Excitability recovery curves of blink reflexes in patients with athetotic cerebral palsy.

We evaluated the brainstem function or its excitability by the blink reflex evoked with the electrical stimulation to the supraorbital nerve in 10 patients with athetotic cerebral palsy compared with 10 normal subjects and 7 spastic type patients. There were no differences in stimulus intensity, latency of R1 and R2 components, and duration and area of EMG activity of the R2 component of the blink reflex elicited by single stimulation among the two patients' groups and normal subjects. R1 recovery cycle to paired stimuli in the athetotic group showed a facilitation of the test responses by the conditioning stimuli at 100 and 200 ms intervals, but were not significantly different from those in the normals. On the other hand, the R2 recovery curve in the athetotic group showed a significant hyperexcitability at all intervals from 100 to 600 ms compared to the normals. Our results from the R2 hyperexcitable recovery to paired stimuli are indicative of increased brainstem interneuronal excitability in athetotic patients and similar to the results reported in the disorders of the basal ganglia, i.e. Parkinson's disease, dystonia and blepharospasm. We suggest that this hyperexcitability might be caused by abnormal input possibly from the basal ganglia upon these brainstem interneurons.