Arachnoid cyst found in fetal ultrasound: A case report

Arachnoid cysts are rare, fluid-filled cavities within the arachnoid membrane of the central nervous system. While typically asymptomatic in postnatal cases, their prenatal detection on ultrasound poses diagnostic and prognostic challenges. We report a case of a fetus diagnosed with an arachnoid cyst during routine second-trimester ultrasound. High-resolution ultrasound and fetal MRI confirmed the presence of an isolated, noncompressive arachnoid cyst. Genetic testing, including karyotyping, and serological evaluations revealed no chromosomal abnormalities or associated structural anomalies. This case underscores the importance of accurate prenatal imaging and multidisciplinary care. Isolated arachnoid cysts generally carry a favorable prognosis, yet regular monitoring is essential to detect potential complications. Management includes detailed prenatal counseling, delivery planning, and postnatal evaluation to assess the need for surgical intervention. Prenatal diagnosis of arachnoid cysts facilitates early counseling and comprehensive management planning. Further research is needed to enhance diagnostic accuracy and optimize management protocols for these rare lesions.