnitus of the patient.
To further achieve at least the above objects in a whole or in parts, there is provided a neural prosthetic apparatus for treatment of a patient with tinnitus, including an adaptor circuit coupled to the stimulation device that modifies one or more electrical signals that include transitions between first and second amplitudes occurring at a frequency greater than approximately 2 kHz to a sustained effective level while the electrical signal remains substantially physiologically imperceptible to the patient, an arrangement of at least one electrical contact adapted to be affixed within the cochlea of the patient, and electrical coupling means for electrically coupling the at least one electrical contact to the stimulation device, and wherein the neural prosthetic apparatus effectively alleviates the tinnitus of the patient.
To further achieve at least the above objects in a whole or in parts, there is provided a method of making a neural prosthetic apparatus, including generating a pseudospontaneous electrical signal, determining the parameters for ramping the pseudospontaneous electrical signal from a first voltage level to a second voltage level, wherein the pseudospontaneous electrical signal applied to an auditory nerve of a patient at the second voltage level effectively generates pseudospontaneous activity in the auditory nerve, and wherein the parameters maintain the pseudospontaneous electrical signal at an approximate level below which pain is perceived by the patient.
To further achieve at least the above objects in a whole or in parts, there is provided a
Abbas Paul J.
Brown Carolyn J.
Rubinstein Jay T.
Tyler Richard S.
Fleshner & Kim LLP
Jastrzab Jeffrey R.
The University of Iowa Research Foundation
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