Spontaneous and reflex activity of facial muscles in dystonia, Parkinson's disease, and in normal subjects.

Objective: The blink rate is an index which can be easily obtained during the clinical examination, but it has not yet been properly standardised. The present study was undertaken to collect data on the age dependent development of this index and on possible abnormalities in Parkinson's disease and dystonia.
Methods: The blink rate and the rate of perioral movements were measured in 156 normal controls, 51 patients with Parkinson's disease, 48 patients with spasmodic torticollis, 14 patients with generalised dystonia, and 12 patients with focal hand or leg dystonias and have been correlated with the results of testing the orbicularis oculi reflex, the palmomental reflex, and the perioral reflex.
Results: No age related effects were found for the blink rate and perioral movements but all the reflexes showed age dependent variations. It is sufficient to measure the blink rate for one minute, provided standardised conditions are applied. Blink rate and perioral movement rate were positively correlated in patients and controls. The blink rate was significantly increased in spasmodic torticollis and decreased in Parkinson's disease. In generalised dystonia the blink rate was increased but in hand and leg dystonia the blink rate was normal. The reflex tests did not significantly differ between the subject groups except for the orbicularis oculi reflex, which was hyperexcitable in Parkinson's disease.
Conclusion: Measuring the blink rate can assist the diagnosis of extrapyramidal disorders as a soft sign, but is not very sensitive. The group differences found indicate a decrease of the blink rate and perioral movements in hypokinetic and an increase in hyperkinetic extrapyramidal disorders such as spasmodic torticollis and generalised dystonias. This may be of interest for future pathophysiological studies.