The estimated incidence is at ~1:1000 pregnancies 4.
Pathology
The condition is thought to result from abnormal migration of mesenchymal tissue, which normally covers the cerebral hemispheres. The calvarial bones are partially or entirely absent, with relative (albeit abnormal) preservation of cerebral hemisphere development. A thin membrane surrounds the cerebral hemispheres.
Radiographic features
Ultrasound
As the ossification of the fetal cranium begins and accelerates after nine weeks, antenatal ultrasound allows diagnosis from 11 weeks onwards. Looking specifically for frontal bone ossification in the axial and coronal planes is important.
1. Mannes E, Crelin E, Hobbins J, Viscomi G, Alcebo L. Sonographic Demonstration of Fetal Acrania. AJR Am J Roentgenol. 1982;139(1):181-2. doi:10.2214/ajr.139.1.181 - Pubmed
2. Ekici E & Gülmezoglu A. Sonographic Diagnosis of Fetal Acrania. J Clin Ultrasound. 1991;19(6):363-6. doi:10.1002/jcu.1870190608 - Pubmed
3. Fong K, Toi A, Salem S et al. Detection of Fetal Structural Abnormalities with US During Early Pregnancy. Radiographics. 2004;24(1):157-74. doi:10.1148/rg.241035027 - Pubmed
4. Yildirim H, Koç M, Kurt N, Artaş H, Aygün D. Neonate with Meroacrania: Radiological Findings and Review of the Literature. Diagn Interv Radiol. 2009;15(4):232-5. doi:10.4261/1305-3825.DIR.1075-07.1 - Pubmed
5. Bianca S, Ingegnosi C, Auditore S et al. Prenatal and Postnatal Findings of Acrania. Arch Gynecol Obstet. 2005;271(3):256-8. doi:10.1007/s00404-004-0621-2 - Pubmed
6. Cincore V, Ninios A, Pavlik J, Hsu C. Prenatal Diagnosis of Acrania Associated with Amniotic Band Syndrome. Obstet Gynecol. 2003;102(5 Pt 2):1176-8. doi:10.1016/s0029-7844(03)00118-2 - Pubmed
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