riMLF Syndrome from Artery of Percheron Stroke

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: 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. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This is a 65 year-old-man who suffered the abrupt onset of loss of consciousness followed by difficulty looking down. MRI demonstrated 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, injury to the riMLFs was felt to be incomplete given fair upward saccades. https://collections. lib.utah.edu/ark:/87278/s6qg2g63