Introduction. Acrania is a very rare lethal congenital malformation characterized by an absence of the cranial vault with developed cerebral hemispheres. It is sometimes confused with anencephaly in which both the forebrain and neurocranium are not developed. Although these two conditions principally differ in their morphology and pathogenesis, acrania may be a precursor of the development of anencephaly through the process known as Acrania-exencephaly-anencephaly sequence.
Case report. A 27-year-old woman was diagnosed to have a viable fetus with an absent skull vault and uncovered brain directly exposed to amniotic cavity. A diagnosis of acrania was made. A medical abortion was performed in the 14^th week of pregnancy. A gross examination of the formalin-fixed fetus revealed a complete absence of the calva and brain tissue. The cranial structures stop abruptly above the orbits and the fetus showed a triangular face with bulging eyes. At the top of the head, a huge defect with a residual thin covering membrane was visible. According to the gross morphology and in correlation with previous ultrasound findings, the pathologist established the diagnosis of secondary anencephaly.
Conclusion. This paper suggests that many of the reported anencephaly cases that are diagnosed during the second or third trimester of pregnancy might represent the end of a spectrum that initially appears as isolated acrania. This may be the reason for much higher global incidence of anencephaly compared to acrania.   

Keywords: acrania, exencephaly, anencephaly, acalvaria

  

Corresponding author:

Vladimír Bartoš

e-mail: vladim.bartos@gmail.com