Chiari type 1 malformation in an infant with type 2 Pfeiffer syndrome: further evidence of acquired pathogenesis.

There seems to be an association between type 1 Chiari malformation (CM) and some congenital craniosynostosis syndromes. Type 2 Pfeiffer syndrome is a condition associated with premature fusion of multiple cranial sutures, cloverleaf skull (kleeblatschädel deformity), prominent ptosis, thumb and first toe abnormalities, variable syndactyly, and mutated genes for type 1 or 2 fibroblast growth factor receptor. These children generally do poorly because of significant often severe neurologic and cognitive defects, and many die very young. Roughly half of all patients with Pfeiffer syndrome, and virtually all with type 2 disease, also have type 1 CM. Chiari malformation may not be congenital but acquired as a consequence of the skull deformities and other associated intracranial factors in patients with craniosynostosis. We report a term male infant with type 2 Pfeiffer syndrome, who was not noted to have any CM on initial brain imaging done at 2 months but in whom repeated imaging demonstrated clear evidence of CM by 4 months, despite reconstructive craniotomies and unilateral ventriculoperitoneal shunt insertion. Posterior fossa decompression yielded a good result. This patient provides further evidence to support the concept of acquired tonsillar herniation in patients with craniosynostosis syndromes. The etiology seems multifactorial and related to (1) the disproportionately slow growth of the skull relative to the brain, particularly in the posterior fossa, secondary to early fusion of skull sutures, in turn secondary to congenital deficiencies in fibroblast growth factor receptors; (2) impaired venous sinus drainage; (3) hydrocephalus; and (4) resultant elevations in intracranial pressure.