Periodic alternating esotropia

Periodic alternating esotropia (PAE) is a rare ocular motility disturbance observed in association with periodic alternating gaze deviation (PAG) or periodic alternating nystagmus. We examined a 9-month-old developmental^ delayed girl who showed PAE occurring synchronously with PAG. The ocular motility disorder consisted of rhythmic alternating fixation with the right eye in abduction, a left face turn and esotropia of the left eye (90 seconds), a changeover phase (10 to 15 seconds) during which the eyes are straight and the head is upright, then fixation with the left eye in abduction, a right face turn, and esotropia of the left eye (90 seconds). There was no spontaneous jerk nystagmus present. These findings continued incessantly during a follow-up period of 18 months. Magnetic resonance imaging revealed pronounced cerebellar vermis hypoplasia. Only three clinically similar cases have been previously reported, but none had been studied with modern neuroimaging techniques.