Involuntary closure of eyelids in parkinsonism. Electrophysiological evidence for prolonged inhibition of the levator palpebrae muscles.

Involuntary closure of eyelids (ICE), a phenomenon variously interpreted as blepharospasm and apraxia of lid opening, is occasionally observed in parkinsonism. Nine patients (4 with Parkinson's disease, 2 with post-encephalitic parkinsonism, and 3 with supranuclear palsy) with prominent ICE, were studied by electromyographic recording of the eye muscles. ICE episodes were shown to be dependent upon prolonged, irregular inhibition of the normal tonic activity of the levator palpebrae superioris (LPS) muscle causing drooping of the upper eyelid without any corresponding activation of the orbicularis oculi (OO) muscle. Nevertheless, some degree of excessive, widely fluctuating OO activity was present in seven of the patients. Blepharocolysis (from Gr. blepharon, eyelid, and kolysis inhibition) is put forward as the term to designate ICE episodes resulting from abnormally long inhibition of the LPS muscles and should be differentiated electrophysiologically from blepharospasm, excessive OO muscles activity. Abnormal influences from basal ganglia acting on brainstem structures that regulate blinking may falicitate either of the two components of normal blinking resulting in ICE due to the predominance of LPS inhibition (blepharocolysis), the predominance of OO activation (blepharospasm) or a combination of the two.