Ocular tilt reaction with vertical eye movement palsy caused by localized unilateral midbrain lesion

A 60-year-old man developed diplopia and experienced difficulty moving his eyes. Vertical movement of each eye, including vestibulo-ocular reflex and smooth pursuit, was extremely limited. Horizontal eye movements were normal. His head position was tilted toward his left. There was 10 prism diopters of exotropia and 10 prism diopters of right hypertropia. Fundus photographs revealed a clockwise torsion of both eyes. These signs indicate leftward ocular tilt reaction. Magnetic resonance imaging showed a small area of an increased signal intensity localized in the midbrain dorsomedial to the red nucleus on the right side. Based on recent experimental evidence, it may be assumed that the unilateral lesion involving the right interstitial nucleus of Cajal most probably caused leftward ocular tilt reaction in our patient.