A 51-year-old woman with a history of a heart murmur and a small stroke several years earlier suddenly began walking unsteadily and noticed vertical double vision. Examination findings revealed limitation of the right eye on looking down and in (Figure 1) and mild ataxia of gait and of each arm. She had a slight spontaneous left head tilt, and additional left tilt decreased, whereas right head tilt maximized image separation, supporting the diagnosis of a right trochlear nerve palsy. Magnetic resonance image findings showed bilateral cerebellar and left pontomesencephalic tectal infarctions in the territory of the superior cerebellar arteries (SCAs) (Figure 1). Echocardiography revealed a large atrial septal defect as the avenue of a probable paradoxical embolus. During the next 2 weeks, diplopia disappeared and ataxia improved.
James R. Keane. Tectal Fourth Nerve Palsy Due to Infarction. Arch Neurol. 2004;61(2):280. doi:10.1001/archneur.61.2.280