Acalvaria

Acalvaria is a rare congenital disorder characterized by the absence of the cranial vault. This condition is distinct from anencephaly, another congenital disorder where there is a partial or complete absence of the cerebral hemispheres. In acalvaria, the cerebral hemispheres are completely formed and functional, but they are not covered by the skull or scalp.

Etiology

The exact cause of acalvaria is unknown. However, it is believed to be due to an early embryonic insult that disrupts the migration of mesenchyme to the cranial area. This disruption prevents the formation of the neurocranium, the portion of the skull that covers the brain.

Clinical Features

The most prominent feature of acalvaria is the absence of the cranial vault above the level of the orbit. The cerebral hemispheres are covered only by a thin layer of dura mater, a tough, protective membrane, and skin. Other features may include micrognathia (small jaw), cleft palate, and ocular hypertelorism (widely spaced eyes).

Diagnosis

Acalvaria can be diagnosed prenatally through ultrasound imaging. The absence of the cranial vault and the presence of cerebral hemispheres are key indicators of this condition. Postnatal diagnosis can be confirmed through computed tomography (CT) or magnetic resonance imaging (MRI).

Treatment and Prognosis

There is currently no cure for acalvaria. Treatment is supportive and focuses on managing symptoms and preventing complications. The prognosis for individuals with acalvaria is poor, with most infants not surviving beyond the neonatal period.

See Also

• Congenital disorders
• Craniosynostosis
• Anencephaly