Chiari II malformation and occult spinal dysraphism. Case reports and a review of the literature.

We report two cases of children with occult spinal dysraphism who were also found to have many associated brain anomalies seen in the Chiari II malformation. No previous report has commented on the possible association between the Chiari II malformation and the 'closed' form of neural tube defect. One child had symptoms referable to pathology at the craniocervical junction. Neither child had cutaneous stigmata associated with occult spinal dysraphism over the caudal midline spine. These cases, although seemingly rare, lend support to the theories that the association between the Chiari II malformation and patients with myelomeningoceles is due to dysgenesis of the rostral and caudal neural tube. These cases are also important as refutation of earlier theories that link these two entities by proposing that the Chiari II malformation is due to overdrainage of cerebrospinal fluid at the site of myelomeningocele.