Blink reflex in dyskinetic and nondyskinetic patients with Parkinson's disease.

An electrophysiological study of the blink Reflex was undertaken in 40 dyskinetic and 20 nondyskinetic patients with Parkinson's disease, who were matched for age, stage of disease, duration of illness and amount and nature of antiparkinsonian medication. We found that latencies of R2 responses (both ipsilateral and contralateral) were prolonged in the dyskinetic group compared to the nondyskinetic group. Moreover, the late response was more easily inhibited by conditioning stimulation in dyskinetic patients. This behavior of late response in dyskinetic parkinsonians may be attributed to the reinstatement of dopaminergic suppressive control over the segmental multisynaptic systems belonging to the reflex.