EP01.10: Prenatal diagnosis and prognosis of fetal arachnoid cysts

Abstract

Objectives:To explore the clinical significance of the prenatal diagnosis of fetal arachnoid cysts by ultrasonography and to evaluate the prognosis. Methods: We retrospectively analysed the follow-up data of 60 fetuses deemed as having arachnoid cysts by prenatal ultrasonography. The data were obtained via serial ultrasonography, prenatal and/or postnatal magnetic resonance imaging (MRI), or postmortem examination. For those live births, the developmental quotient (DQ) scores were determined by the Gesell Developmental Scale. Results:The diagnosis of 30 fetuses were made in the second and third trimesters, respectively. Fifty-one of the lesions were located in the supratentorial compartment, and nine were in the posterior fossa. Twenty-four lesions were isolated, while the others were associated with intracranial and/or extra central nervous system (CNS) malformations. The outcomes were spontaneous resolution, progression, induced abortion, infant mortality, intrauterine death, and live birth with normal neurodevelopment or mental retardation. Two cases were lost to follow-up. The accuracy rate of prenatal ultrasonography was 86.21% (50/58). Conclusions: Prenatal ultrasonography is the modality of choice for the diagnosis of fetal arachnoid cysts. Serial ultrasonography is important in monitoring the status of cysts. Moreover, prenatal MRI is a valuable complementary tool. For live births, the prognosis appears to be good. Congenital arachnoid cysts are an accumulation of cerebrospinal fluid between the dura and the cerebral cortex. They appear as hypoechoic lesions on prenatal ultrasound, most frequently on the surface of the brain or in the main cerebral fissures. We report a case of arachnoid cyst in a 28 y.o G1P0 woman who was referred for a fetal intracerebral cystic formation at 35 weeks. An ultrasound in our tertiary care centre at 36 weeks of gestation described a 60mm inter-hemispheric and temporal arachnoid cyst. A fetal MRI confirmed the diagnosis and the arachnoid cyst measured 58x64mm and was located in the suprasellar space and in the left temporal fossa. A unilateral ventriculomegaly and a posterior shift of the cerebral stem were associated, but the gyration was normal and there were no signs of hemorrhage. The biparietal diameter measured 93 mm, corresponding to the 97th centile for gestational age. An elective Caesarean section was planned at 39 weeks because of the increased head circumference but was done earlier at 38 weeks after premature rupture of membranes. The baby boy weighted 3000g and Apgar score was 9-9-9. No neonatal resuscitation was needed. Cardiorespiratory monitoring was performed in the first 24 hours of life in case of apnea or desaturation episodes. The newborn's physical and ophthalmologic examinations were normal, with no sign of increased intracranial pressure. Head perimeter was 35.5 cm. Neurologic evaluation suggested good prognosis as fetal outcome does not correlate to the cyst's size when isolated. Arachnoid cysts can potentially cause neurological deficit by compres...