Teaching Video NeuroImages: Almost no eye movements to the left.

A 31-year-old patient had acute dizziness and lateropulsion to the right. Neuro-ophthalmologic examination revealed (1) a saccade and gaze palsy to the left (video 1, part A), (2) a “half-pathologic” head-impulse test to the right (video 1, part B), but (3) bilaterally normal adduction during convergence reaction (video 1, part C), findings typical for a left abducens nuclear palsy. It was caused by a histologically proven cavernoma in the tegmentum pontis (figure). To differentiate an abducens nuclear palsy from a combined lateral and contralateral medial rectus muscle palsy, one must test the convergence reaction, which goes via direct pathways to the oculomotor nucleus.1