Walsh & Hoyt: Hydrocephalus

Hydrocephalus, ventricular enlargement from obstructed flow of CSF, can produce a number of neuro-ophthalmic and neurologic signs and symptoms, many of which could be considered falsely localizing. Corbett beautifully reviewed the afferent and efferent abnormalities seen in patients with hydrocephalus. Disturbances in ocular motility include unilateral or bilateral abducens nerve palsies most frequently, but also divergence paralysis, trochlear nerve palsies, and rarely partial or complete oculomotor nerve palsies. The dorsal midbrain syndrome is regularly associated with hydrocephalus of any cause and may appear as a false localizing sign if the tumor causing the hydrocephalus is not located in the upper brain stem. Corbett noted that the earliest signs of the dorsal midbrain syndrome may be light-near dissociation of the pupils, followed by gaze paretic, upbeat nystagmus occurring only in upgaze. Later, upgaze paralysis supervenes, although vertical vestibuloocular reflexes are usually preserved.