Background

Acalvaria is a rare congenital abnormality with clinical features of soft, lax skull as a result of absent skull bones and associated muscles. It's usually a fatal anomaly with unclear pathogenesis.

Case Presentation

A full-term female baby delivered via spontaneous delivery was referred to our hospital with a large anterior fontanelle measuring 6.5x7cm. Antenatal record suggested a normal prenatal ultrasound with no other pregnancy complications. The skull and face appeared normal on inspection with healthy skin cover. On palpation, frontal and parietal bones were absent in the upper part. The rest of physical examination was unremarkable. Cranial ultrasound revealed an open metopic suture. Head CT scan confirmed these bony defects with normal brain structure and ventricular system. She was managed conservatively and scheduled to have a repeated CT at 6 months. On follow up at 5 months of age, she has normal weight and length with head circumference of 38 cm (microcephaly). Denver developmental screening test II suspected delay in gross motor area. Referral was made to rehabilitation department and another screening is due in 2 weeks. Reconstructive surgery is arranged in the next future.

Discussion

Acalvaria is an extremely rare congenital malformation characterized by the absence of cranial bone, dura mater, and associated muscles. Antenatal diagnosis is a requisite to allow for appropriate counseling and management. Surviving infants can be managed conservatively then scheduled for surgical reconstruction in the later age. The living case of this anomaly was reported to have severe developmental delay with metal retardation.