Chronic cerebellar stimulation (CCS) and deep brain stimulation (DBS) in involuntary movement disorders.

Motor disorders of disinhibition may be modified by prosthetic mobilization of CNS inhibitory mechanisms by chronic electrical stimulation of the cerebellar cortex (CCS) and by deep brain stimulation of the thalamus and internal capsule (DBS). Reduction in spasticity, abnormal movements, intractable epilepsy and aggressive behavior has been reported after CCS, although negative results in human and animal studies have been published. No adverse neurologic, psychologic or intellectual effects of stimulation have occurred after 7 years of CCS, although subclinical histological changes may occur in the cerebellar cortex under the electrodes. CCS has been shown to produce physiological changes in evoked potentials, motoneurone excitability, epileptic discharges in the EEG and quantitative changes in movement. Surface and deep thalamic recordings have shown reduced amplitudes of somatosensory responses after CCS. Over the last 2 years we have employed chronic deep brain stimulation (DBS) in 49 patients with clinically useful results in half the patients. The technique allows reversible modification of movement disorders, and the technique can be used on the second side after a previous thalamectomy. Physiological testing, direct thalamic recordings and quantitative analysis of movement have allowed assessment of optimal rate and voltage of stimulation. For some intractable movement disorders DBS has effected significant therapeutic results when all other therapeutic techniques have failed.