Sonographic diagnosis and prognosis of fetal arachnoid cysts.

Purpose: To explore the clinical significance of sonographic (US) diagnosis of fetal arachnoid cysts and to evaluate their prognosis.

Methods: Sixty fetuses deemed to have arachnoid cysts by prenatal US were included in this study. Data from serial US, prenatal and/or postnatal MRI, or post-mortem examinations were retrospectively analyzed. For live births, the developmental quotient scores were determined using the Gesell Developmental Scale.

Results: Thirty fetuses were diagnosed during the second trimester and another 30 fetuses were diagnosed in the third trimester. Fifty-one lesions were located in the supratentorial compartment, and 9 were located in the posterior fossa. Twenty-four lesions were isolated, and the remaining lesions were associated with intracranial and/or extra central nervous system malformations. The evolution of the cysts included progression, stability, or spontaneous resolution. The outcomes included induced abortion, intrauterine death, live birth with either normal neurodevelopment or mental retardation, and infant mortality. Two cases were lost to follow-up. The accuracy of prenatal US diagnosis was 86.2% (50/58).

Conclusion: Prenatal US is the modality of choice for the diagnosis of fetal arachnoid cysts. Serial US examinations are critical to monitor the lesions. Moreover, prenatal MRI is a valuable complementary tool. For live births, the prognosis appears to be good.