[Right-left dissociation of voluntary eyelid closure following right middle cerebral artery infarction]

We encountered two patients with right middle cerebral artery infarction who showed a unique eye sign not described so far. Both had suddenly developed central facial weakness, hemiplegia and hemisensory deficit in the left side. Anosognosia for the left hemiplegia, motor impersistence and left unilateral spatial neglect were also present. Initially they showed difficulty in keeping their eyes closed to the same degree on both eyes. However, this symmetrical motor impersistence of eye closing developed into a differential pattern over the days. Thus, on verbal command to close the eyes, the right eye in the non-paretic side would be closed continuously and excessively and in the left eye in the paretic side would be closed slightly and impresistently. This dissociation of eye closure was not observed in spontaneous eye closure. This symptom is close to the contralateral motor impersistence of eye closure which has been attributed to the right hemispheric lesion. But the concurrence of the ipsilateral overcontraction of the orbicularis oculi has not been described to the authors' knowledge. We proposed a hypothesis on this unique right-left dissociation of eye closing behavior.