Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-08-31
2003-07-08
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S076000
Reexamination Certificate
active
06591138
ABSTRACT:
FIELD OF THE INVENTION
This invention is in the field of devices for the treatment of neurological disorders in human subjects, particularly those disorders that originate in the brain.
BACKGROUND OF THE INVENTION
The current state of the art in treating neurological disorders such as epilepsy or Parkinson's disease involves either drugs, destructive nigral lesions or the open-loop electrical stimulation of neurological tissue. Drug therapy has been shown to have significant short and long-term side effects and is often ineffective. In U.S. Pat. No. 3,850,161, Liss describes a continuous closed-loop feedback system which will always feedback part of the brain EEG signal to separate electrodes so that if a large EEG signal occurs it will be fed back in an attempt to cancel out the original signal. This system does not take advantage of recently developed digital signal processing and microcomputer technology by which feedback signals can be activated only when a neurological event occurs, nor does it provide a practical way to recognize and intervene during early stages in the evolution of a neurological event. In addition, the Liss device is not programmable and it does not provide any capability to record EEG signals. Examples of a “neurological event” are the occurrence of an epileptic seizure, a tremor or the occurrence of a migraine aura or migraine headache. A “neurological event” is defined herein as either the precursor of an event such as an epileptic seizure, or the event itself. This concept of detecting an electrical precursor that is a first type of neurological event that occurs some time before the “real” event (i.e. anomalous brain electrical activity or a particular pattern of neural activity associated with clinical symptoms) is an important aspect of the present invention. It has been shown that both epileptic seizures and Parkinson's tremors have precursors that occur before and can be used to predict the onset of the clinical symptom. It is also very likely that other neurological events such as migraine headaches and depression would have anomalous electrical activity predictive of the onset of clinical symptoms. Methods for prediction of epileptic seizures have been published by Elger and Lehnertz (in Elger, C. E., and Lehnertz, K., “Seizure prediction by non-linear time series analysis of brain electrical activity,” Eur. J. Neurosci. 1998 Febuary; 10(2): 786-9, and Osorio, Frei and Wilkinson (in Osorio, I., et al., “Real-time automated detection and quantitative analysis of seizures and short-term prediction of clinical onset,” Epilepsia 1998 June; 39(6): 615-27).
Maurer and Sorenson in U.S. Pat. No. 4,019,518 describe a combined internal/external system for electrical stimulation of the body with biphasic pulses but do not describe any means of detecting neurological events. Fischell in U.S. Pat. No. 4,373,527 describes a programmable medication infusion system but does not anticipate its use in response to a detected neurological event.
More recently, a device has been approved for human use to stimulate the vagus nerve in a continuous fashion with the objective of decreasing the rate of epileptic seizures. Clinical reports on such devices indicate only a modest degree of success in that only 50% of the patients experience a greater than 20% reduction in the rate of epileptic seizures. Another device that has been recently introduced into clinical practice utilizes intermittent or continuous stimulation of the thalamus for the treatment of involuntary motion disorders such as Parkinson's syndrome. Neither of these two open-loop devices described above is highly effective for the treatment of a neurological disorder such as epilepsy, and neither anticipates the use of decision making in order to optimize a response to terminate the precursor of a neurological event or the neurological event itself; nor does either device allow for the recording of EEG signals. In addition, both known devices use stimulation frequencies above 10 Hz, which for the reasons set a forth in detail below, are not optimal.
Fischell et al in U.S. Pat. No. 6,016,449, which is incorporated herein by reference, teaches a fully implantable neurostimulator capable of responsive treatment of neurological disorders. However, Fischell does not discuss in detail the advantageous use of low frequency stimulation as a means of inhibiting epileptiform activity.
It is well known that slow wave potentials in the brain are often inhibitory in nature yet all known stimulation attempts to treat epilepsy in humans have used relatively high frequency stimulation, in most cases greater than 20 Hz. These higher frequencies, while effective for a brain mapping type procedure, have significant potential to induce epileptogenic activity. In fact, Hallett in “Transcranial magnetic stimulation and the human brain,” Nature, Vol. 406, Jul. 13, 2000, states that while “rapid repetitive transcranial magnetic stimulation (rTMS), at frequencies of 5 Hz and higher, will transiently enhance motor excitability . . . slow rTMS, at 1 Hz will transiently depress excitability.”
SUMMARY OF THE INVENTION
There is good evidence that slow wave activity is inhibitory in the central nervous system of man (Staton, R. D. et al., “The electroencephalographic pattern during electroconvulsive therapy: V. Observations on the origins of phase III delta energy and the mechanism of action of ECT,” Clin. Electroencephalogr. 1988 October; 19(4): 176-198 and animals (Buzsaki, G. et al., “Depth profiles of hippocampal rhythmic slow activity (‘theta rhythm’) depend on behaviour,” Electroencephalogr. Clin. Neurophysiol. 1985 July; 61(1): 77-88) including such stimulation applied to the hippocampus (Leung, L. S. et al., “Theta-frequency resonance in hippocampal CA1 neurons in vitro demonstrated by sinusoidal current injection,” J. Neurophysiol. 1998 March; 79(3): 1592-6). These slow waves may be at theta frequencies (4 to 7 Hz—Buzsaki et al. 1985), delta frequencies (1 to 3 Hz—Staton et al. 1988), or even at less then 1 Hz (Contreras, D. et al., “Cellular basis of EEG slow rhythms: a study of dynamic corticothalamic relationships,” J. Neurosci. 1995 January; 15(1 Pt 2): 604-22). Psatta et al. (in “Control of chronic experimental focal epilepsy by feedback caudatum stimulation,” Epilepsia 1983 August.; 24(4): 444-54) describe successful ictal spike depression by 5 Hz stimulation of the caudate nucleus (CN) in cat brains. The article also states that stimulation of the thalamus, mesencephalic reticular formation or hypothalamus was not effective. Finally, Hallett (in “Transcranial magnetic stimulation and the human brain” Nature 2000; 406 (July 13): 147-150) discusses the inhibitory effects of low frequency pulsing from a transcranial magnetic stimulator.
The present invention includes transcranial stimulation, or direct brain stimulation from multiple electrodes, in either an open or closed-loop system for the treatment of certain neurological disorders such as epilepsy, migraine headaches and Parkinson's disease. A purpose of the present invention is to overcome the shortcomings of all known devices for the treatment of such disorders. Specifically, the present invention utilizes slow wave potentials (low frequency stimulation in a range of approximately 1 to 10 Hz) to prevent or abort a neurological event.
One embodiment of the present invention envisions a multiplicity of brain electrodes placed either within the brain, on the surface of the brain itself, or on the dura mater that surrounds the brain. Some or all of these brain electrodes may be used to directly detect an abnormal neurological event such as an epileptic seizure, or they may be used to detect a pattern of electrical activity that precedes or accompanies an abnormal neurological event. A stimulation signal can also be applied to any one, several, or all elements of such an electrode array. The is stimulation signals sent to each electrode may be identical or they may be programmed to differ in amplitude, frequency, waveform, phase and time duration. I
Fischell David R.
Upton Adrian R. M.
NeuroPace, Inc.
Schaetzle Kennedy
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