Supranuclear gaze palsy and eyelid apraxia in postencephalitic parkinsonism.

We describe six patients with clinicopathologically confirmed post-encephalitic parkinsonism (PEP) in whom oculomotor abnormalities developed several years after suffering the initial episode of encephalitis lethargica. Four of the cases had vertical supranuclear gaze palsy and two eyelid apraxia, features typically associated with progressive supranuclear palsy (PSP). Our findings indicate that the presence of gaze palsy alone may not be a reliable clinical discriminator between PEP and PSP. Involvement of the dorsal central gray nucleus, nucleus centralis pontis oralis, nucleus dorsal raphe interpositus, rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), nucleus interstitialis of Cajal, nucleus of the posterior commissure, pedunculopontine nuclei and frontal cortex was observed in several of our PEP cases and may contribute to the oculomotor abnormalities in this disorder. Whether the dorsal tegmental nucleus, caudal to the supratrochlear nucleus, severely affected in all our PEP cases, has a role in vertical gaze needs to be further studied.