- A review of the clinical results from 200 patients and the neurophysiological results from 42 patients suggests that chronic cerebellar stimulation (c.c.s.) can improve cerebral palsy and reduce intractable seizures. The therapeutic effects of stimulation of the cerebellar surface may not be due to activation of Purkinje cells. There is evidence that stimulation of brainstem structures, particularly the reticular formation, may be associated with thalamic inhibition; such effects would explain the clinical results of c.c.s. as well as the reduction in amplitude of reflexes, evoked potentials, and paroxysmal discharges in the electroencephalogram. This hypothesis would explain the prolonged, rebound, paradoxical, and cumulative effects of c.c.s. No clinical disturbance or significant tissue damage has resulted from c.c.s. over 5 years. The technique is an example of the therapeutic manipulation of inhibitory and disinhibitory mechanisms in the central nervous system.