Gene analysis of L1 neural cell adhesion molecule in prenatal diagnosis of hydrocephalus.

X-linked hydrocephalus is the most common form of inherited hydrocephalus, and is associated with severe neurological deficits and premature death. We have shown that mutations in the gene encoding L1 neural cell adhesion molecule result in X-linked hydrocephalus, which enables improved prenatal diagnosis and investigation of the role of this molecule in sporadic cases. Here we report two pedigrees with apparently sporadic hydrocephalus in which we demonstrated a disabling mutation in the L1 gene. This enabled us to provide definitive prenatal diagnosis at 10 weeks' gestation.