Periaqueductal dysfunction (the Sylvian aqueduct syndrome): a sign of hydrocephalus?

A patient with hydrocephalus due to aqueductal occlusion is described in whom the Sylvian aqueduct syndrome appeared during a sudden increase in intracranial pressure. The ocular signs resolved completely when the hydrocephalus was relieved. Marked dilatation of the posterior part of the third ventricle and of the rostral aqueduct with axial displacement of these structures was demonstrated radiologically. It is suggested that the ocular signs in this case were the result of periaqueductal dysfunction due to assimilation and dilatation of the aqueduct, with secondary tentorial block. This abnormality may be the cause of the similar abnormalities commonly found in noncommunicating hydrocephalus in both infants and adults.