Saccades abnormal; Vestibulo-ocular reflex and head impulse testing normal; Pursuit normal; Vertical gaze palsy; Downgaze palsy; Mesencephalon
Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, The Johns Hopkins School of Medicine
This is a 65-yo-man who suffered the abrupt onset of loss of consciousness followed by difficulty looking down. MRI showed bilateral rostral midbrain strokes in the distribution of the artery of Percheron. He could not initiate downward saccades and had fair upward saccades. However, downward vestibulo-ocular reflex and smooth pursuit was preserved, thus supporting the supranuclear origin of his downward motility issues. Although the riMLF is responsible for initiation of vertical saccades, projections to the depressor muscles are ipsilateral whereas projections to the elevator muscles are bilateral - therefore, unilateral riMLF damage will cause difficulty with initiation of downward>>upward saccades, while bilateral damage generally abolishes all vertical and torsional saccadic movements. In his case, bilateral riMLF function was not completely abolished given fair upward saccades.
Spencer S. Eccles Health Sciences Library, University of Utah