Acalvaria

Acalvaria is an extremely rare congenital malformation characterized by the absence of the calvarial bones (the flat bones forming the skull vault), the dura mater, and associated muscles, while the brain and facial bones remain present. Unlike anencephaly, in acalvaria the cerebral hemispheres are developed, though they are typically covered only by a thin membrane or skin rather than the normal bony skull. The condition is classified under neural tube-related defects and is identified prenatally or at birth. The brain tissue, although initially formed, is exposed and vulnerable to mechanical injury and environmental damage, which leads to progressive degeneration. Acalvaria is almost invariably fatal, with most affected infants being stillborn or dying shortly after birth. The condition must be distinguished from other cranial vault defects such as anencephaly (where brain tissue is largely absent), acrania (absence of the cranial bones but with intact dura mater), and large cephaloceles. Prenatal diagnosis is possible through ultrasonography, which can reveal the absence of the calvarium with relatively preserved brain tissue. The exact etiology remains unclear; it has been proposed to result from abnormal migration of the membranous neurocranium or from early rupture of the amnion with disruption of the developing cranial vault. There is currently no curative treatment for acalvaria. Management is supportive and palliative. Genetic counseling is offered to affected families, though most reported cases have been sporadic with no clear familial recurrence pattern. Due to the rarity of the condition, research is limited, and understanding of the precise pathogenesis continues to evolve through case reports and small case series.

Common questions about Acalvaria