Isolated Acrania in the Presence of Amniotic Band Syndrome

Acrania is an extremely rare congenital developmental anomaly. It is often confused with another disease entity, anencephaly. Even though these two developmental defects often occur simultaneously, they are believed to have different pathogenic mechanisms. We report the case of a 22-year-old woman with an unremarkable first trimester pregnancy who delivered a demised male fetus at 16 weeks gestation. External and microscopic examination of the fetus revealed normal development in all internal organs. The brain was covered by leptomeninges only, with an absence of skull and overlying skin. Additionally, both the fetus and placenta showed evidence of amniotic band syndrome. A diagnosis of isolated acrania in the presence of amniotic band syndrome was made.

The exact etiology of acrania is not well understood. Two popular theories suggest that amniotic bands or a migration failure of the ectodermal mesenchyme may play a role in the pathogenesis. We believe that isolated acrania may represent a group of developmental anomalies which share a common ultimate outcome: absence of the neurocranium with relatively minor effects on brain development.