Acalvaria - report of a case and discussion of the literature.

Acalvaria is a rare condition indeed, defined as the absence of the flat bones of the skull, as well as the associated muscles and dura, with, in some cases, normal skull base bones and normal brain structures. It has been reported as a fatal congenital condition, because of the failure of afflicted children to survive for extended periods. There have, however, been reports of extended survival. The first report of this condition was in 1996, involving an 11-year-old child who had severe mental retardation. Since then, there have been few further reports of this condition, generally in infants.