Fetal Arachnoid Cysts: Their Site, Progress, Prognosis and Differential Diagnosis

Abstract

Arachnoid cysts are lined by arachnoid membranes and filled with cerebrospinal fluid. Etiologically, they are thought to be due to maldevelopment of the arachnoid or secondary to trauma or infection. Postnatally, many are asymptomatic and remain quiescent for years, although others expand and cause symptoms by compressing adjacent brain and/or expanding the overlying skull. Being congenital, it should be possible to identify them in the fetus, and this has proved to be so. But are they anatomically similar and do they behave the same as those detected postnatally? Fifteen fetuses with fluid-filled cysts were identified from the database of the Fetal Management Unit at St. Mary's Hospital in Manchester. Five were diagnosed at or before 20 weeks of gestation, 4 between 21 and 30 weeks, and 6 at 31 weeks or more. Thirteen cysts were in the supratentorial compartment, and 2 in the posterior fossa. Eleven fetuses were delivered, and 4 pregnancies were terminated. One of the born children had Pallister-Hall syndrome and died on day 19, and another had Aicardi's syndrome, is retarded and has fits, 1 with a posterior fossa cyst developed hydrocephalus in utero and was delivered early for the insertion of a ventriculoperitoneal shunt, he is moderately mentally delayed. Of the remaining 8 children, 1 has been lost to follow-up, and 7 appear to be reaching their early milestones on time. The 4 terminated fetuses had a postmortem examination, 2 did not have arachnoid cysts; 1 had an expanding glioependymal cyst which had destroyed most of the cerebral hemispheres, and the other had a sagittal sinus thrombosis with extensive cavitation of one cerebral hemisphere. The diagnosis of an arachnoid cyst in the fetus can be difficult and may be confused with other fluid-filled cysts.

Outcome of 12 antenatally diagnosed fetal arachnoid cysts: Case series and review of the literature

“…22 In another postnatal report (n ¼ 11) the size of most of the cysts stabilized in utero (76%) or postnatally (52.2%). 27 Diagnosis of arachnoid cysts in our series was made in 25% of the cases in the second trimester while the remaining 75% were diagnosed between 28 and 34 weeks of gestation. In the literature 22/36 (62%) of fetal cysts were diagnosed in the second trimester and 14/36 (38%) in the third trimester.…”

“…Chromosomal abnormality Other features Hogge et al 10 Partial trisomy 9q and partial monosomy Xq Prominent Nose, micrognatia, overlapping fingers, thin wall cyst compressing the right cerebral hemisphere Souter et al 19 Monosomy 14q Tetralogy of Fallot, IUGR, midline intracranial arachnoid cyst Pilu et al 12 Trisomy 18 Small arachnoid cyst in the ambient cistern, double outlet right ventricle, clenched hands Chen et al 24 Trisomy 18 Microcephaly, hypogenesis of cerebellar vermis, syndactyly, VSD, rocker-bottom feet Stein et al 25 Trisomy 20 mosaicism Arachnoid cyst of the basal cistern Bannister et al 27 Pallister-Hall, Aicardia Napolitano et al 34 Seckle syndrome Microcephaly, hypotelorism, beaked nose, micrognathia Kau et al 43 Chudley-Mc Cullough syndrome Martinez-Lage et al 44 Neurofibromatosis type 1 e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y 1 9 ( 2 0 1 5 ) 1 1 4 e1 2 1…”

Prenatal and Postnatal Follow-Up of a Fetal Interhemispheric Arachnoid Cyst with Partial Corpus Callosum Agenesis, Asymmetric Ventriculomegaly and Localized Polymicrogyria

“…One of them, with partial ACC, lissencephaly and atrioventricular septal defect died in utero [10] and 3 others (Bannister et al [11] , Pilu et al [12] ) with complete ACC led to a termination of pregnancy. Thereby, neurological follow-up was available for only 51 live-born children.…”

Intracranial Arachnoid Cysts

“…MRI is also adequate to evaluate the compression of cysts on neural structures. 1,33,34 The indications for surgery and the type of surgical treatment are still matters of debate. 1,2,4,10,30 On MRI, however, the combination of extra-axial location, morphologic features, and signal intensity matching that of CSF allows one to make the diagnosis of an uncomplicated AC with confidence.…”