Acalvaria is an extremely rare congenital anomaly with very few cases reported in literature till date. Acalvaria is characterized by absent flat bones of the cranial vault with normal base of skull, facial bones and cranial contents [1]. The pathogenesis of this congenital abnormality is unknown and is described as fatal anomaly. Herein, we report a living case of acalvaria with normal brain development.

Figure 1. Radiograph showing absent parietal bones with normal facial bones.

A new born infant male, product of non-consanguineous marriage was born preterm at 28 weeks of gestation due to premature rupture of membranes, mother was a booked antenatal case and prenatal checkups including ultrasound were normal. His birth weight was 1.6 Kg. He was found to have boggy swelling over the cranium. Rest of the general physical and systemic examination was normal. Radiograph of skull (Figure 1) showed absent parietal bones with normal facial bones and CT head (Figure 2) showed normal intracranial structures with no ventricular dilatation and absent parietal bones.

Figure 2. Computed tomography (axial view) showing absent parietal bones with normal facial bones

Calvarium was reconstructed using collagen sheath application and plaster of Paris (POP) cast cap at the age of 02 months and conservative supportive care was given. Spontaneous scalp bones growth was seen resulting in partial closure of the defect. He had normal milestones, growth velocity and good scholastic performance. He was last reviewed at the age of 6 and half years (Fig 3). He demonstrated normal growth and brain development and X–ray of head revealed partial closure of defect owing to bony growth (Fig 4). He is planned for cranioplasty subsequently.

Figure 3. Lateral profile picture of the patient at 6½ years of age.

Acalvaria is a rare congenital anomaly characterized by absent flat bones of the cranial vault with normal base of skull, facial bones and cranial contents [1]. Although the intracranial contents are reported to be normal, there can be some neuropathological abnormalities [2]. The prevalence of this condition is thought to be less than 1 per 100,000 births. Other congenital anomalies like facial cleft, micropolygyria, holoprosencephaly, hydrocephalus, club foot etc. have been reported in association with acalvaria [3, 4]. This malformation has been described as a fatal anomaly [5]. Only few live cases in the world have been reported in literature and these cases are severely mentally retarded and disabled. In our case, there is no other associated congenital abnormalities and brain development and functioning is normal in this child possibly following early aggressive management including calvarial reconstruction using collagen and POP cap.

Figure 4. Radiograph lateral view showing partial bone growth with residual defect.

The etiology and pathogenesis of this congenital anomaly remains unknown. Some investigators still consider acalvaria to be a part of spectrum of anencephaly. However, the presumed pathogenesis is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but intact layer of skin over the brain parenchyma [1, 6]. Acalvaria can be secondary to amniotic band syndrome, neural tube defect, or use of angiotensin converting enzyme inhibitors during pregnancy [7]. In our present case, no secondary cause could be elucidated.

The condition is diagnosed postnatally by presence of soft, lax skin over scalp with absence of flat bones and muscles with normal facial bones. As this condition is fatal malformation, timely antenatal diagnosis using vigilant transvaginal ultrasound scan demonstrating normal cerebral hemispheres, around 12 weeks of gestation can accurately diagnose acalvaria in most of the cases [8]. Other craniofacial anomalies including anencephaly, hydrocephalus, hypophoshatasia, osteogenesis imperfecta, etc. need to be differentiated from this condition. In acalvaria, alfa-fetoprotein level is usually elevated, and unconjugated estrogen is usually undetectable [1, 2].

The initial management is mainly conservative aimed at supportive care and management of any associated congenital anomalies [2]. Spontaneous bone growth has been seen in some newborns with scalp defects such as in cutis aplasia, highlighting the importance of conservative management. The patients can subsequently undergo skull reconstruction by bone grafting and cranioplasty at school going age [9]. In our case, the child was initially managed with calvarium reconstruction using collagen sheath application and plaster of paris (POP) cast cap, spontaneous growth of the bones has occcured filling the defect partially. Now child is being planned for cranioplasty.

Dr. Pawan Dhull, Department of Neurology, Command Hospital (Air Force), Bangalore, Karnataka, India and Dr Saroj K Patnaik, Department of Pediatrics, Army Hospital (RR), Delhi, India recommend this article for publication.