Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-11-28
2003-07-22
Hoang, Tu Ba (Department: 3742)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S045000, C600S544000
Reexamination Certificate
active
06597954
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to systems and methods for treating neurological disorders, and more particularly to a system and method employing an electronic device for sensing and detecting neurological dysfunction, specifically neuronal activity characteristic of epileptic seizures, in one region of a patient's brain, and applying treatment in response thereto in another region of the patient's brain.
Epilepsy, a neurological disorder characterized by the occurrence of seizures (specifically episodic impairment or loss of consciousness, abnormal motor phenomena, psychic or sensory disturbances, or the perturbation of the autonomic nervous system), is debilitating to a great number of people. It is believed that as many as two to four million Americans may suffer from various forms of epilepsy. Research has found that its prevalence may be even greater worldwide, particularly in less economically developed nations, suggesting that the worldwide figure for epilepsy sufferers may be in excess of one hundred million.
Because epilepsy is characterized by seizures, its sufferers are frequently limited in the kinds of activities they may participate in. Epilepsy can prevent people from driving, working, or otherwise participating in much of what society has to offer. Some epilepsy sufferers have serious seizures so frequently that they are effectively incapacitated.
Furthermore, epilepsy is often progressive and can be associated with degenerative disorders and conditions. Over time, epileptic seizures often become more frequent and more serious, and in particularly severe cases, are likely to lead to deterioration of other brain functions (including cognitive function) as well as physical impairments.
The current state of the art in treating neurological disorders, particularly epilepsy, typically involves drug therapy and surgery. The first approach is usually drug therapy.
A number of drugs are approved and available for treating epilepsy, such as sodium valproate, phenobarbital/primidone, ethosuximide, gabapentin, phenytoin, and carbamazepine, as well as a number of others. Unfortunately, those drugs typically have serious side effects, especially toxicity, and it is extremely important in most cases to maintain a precise therapeutic serum level to avoid breakthrough seizures (if the dosage is too low) or toxic effects (if the dosage is too high). The need for patient discipline is high, especially when a patient's drug regimen causes unpleasant side effects the patient may wish to avoid.
Moreover, while many patients respond well to drug therapy alone, a significant number (at least 20-30%) do not. For those patients, surgery is presently the best-established and most viable alternative course of treatment.
Currently practiced surgical approaches include radical surgical resection such as hemispherectomy, corticectomy, lobectomy and partial lobectomy, and less-radical lesionectomy, transection, and stereotactic ablation. Besides being less than fully successful, these surgical approaches generally have a high risk of complications, and can often result in damage to eloquent (i.e., functionally important) brain regions and the consequent long-term impairment of various cognitive and other neurological functions. Furthermore, for a variety of reasons, such surgical treatments are contraindicated in a substantial number of patients. And unfortunately, even after radical brain surgery, many epilepsy patients are still not seizure-free.
Electrical stimulation is an emerging therapy for treating epilepsy. However, currently approved and available electrical stimulation devices apply continuous electrical stimulation to neural tissue surrounding or near implanted electrodes, and do not perform any detection—they are not responsive to relevant neurological conditions.
The NeuroCybernetic Prosthesis (NCP) from Cyberonics, for example, applies continuous electrical stimulation to the patient's vagus nerve. This approach has been found to reduce seizures by about 50% in about 50% of patients. Unfortunately, a much greater reduction in the incidence of seizures is needed to provide clinical benefit. The Activa device from Medtronic is a pectorally implanted continuous deep brain stimulator intended primarily to treat Parkinson's disease. In operation, it supplies a continuous electrical pulse stream to a selected deep brain structure where an electrode has been implanted.
A typical epilepsy patient experiences episodic attacks or seizures, which are generally defined as periods of abnormal neurological activity. As is traditional in the art, such periods shall be referred to herein as “ictal” (though it should be noted that “ictal” can refer to neurological phenomena other than epileptic seizures).
Known work on detection and treatment of epilepsy via electrical stimulation has focused on a region of the brain frequently referred to as an epileptic (or epileptogenic) focus, particularly in patients suffering from partial epilepsy (the most common form of adult-onset epilepsy). In at least some partial epilepsy sufferers, it is the area where hypersynchronous activity consistently begins; it typically spreads outward, and into other regions of the brain, from there. The characteristics of an epileptic seizure onset are different from patient to patient, but are frequently consistent from seizure to seizure within a single patient. Although seizures in a partial epilepsy sufferer frequently begin in the same region of the brain, they may secondarily generalize quickly to cover a significant portion of the brain. Patients with primary generalized epilepsy may not have any specific identifiable seizure origin.
Unfortunately, continuous stimulation of deep brain structures for the treatment of epilepsy has not met with consistent success. To be effective in terminating seizures, it has traditionally been believed that epilepsy stimulation should be performed near the focus of the epileptogenic region. The focus is often in the neocortex, where continuous stimulation may cause significant neurological deficit with clinical symptoms including loss of speech, sensory disorders, or involuntary motion. Accordingly, research has been directed toward automatic responsive epilepsy treatment at or near the focus, based on a detection of imminent seizure.
Recent research, however, indicates that the concept of a single epileptic focus does not necessarily accurately reflect the origins of partial epilepsy, at least in humans. See J. Engel, Jr., Intracerebral Recordings: Organization of the Human Epileptic Region, J. Clin. Neurophysiol. 1993; 10(1): 90-98. The human brain is a complex system, and although an anomalous signal may first be detected via known methods at a particular location or region, that does not necessarily imply that area is the true epileptogenic origin of an epileptic seizure. Nor is the region where abnormal signals are first identified necessarily the location where it is most effective to treat a seizure or its precursor. In fact, it is possible to have multiple locations in a single patient's brain that all act as epileptic foci. And in generalized seizures, abnormal EEG signals can be found throughout a patient's brain practically simultaneously.
Most prior work on the detection and responsive treatment of seizures via electrical stimulation has focused on analysis of electroencephalogram (EEG) and electrocorticogram (ECoG) waveforms. In general, EEG signals represent aggregate neuronal activity potentials detectable via electrodes applied to a patient's scalp, and ECoGs use internal electrodes near the surface of the brain. ECoG signals, deep-brain counterparts to EEG signals, are also detectable via electrodes implanted under the dura mater, and usually within the patient's brain. Unless the context clearly and expressly indicates otherwise, the term “EEG” shall be used generically herein to refer to both EEG and ECoG signals.
Much of the work on detection has focused on the use of time-domain analysis of EEG s
Fischell David R.
Fischell Robert E.
Pless Benjamin D.
Hoang Tu Ba
NeuroPace, Inc.
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