Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-09-11
2004-02-10
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06690974
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to an implantable neurostimulator having improved efficacy in treating epilepsy and other neurological disorders, and particularly in reducing the incidence of epileptic seizures, and also to processes of using that neurostimulator.
BACKGROUND OF THE INVENTION
Epileptic seizures are characterized by excessive or abnormally synchronous neuronal activity. Neurologists recognize a wide variety of seizures. Partial onset seizures begin in one part of the brain; general onset seizures arise throughout the entire brain simultaneously. When partial onset seizures progress to involve much of the brain, they are said to have “secondarily generalized.” Some seizures result in the loss of conscious awareness and are termed “complex” seizures. So-called “simple” seizures may involve other symptoms, but consciousness is unimpaired. Seizure symptoms may include sensory distortions, involuntary movements, or loss of muscle tone. The behavioral features of a seizure will often reflect a function of the cortex where the abnormal electrical activity is found.
Physicians have been able to treat epilepsy by resecting certain brain areas by surgery and by medication. Brain surgery is irreversible, and is ineffective or is associated with neural morbidity in a sizable percentage of cases. Medication is the most prevalent treatment for epilepsy. It is effective in over half of patients, but in the reminder of the patients, the medication is either ineffective in controlling seizures, or the patients suffer from debilitating side effects. A more promising method of treating patients having epileptic seizures is by electrical stimulation of the brain.
Since the early 1970's, electrical brain stimulators have been used to provide more or less constant stimulation, the stimulation largely being unrelated to detected electrical activity.
Electrical stimulation of the nervous system has been used to suppress seizures. A device is described in Cooper et al. for stimulation of the cerebellum. See, “The Effect of Chronic Stimulation of Cerebellar Cortex on Epilepsy and Man,” I. S. Cooper et al. in
The Cerebellum, Epilepsy and Behavior
, Cooper, Riklan and Snyder eds., Plenum Press, New York, 1974. Others have utilized devices that stimulate the centromedian nucleus of the thalamus. See, “Electrical Stimulation of the Centromedian Thalamic Nucleus in Control of Seizures: Long Term Studies,” F. Velasco et al,
Epilepsia
, 36 (1): 63-71, 1995. Chaos Theory has been used to apply stimulation to a seizure focus in vitro to abort the seizure. See S. Schiff et al, “Controlling Chaos in the Brain,”
Nature,
370: 615-620, Aug. 25, 1994.
Non responsive electrical stimulation devices have been used for significant periods. The devices and procedures did not constitute a panacea, however. For instance, a seventeen-year follow-up study shown in Davis et al. (“Cerebellar Stimulation for Seizure Control 17 Year Study,” Proceedings of the Meeting of the American Society for Stereotactic and Functional Neurosurgery, Pittsburgh, Pa., Jun. 16-19, 1991 and in
Stereotact. Funct. Neurosurg.
1992; 58: 200-208) showed that less than one-half of the patients became seizure free, even though 85% showed some benefit.
In contrast, responsive stimulation, specifically electrical stimulation that is applied to the brain, has not yet been used to treat patients in long-term studies. This is true even though there are algorithms suitable for detection of the onset of an epileptic seizure. For instance, Qu et al. provide an algorithm said to recognize patterns of electrical activity similar to those developed while recording an actual epileptic seizure. See, Qu et al., “A Seizure Warning System for Long-Term Epilepsy Monitoring,”
Neurology
1995; 45: 2250-2254. Similarly, Osorio, et al. have suggested an algorithm applied to signals from intracranial electrodes with good results. See Osorio et al., “A Method For Accurate Automated Real-Time Seizure Detection,”
Epilepsia
1995, 36(supp. 4).
None of the cited documents describes procedures in which a non-responsive electrical stimulation signal is applied to the brain in a first mode and, upon detection of impending or of extant epileptiform electrical activity, a second responsive mode of stimulation is applied to the brain either with or without cessation of non-responsive stimulation.
SUMMARY OF THE INVENTION
The neurostimulator disclosed herein itself generally involves two modes of electrical stimulation: the first involves delivering a non-responsive electrical stimulation signal which is applied to the central nervous system to reduce the likelihood of a seizure or other undesirable neurological even from occurring, and a second mode that involves delivering electrical stimulation signal or signals when epileptiform waveforms are impending or extant.
The responsive electrical stimulation signal or signals are intended to terminate epileptiform activity, e.g., to desynchronize abnormally synchronous brain electrical activity.
Alternatively, the second mode may be used to deliver sensory stimulation, e.g., a scalp or sound stimulation, to the patient rather than deliver electrical stimulation to the patient.
Finally, the neurostimulator may be used by a physician to induce epileptiform activity and then verify the effectiveness of the parameters of the neurostimulation signals.
The invention is an implantable neurostimulator having improved efficacy in treating epilepsy and other neurological disorders and processes of using that neurostimulator. The method generally includes three or more steps. Initially, a non-responsive electrical stimulation signal is applied to the brain in a non-responsive mode. Secondly, some brain electrical activity is detected either during the non-responsive stimulation signal or after the non-responsive stimulation signal is paused. Third, when that detected electrical activity shows impending or existing epileptiform brain electrical activity, a second electrical stimulation signal is applied to the brain. Alternatively, a sensory stimulation, e.g., sound or scalp twitch, may be directed to the patient in place of or in addition to the second electrical stimulation signal.
The first or non-responsive electrical stimulation signal may or may not be paused during the second phase as desired. The non-responsive stimulation may be diurnally varied or varied on some other schedule as desired. The brain electrical activity may be detected in a variety of ways including scalp electrodes, cortical electrodes, or the electrical activity may be monitored at a depth within the brain. The responsive electrical stimulation signal may be applied to one or more electrodes placed on or about the brain. If multiple electrodes are chosen, either for measurement of the brain electrical activity or application of the responsive stimulation, the electrodes may be chosen so that they are independently selectable if so desired. The responsive stimulation (and the non-responsive stimulation) may be defined by parameters such as the electrode or electrodes selected, pulse width, inter-pulse interval (or frequency), pulse amplitude, pulse morphology (including the use of continuous waveforms such as trapezoidal, quasi-sinusoidal or sinusoidal morphologies, or pulse morphologies where each phase of the pulse is triangular, trapezoidal, a haversine, or other shape), the number of pulses in the burst (or the number of cycles, if a continuous waveform morphology is used), the number of bursts, and the intervals between bursts. Each of these parameters for either the responsive or the non-responsive stimulation may be changed or left static during a mode of the process.
The procedure may include a pause of the responsive stimulation for detection of or measurement of brain electrical activity. This may then be followed by either re-commencement of the non-responsive stimulation, or, if the desired cessation of epileptiform activity has not been achieved, by a continuation of the responsive stimulation.
The procedure may also i
Archer Stephen T.
Pless Benjamin D.
Getzow Scott M.
NeuroPace, Inc.
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