[Dissociation of voluntary eye closure--to keep the eyes closed and to blink--following right hemisphere stroke].

We report a case of a unique eye sign following right hemispheric infarction. This patient was a 78 year old right-handed woman. There was a history of a left hemispheric stroke 1 year previously. On admission, she showed left hemianopia, dysarthria, mild left central facial paresis, bilateral sensory deficit and quadriparesis which were marked on the left side. Babinski sign was elicited on the left. She did not have anosognosia or visual neglect. She had mild orofacial apraxia, but ideomotor and ideational apraxia was absent. There was no motor impersistence. Magnetic resonance imaging of the brain revealed a recent infarction in the territory of the right middle cerebral artery and an old infarction in the left tempro-parietal lobe. The patient could not open her eyelids to verbal command or voluntarily until about two weeks later, when she became able to open her eyes but showed difficulty keeping her left eye closed. She was aware of this problem and could repeat the command and comprehend what was requested to her. On verbal command to close the eyes, her right eye would be closed continuously and excessively and the left eye would only blink. When requested to blink, however, she could blink correctly without excessive eye closure. Spontaneous, reflex and voluntary blinking were normal. Her eyes were closed normally during sleep. Blepharospasm was not seen. The patient showed a striking dissociation between a failure to close her eyes continuously and a preserved ability to blink voluntarily. We suggest that her ability to contract palpebral portion of her left orbicularis oculi muscle is preserved. Regarding the mechanism of the voluntary eye closure system, separate control mechanisms should exist on closing eyes continuously and blinking.