Periaqueductal microdysplasia in children with congenital aqueductal stenosis.

The brainstems of children with aqueductal stenosis (AS) and controls were examined histologically and immunohistochemically. In the periaqueductal area of children with AS, there was astrogliosis, loss of neurons (tyrosine-hydroxylase (TH) reactivity) and decreased myelination (myelin basic protein reactivity). In locus coeruleus, there was a decreased neuronal cell density (TH-positive neurons) in those with AS. In other areas of the brainstem (medial reticular formation), there appeared to be more TH and substance P reactive neurons. These alterations (dysplasia of slight degree) in neurons were more remarkable in children with AS with other identified brain anomalies than in those with only AS, judged by specific immunocytochemical identification of neurons. The periaqueductal astrogliosis and delayed/insufficient myelination suggest secondary damage to this region.