Ocular movements in essential blepharospasm.

In essential blepharospasm histopathologic and electrophysiologic evidence supports the existence of lesions in proximity to brainstem nuclei controlling ocular movements. We studied horizontal ocular movements in eight patients who had been treated previously with surgery or botulinum toxin injection to control essential blepharospasm (mean age, 58 years) and compared these with seven control subjects who did not have blepharospasm (mean age, 68 years). We examined fixation stability, saccades, the vestibulo-ocular reflex, visual enhancement and suppression of the vestibulo-ocular reflex, optokinetic nystagmus, and pursuit by using digitally sampled, direct current electro-oculography. Patients with blepharospasm exhibited no ocular movement abnormalities. Since quantitative aspects of ocular movements are sensitive to nonspecific brainstem lesions, the absence of abnormal ocular movements suggests that the lesion in blepharospasm is specifically limited to neurons regulating the facial muscles.