|LETTER TO EDITOR
|Year : 2022 | Volume
| Issue : 2 | Page : 114-115
Ultrasonography diagnosis of acrania–exencephaly sequence at 22 weeks gestation
Department of Radiology, St. John's Hospital, Bengaluru, Karnataka, India
|Date of Web Publication||10-Jan-2023|
Dr. Ravikanth Reddy
Department of Radiology, St. John's Hospital, Bengaluru - 560 034, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Reddy R. Ultrasonography diagnosis of acrania–exencephaly sequence at 22 weeks gestation. Muller J Med Sci Res 2022;13:114-5
To the Editor-in-Chief,
A 30-year-old primigravida from a rural background presented to the hospital at 22 weeks of gestation and was referred for anomaly scan. The patient is from low-socioeconomic stratum and has not been compliant with folic acid supplementation during pregnancy. Ultrasonography revealed fetal movements and fetal heart sounds. However, fetal parameters such as biparietal diameter and head circumference could not be ascertained as the calvarium was not appreciated on ultrasonography. There was a mantle of brain tissue seen floating within the amniotic fluid [Figure 1]. Abdominal circumference and femur length were within normal limits. The amniotic fluid index was increased. An ultrasonography diagnosis of acrania–exencephaly sequence was made, and the parents were offered counseling regarding the same. The fetus was therapeutically aborted. Acrania is congenital condition of the calvarium not related to neural tube defects. Moreover, acrania is a component of acrania–exencephaly–anencephaly sequence which is an extremely rare malformation identified on antenatal scans after 10 weeks of gestation and has an incidence rate of 4–6 in 10,000 live births. Acrania which is the first stage in the sequence of events leading to anencephaly gradually shows the progression from acrania to exencephaly and from exencephaly to anencephaly. During the early stages of brain development, exencephaly is characterized by disorganized mantle of cerebral tissue noted above the level of orbits. Nevertheless, further progression to anencephaly is characterized by failure of neural tube to close at the level of the forebrain and midbrain. However, normal fusion is noted at the level of the hindbrain and cervical cord region. Acrania–Exencephaly is characterized by typical imaging findings on ultrasonography such as absent calvarium with increased echogenicity of the amniotic fluid; bilobular face which is named as "Mickey-Mouse" sign; and "Beret" sign which represents overhanging mantle of cerebral tissue. Congenital hypophosphatasia and Osteogenesis imperfecta have been implicated as causes of poor mineralization of the calvarium and must be differentiated from acrania. Genetic and syndromic associations encompassing aneuploidy and extracranial malformations have been linked with acrania–exencephaly–anencephaly sequence.
|Figure 1: Longitudinal ultrasonography image demonstrating mantle of brain tissue floating in the amniotic fluid suggesting acrania-exencephaly sequence. Note the absent calvarium|
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Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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