Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-07-28
2003-09-16
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06622047
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods and apparatus for treating or controlling medical, psychiatric or neurological disorders by application of modulating electrical signals to a selected nerve or nerve bundle of the patient, and more particularly to techniques for treating patients with neuropsychiatric disorders by application of such signals to the vagus nerve or other suitable cranial nerve, using an implantable neurostimulator. Specifically, the invention is directed toward treating the symptoms of neuropsychiatric disorders such as schizophrenia, depression, and borderline personality disorder, by selective modulation of vagus nerve activity.
Although schizophrenia was initially thought to have only psychological origins, more recent psychobiology and psychopharmacology findings have indicated that the illness is primarily organic in nature. Electrophysiologic studies of patients with schizophrenia have supported an organic etiology. Although not entirely consistent, electroencephalogram (EEG) studies have tended to reveal abnormalities in these patients. Also, some parallels have been found between schizophrenia and epilepsy.
Developments in psychobiology and psychopharmacology have also provided considerable evidence that major depressive disorder and bipolar depression are biological rather than psychological diseases. The conclusion that depression has a biological basis is also supported by numerous electrophysiological and endocrine studies. Deficiency of brain neurotransmitters has been associated with depression. In particular, abnormally low concentrations of the neurotransmitter serotonin and its metabolites and norepinephrine have been found in depressed patients. Several serotonin uptake inhibitors, which increase the amount of serotonin at the synapse have been shown to be effective antidepressants. Iincreased activity of the vagus nerve has been postulated to be associated with release of increased amounts of serotonin and norepinephrine in the brain.
Borderline personality disorder is a poorly understood, but recognized psychiatric disorder which seems to have some overlap of schizophrenia and depression. Patients tend to be poorly functional without florid psychosis or overt depression. Lahmeyer et al. reported, in
J. Clin. Psych
. (1989) 50(6):217-225, that sleep architecture in patients with borderline personality disorder is disturbed in that REM latency is decreased and REM density is increased. This was found to be particularly true if patients suffered coexisting depression, a history of affective illness or a family history of psychopathology. Sleep abnormalities were reported to appear similar to those seen in affective disorders.
It is an object of the present invention to apply the techniques of selective modulation of vagus nerve electrical activity, using a neurostimulator device which may be implantable, or used external to the body with only a small portion of the circuitry implanted or with only the nerve electrode(s) and associated lead(s) implanted percutaneously in the body, to the treatment of neuropsychiatric disorders including schizophrenia, depression, and borderline personality disorder, as well as other neuropsychiatric disorders as defined in the Diagnostic and Statistical Manual of Mental Disorders.
In U.S. Pat. No. 5,299,569 (sometimes referred to herein as “the '569 patent”), assigned to the same assignee as the present application, Wernicke et al disclosed methods and devices for treating and controlling certain neuropsychiatric disorders by selective stimulation of the vagus nerve. A neurostimulator which is preferably but not necessarily implantable selectively applies the therapy to treat the specific neuropsychiatric disorder such as schizophrenia, depression, borderline personality disorder, or other related disorder. The therapy is delivered in a manner to stimulate or modulate the vagal activity of the patient in a predetermined manner to treat and relieve the symptoms of the disorder, although it may not be effective in alleviating the underlying root cause of the disorder. The neurostimulator is programmed by the attending physician to generate a pulsed electrical signal that provides the desired therapeutic modality for treatment.
In the '569 patent, the applicants reported their conclusion that vagal stimulation can be effective for treating schizophrenia, for example. One observation toward that conclusion is that fast desynchronous (beta) activity and paroxysmal (synchronous) activity of the EEG have both been reported in studies of this disorder. At some stimulation parameters, vagal stimulation will synchronize the EEG, with a resultant beneficial effect on treatment of the disorder where increased beta wave activity is present. A second observation is the apparent relationship between schizophrenia and temporal lobe epilepsy. The temporal lobes are part of the limbic system, which they postulated is malfunctioning in patients with schizophrenia. Vagal stimulation can suppress temporal (complex partial) seizures, which are generated in the limbic system. The structures of this system are interconnected, and the beneficial effect of vagal stimulation seen in the temporal lobes may be transmitted to other brain structures, leading to a similar effect on schizophrenia. In this case, the abnormality being treated is a synchronous paroxysmal (epileptiform) discharge, and the therapy is designed to desynchronize the EEG.
In the treatment, different signal parameters and threshold curves are used to activate the various fibers of the patient's vagus nerve for selective modulation thereof by appropriately setting pulse width and amplitude of the electrical signal to be delivered by the neurostimulator to the patient's vagus nerve. It was recommended that to increase desynchronous activity of the EEG for treatment of a neuropsychiatric disorder, it would be prudent to use a short pulse train for the stimulus because the fibers could become refractory to the stimulation within a relatively short time interval. Then, after a suitable recovery period, another short pulse train may be applied to achieve further treatment. The precise pattern to be used, including the length of the time intervals on and off, depends upon and is adjusted to the individual patient and the particular disorder being treated.
The basic stimulation strategy called for modulating the activity of a number of brain structures, including the limbic system, the reticular formation, and the hippocampus through selective stimulation of the vagus nerve, which projects directly or indirectly to these brain structures. The strategy may be implemented by circadian programming to automatically activate the stimulus generator to continuously, periodically or intermittently generate an electrical signal appropriate for application to the patient's vagus nerve to modulate its activity and that of these brain structures. In another aspect, the treatment is carried out by applying the selectively modulating electrical signals to the patient's vagus nerve in response to the occurrence of one or more predetermined detectable events.
In the case of depression, vagal stimulation may be used to alter sleep state architecture as a modality that may produce a beneficial antidepressant effect. Certain stimulation parameters for the vagus nerve may produce synchronization of brain activity which leads to the biochemical changes required to relieve depression, without causing seizures. It is also noted in the '569 patent that vagal stimulation may be effective in the treatment of borderline personality disorder, at least because of the abnormalities in sleep architecture attendant with such disorders and the capability of vagal stimulation to alter sleep states. Recently, left cervical vagus nerve stimulation has been shown to have antidepressant effects in the treatment of patients with major depression and bipolar disorder (Rush et al,
Biological Psychiatry
, February, 2000).
Methods and appar
Barrett Burke T.
Terry, Jr. Reese S.
Blank Rome LLP
Cyberonics, Inc.
Getzow Scott M.
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