Eye movements in REM sleep could be controlled by the same conjugate system while awake

We describe the impairment of eye movements during REM sleep in a patient with internuclear ophthalmoplegia. A 75-year-old woman, complaining of acute unsteady gait and diplopia, was diagnosed to have right medial longitudinal fasciculus (MLF) syndrome with limited adduction of the right eye. Overnight polysomnography revealed the same impairment of right adductive ocular movement during REM sleep. Our findings suggest that the MLF mediates lateral conjugation of eye movements during REM sleep as well as voluntary lateral conjugate eye movements during wakefulness.