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The eyelid reflex in hemifacial spasms. Study in 57 patients

Abstract:

FUNDAMENTS: The blink reflex is the neurophysiologicaI method for the study of hemifacial spasm. It is a polysynaptic reflex with a primary component or R1, which is of pontine origin, and a secondary component or R2 probably originating on the pons and lateral bulb. OBJECTIVE: To study hemifacial spasm, its clinical, and demographic characteristics and the possible neurophysiological (blink reflex) differences between symptomatic and idiopathic cases. METHODS: The study population included 57 patients (35 women and 22 men) with no axonal damage on the seventh cranial nerve; the control group included 57 healthy people paired up according to age and sex. Patients underwent a CT scan or MRI. Blink reflex was studied on the healthy and damaged sides of the patient group and left side was studied in the control group. After hyperventilation the study was repeated on the affected patient group only. RESULTS: The patients' average age was 53.4 years and the average duration of the disease was 3.7 years. Thirty-four patients had proven structural anomalies and the left side was affected in the same number. When comparing the results between the damaged side, the normal one and the control side it was only significant for the R1 component (p < 0.00000). No differences were found between the symptomatic and the idiopathic cases before or after hyperventilation, that lengthened R1, R2 and R2c latency periods (p < 0.00000; 0.0007 and 0.00000, respectively). CONCLUSIONS: Blink reflex does not enable the establishment of differences between the idiopathic and the symptomatic cases. The rise of the latency periods after hyperventilation signals the beginning of hyperexcitability of the secondary facial motor nucleus due to a peripheral lesion, to loss of supranuclear inhibitory control or both.