Periodic alternating ping-pong gaze.

A patient had periodic alternating Ping-Pong gaze and massive bilateral ischemic cerebral infarction proved at autopsy. In previous cases, bilateral hemisphere involvement appears to have been common in most cases. Eye movements in Ping-Pong gaze are similar to the slow-eye movements seen in sleep, anesthesia, and other obtunded states, a result of disinhibition of inherent rhythms in the oculovestibular system. They are like release phenomena and appear whenever fixational ability is lost or suspended, and during full consciousness they are inhibited by supranuclear cortical mechanisms. Ping-Pong gaze represents a distinct third variety of periodic alternating gaze disturbance, and the differential diagnostic features between it and periodic alternating gaze deviation and periodic alternating nystagmus are discussed.