Arnold-Chiari malformation. Report of four cases with contamination of the central nervous system by amniotic contents.

Four patients with the Arnold-Chiari malformation had massive prenatal contamination of the spinal cord and brainstem (and also of the cerebral ventricles in one case) by amniotic squamous cells and lanugo hair, which had entered through open meningomyeloceles. Amniotic contents were present in the subarachnoid space, central canal, fourth ventricle, and aqueduct and were also embedded in neural tissue, causing severe gliosis, fibrosis, and blockage. The mechanism of the complication and its implications in the prognosis of patients with the Arnold-Chiari malformation are discussed.