An Unusual First-Trimester Ultrasound Presentation of the Acrania-Anencephaly Sequence: The "Turkish Turban" Sign

Re: 'Turkish turban' sign: a rare phenotype of acrania-exencephaly-anencephaly sequence

Linked article: This Correspondence comments on Tonni et al. Click here to view the article.

'Turkish turban' sign: rare phenotype of acrania-exencephaly-anencephaly sequence

Linked article: There is a comment on this article by Demir et al. Click here to view the Correspondence.

Further insights into unusual acrania-exencephaly-anencephaly sequence caused by amniotic band – first trimester fetoscopic correlation with two- and three-dimensional ultrasound

Objectives

Antenatal detection of acrania-exencephaly-anencephaly (AEA) sequence beyond 10 completed weeks of gestation is usually straight-forward. An earlier detection and classification of the causative conditions prior to disaggregation of exposed dysplastic brain tissue remains challenging.

Case presentation

We present two- and three-dimensional ultrasound correlated with fetoscopic findings of an unusual type of neural tube defect at 11 gestational weeks caused by an amniotic constriction ring resulting in cystic degeneration of the developing skull.

Conclusions

By giving further illustrative insights into early defective brain development, this report confirms recent findings of an unusual subtype of acrania-exencephaly-anencephaly sequence suggesting early disruption of the developing brain, following an amniotic entrapment of the skull.

The etiopathogenic and morphological spectrum of anencephaly: a comprehensive review of literature

Anencephaly is a severe malformation of the central nervous system (CNS), being one of the most common types of neural tube defects. It is defined as total or partial absence of the calvarium, with absence of the brain. Anencephaly has an incidence of 1 to 5 in every 1000 births, and the mortality rate is 100% during intrauterine life or within hours or days after birth. The etiology of anencephaly remains unclear, but various maternal-related environmental and genetic risk factors have been reported, which include diabetes, obesity, exposure to different drugs or toxins, genetic polymorphisms and mutations, as well as positive family history for neural tube defects. One of the most important nutritional factors in the development of anencephaly is folate deficiency. Methylenetetrahydrofolate reductase (MTHFR) gene codes the enzyme involved in the intracellular metabolism of folic acid; the 677C-T polymorphism of this gene causes the thermolability of the enzyme and decreased enzymatic activity, which is also dependent of folate plasmatic level. Etiopathogenesis of anencephaly includes several mutations in various other genes, such as: platelet-derived growth factor receptor alpha (PDGFRA), cadherin epidermal growth factor (EGF) laminin G (LAG) seven-pass G-type receptor 1 (CELSR1), Vang-like 1 (VANGL1) and Vang-like 2 (VANGL2), the last two being involved in the process of neurulation. Screening tests include maternal serum alpha-fetoprotein level and ultrasound (US) examination. During the first trimester US screening, anencephaly is now detected in all cases, but in order to decrease the complication rate of pregnancy termination, the diagnosis should be established as soon as possible, during the pregnancy confirmation US. We conclude that given that anencephaly is a severe malformation of the CNS, morphological characterization could improve the screening by US that is mandatory in the first trimester in order to plan the best, safe and early management.