EP05.56: Prenatal diagnosis of arachnoid cysts: MRI features; does it add to routine antenatal ultrasound?

24 fetuses, sonographically diagnosed to have arachnoid cysts on routine ante-natal US. MRI was done during the same week of ultrasound examination. Out of the 24 cases 18(75%) were supratentorial while 6 (25%) were located at the posterior fossa. 18/ 24 (75%) cases MRI confirmed the same diagnosis of US without adding extra-finding. MRI added extra-finding in 4/24 (16.666%) as follows: 1 case diagnosed by US to have a posterior fossa arachnoid cysts; MRI added the presence of a small posterior parietal meningocele; US diagnosed supra-tentorial arachnoid cyst and corpus callosum agenesis; MRI confirmed this diagnosis and added the presence of vermian hypoplasia denoting Dandy Walker malformation as well as pachygyria; US diagnosed infratentorial arachnoid cyst; MRI added the presence bilateral multi-cystic dysplastic kidneys changing the diagnosis to Meckel's Gruber syndrome; US diagnosed supra-tentorial arachnoid cyst; MRI detected its precise its location at the right ambient cistern with consequent brain stem compression. 2/24 (8.333%); only MRI gave the right diagnosis. US diagnosed a case to have a posterior fossa arachnoid cyst (false positive); MRI changed the diagnoses to mega cisterna magna; the other case US showed multi-locular cystic lesion which MRI diagnosed as multi-locular interhemispheric cyst. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.