Parinaud's Syndrome with downgaze palsy.

The Sylvian aqueduct syndrome was first clearly delineated by Kestenbaum in 1946.

The clinical features of this syndrome were reviewed by Smith et al.; they consist of pupillary anomalies for example, anisocoria and absence of the light reaction; impairment of conjugate upward gaze; convergence nystagmus occurring as a substituted movement on attempted conjugate upward gaze; retractory nystagmus, which is usually inconstant; vertical nystagmus on gaze upward or downward, and palsies of extraocular muscles. In all previously reported cases this syndrome has been associated with fixed, structural lesions in the rostral periaqueductal region.