Extradural leads, neurostimulator assemblies, and processes...

Details Extradural leads, neurostimulator assemblies, and processes... Extradural leads, neurostimulator assemblies, and processes...

2000-11-09

2003-03-04

Rivell, John (Department: 3753)

Surgery

Diagnostic testing

Detecting brain electric signal

C600S378000, C607S045000, C607S116000

Reexamination Certificate

active

06529774

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to a neurostimulator that is preferably implantable and is suitable for treating epilepsy and other neurological disorders. The invention includes inventive leads that are suitable both for providing electrical somatosensory stimulation, extradurally applied, as well as electrical stimulation that is applied to the central nervous system. The leads are preferably also suitable for sensing electrical signals in the brain. The invention includes processes of using the neurostimulator and its leads.
The neurostimulator may independently provide a variety of different electrical stimulation, e.g., non-responsive electrical stimulation signals applied to the central nervous system to reduce the likelihood of a seizure or other undesirable neurological even from occurring, electrical stimulation signals applied to the central nervous system when the neurostimulator determines that epileptiform waveforms are impending or extant, and extradural electrical somatosensory stimulation signals.
The responsive electrical stimulation signal or signals are intended to terminate epileptiform activity, e.g., to desynchronize abnormally synchronous brain electrical activity.
BACKGROUND OF THE INVENTION
Epileptic seizures are characterized by hypersynchronous 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 seizures 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 either 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 promising method of treating patients having epileptic seizures is electrical stimulation of the brain.
Since the early 1970's, electrical brain stimulators have been used which 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 Edition, Pleman Press, N.Y. 1974. Others have utilized devices which stimulated the centro median nucleus of the thalamus. See, “Electrical Stimulation of the Centro Median Thalamic Nucleus in Control of Seizures: Long Term Studies.” F. Valasco 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
, Volume 370, 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 17 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.
Responsive brain 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
, Vol. 35, supplement 4, 1995.
Finally, in conjunction with direct brain tissue stimulation, electrical signals that are applied to regions of the body which are not neurological tissue, e.g., applied extradurally to the skin and particularly to the scalp, have been shown to be useful in delaying or preventing the onset of a seizure.
In applying the various electrical stimuli to the brain, a number of different electrode configurations are known.
U.S. Pat. Nos. 4,702,254, 4,867,164, and 5,025,807, each to Zabara, show a device for controlling or preventing involuntary movements such as caused by epileptic seizures. The device is made up of an electrical pulse generator, a positive electrode to be applied to a person's body, and a negative electrode to be placed adjacent the vagus nerve in that body.
U.S. Pat. No. 4,735,208, to Wyler et al., shows a subdural strip electrode for determining epileptogenic foci. The strip has a long, tapered proximal end portion terminating in a narrow tip from which a number of wires extend. This is said to allow withdrawal of the strip electrode without a substantial incision. Strip width and thickness are said to be such that the strip may be withdrawn after extended implantation without the need for surgery. In one variation, the central region of the strip is significantly reinforced.
U.S. Pat. No. 4,903,702, to Putz, shows an electrical brain-electrode device for increased accuracy in determining epileptogenic foci. This device has a dielectric base member and an array of electrodes mounted on that base member. Each of the electrodes has a separate wire for connection to a measurement device. The device preferably has radio-opaque regions adjacent to at least one of the electrodes such that the position of the electrodes with respect to the brain may be more readily determined by x-ray.
U.S. Pat. No. 5,097,835, also to Putz, shows a subdural electrode for determining epileptogenic foci. The device is said to have dielectric layers and at least one electrode disc placed between the layers. The disc includes a tab. The accompanying lead wire is folded over the outer segment of the tab so that the tab crimps the wire. The electrical and mechanical integrity of the connection is improved by wrapping the wire about the tab several times before crimping.
U.S. Pat. Nos. 5,702,429, 5,814,092, and 5,913,882, each to King, show a neural stimulation technique with feedback and further shows a variety of stimulating and recording leads (e.g., #
10
in
FIG. 1
discussed at column
2
beginning at line
21
) and other embodiments shown in
FIGS. 2-5
. King shows (beginning at column
3
, line
60
) the manner of using the stimulating electrodes (
18
-
21
) and the recording electrodes (
25
-
26
). Generally, the placement of the electrodes is said to be “at sites adjacent electrically excitable tissue for control of conscious paresthesia into the painful area of a patient.” The patent goes on to explain that: “electrically excitable tissue includes neural tissue intrinsic to the heart and other organs, a peripheral nerve, the spinal cord surface, the interior of the spinal cord, deep brain tissue,

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