Study of the excitability cycle of the blink reflex in Huntington's chorea.

The trigemino-facial reflex was studied in 7 patients affected by Huntington's chorea and in 10 patients affected by Parkinson's disease. The results show a different behavior of the habituation phenomenon in the two groups of patients: it is enhanced in the choreic and abolished in the parkinsonian patients. The main changes concern the time course of the second phase (the first inhibitory phase) of the reflex excitability cycle, in fact, the inhibitory phase appears very pronounced and prolonged in huntingtonian patients and reduced or abolished in parkinsonian patients. Some pathophysiological mechanisms involved in the control of the trigeminofacial reflex excitability are discussed with particular regard to the role of the hemispheric structures.