[Pathology of congenital aqueductal stenosis and posthemorrhagic hydrocephalus].

The brain stem of children with congenital aqueductal stenosis or posthemorrhagic hydrocephalus were examined histologically and immunohistochemically. Congenital aqueductal stenosis occurs in various stages of CNS development, and is associated with microdysplasia and maturational abnormalities including astrogliosis, loss of neurons (tyrosine hydroxylase reactivity) and decreased myelination (myelin basic protein reactivity) in the periaqueductal gray matter. In Arnold-Chiari type II malformation there are few dysplasias, and poor development of glial and neural components in the periventricular brainstem. On the other hand, there are marked astroglial proliferation and defects of neural fibers in the periaqueductal area in children with posthemorrhagic hydrocephalus. Fibrous proliferation in aqueduct makes stenosis, and its pathogenesis seems to be caused by edema, ependymal cell desquamation, microglial proliferation and astrogliosis in parts of hemosiderin deposition. Thus, different CSF circulation disturbance and neural transmission disorder of the brainstem may develop with occurrence time, etiology or secondary complication of hydrocephalus.