X-linked recessive aqueductal stenosis without macrocephaly.

A normocephalic, severely retarded boy with a family history suggesting aqueductal stenosis was found by computerized tomography to have aqueductal stenosis. His parents' concurrent pregnancy was monitored by ultrasonography and amniocentesis; these disclosed a male fetus which developed marked hydrocephalus after the 20th week. The pregnancy was terminated and an autopsy of the fetus demonstrated several major CNS malformations in addition to a very narrowed aqueduct. This case illustrates the diffuse CNS disease present in at least some cases of X-linked aqueductal stenosis (XLAS) and the importance of considering this variable syndrome in normocephalic, non-dysmorphic mentally retarded males. Important aspects of the prenatal diagnosis of XLAS are also illustrated.