Arnold-Chiari malformation: report of a case with contamination of ventricular and subarachnoid spaces by amniotic sac contents.

An infant with the Arnold-Chiari malformation had a lumbosacral amniotic-central nervous system fistula that allowed massive amounts of squamous cells and lanugo hair to enter the ventricular and subarachnoid spaces causing blockage, gliosis, and fibrosis. This rare complication can be diagnosed by cytologic examination of cerebrospinal fluid and should be considered in the prognosis of Arnold-Chiari malformation and selection of cases for treatment.