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Articles » Central nervous system » Arachnoid cyst
2012-02-05-12 Arachnid cyst © Grochal

Arachnoid cyst

Frantisek Grochal, MD

Femicare, s.r.o., Center of prenatal ultrasonographic diagnostics, Martin, Slovak republic. UVN SNP Ruzomberok, Gynecological and obstetrical department. Catholic University in Ruzomberok, Faculty of Health Care, Ruzomberok, Slovak Republic.

(Edited by Frantisek Grochal)

Case report

A 28-year-old woman (G1P0) with non-contributive history was sent to our office at 31st week of gestational age due to cystic structure within the fetal brain.

Our examination found interhemispheric arachnoid cyst. No other anomalies were noticed during our examination. The newborn was delivered in term via cesarean secion and was diagnosed to have ectodermal dysplasia. Additionally syndactyly of the third and fourth finger of the right hand and cleft of the lower lip and dorsal palate were found in the newborn. The neonate also suffers from deafness.

Retrospectively we were able to find an inconspicuous defect of the lower lip in our stored 3D images and not very obvious defect of the hard palate which we missed during our exam. 

This case is a big lesson for me. Sometime we pay too much attention to a striking dominant finding and we miss  those less conspicuous, but often very important anomalies that can lead us to more appropriate and serious diagnosis. Although the management would stay the same in this case, there are other diagnoses, where it wouldn't be the same (especially when the diagnosis is postulated earlier in pregnancy).

Images 1, 2, and 3: 31 weeks of gestational age; the images show transverse (images 1, 2) and coronal (image 3) scans of the fetal head with biloculate arachnoid cyst (the smaller part of the biloculate cyst is measured on the image 2).


Images 4, 5, 6, 7, 8, 9, and 10: 31 weeks of gestational age; 3D images of the fetal head showing the arachnoid cyst in several 3D modalities (HDlive imaging - images 1-4; classical 3D imaging using the minimal mode - image 8; 3D niche-mode imaging - image 9; and isolated volumetric appearance of the arachnoid cyst with the volume of 11.86 cm3 - image 10).




Images 11, 12, 13, 14, 15, and 16: 31 weeks of gestational age; 3D images of the fetal face. The images 11-14 shows "normal" appearance of the fetal lips. Angulation of our stored 3D images discovered an inconspicuous cleft of the lower lip of the fetus (arrows on the images 15 and 16), which was originally missed during the patient's scanning.




Images 17, 18, and 19: 31 weeks of gestational age; 2D scans of the fetal face. Although these planes are not very appropriate for thorough assessment of the hard palate, retrospective analysis of our images found inhomogeneity in the hard palate concordant with the cleft that was found in the newborn.


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