Fetal arachnoid cyst of the quadrigeminal cistern in MRI and ultrasound

Temporal arachnoid cysts: are they congenital?

CASE REPORT

The authors report two cases of arachnoid cysts (ACs) neither detected during pregnancy nor shortly after birth when newborns underwent CT scan evaluation after birth head trauma. ACs were diagnosed at 10 months and 6 years, respectively. The first one becomes symptomatic, and the other one was incidentally found during a head trauma investigation.

DISCUSSION

These cases give support for the postnatal pathogenesis for some of the assumed congenital ACs. We collected data from the literature that supports the acquired hypothesis for ACs.

Different information by MRI compare to ultrasound in fetal intracranial space occupying lesions

PURPOSE

The purpose of this study was to evaluate the value of prenatal magnetic resonance imaging (MRI) in characterizing fetal intracranial space occupying lesions in comparison to prenatal ultrasound.

METHODS

This retrospective study included 50 fetuses (mean age 26 years, mean gestational weeks 31 + 1 GW) with intracranial space occupying lesions, suspected by prenatal screening ultrasound. T2-weighted, T1-weighted, SSFP, and diffusion-weighted sequences of the fetal brain were obtained on a 1.5 T unit. Pathology (n = 5), postmortem MRI (n = 3), or postnatal US (n = 42) was available as standard of reference.

RESULTS

The fetal MRI provided correct diagnosis in 49 cases (98%), while 35 (70%) by ultrasound, and MRI failed in 1 case (2%), while ultrasound failed in 15 cases (30%). Fetal MR and ultrasound were concordant in 35 of 50 cases (70%), completely discordant in 4 (8%), and partially discordant in 11 (22%) cases.

CONCLUSIONS

MRI could provide detailed information about the minor lesions, such as focal hemorrhage and periventricular nodules. Meanwhile, it could provide whole view of the lesion in order to delineate the surrounding anatomical structure. But there are still some limitations of its soft-tissue resolution in a case with teratoma; more effort is needed to improve the sequences.

[Imaging diagnosis of arachnoid cysts]

Arachnoid cysts are malformed lesions that contain a fluid similar to the cerebrospinal fluid, and are usually located within the arachnoidal membrane. They represent 1% of all intracranial lesions, and in recent years, with the development of radiological techniques, the clinical detectability of arachnoid cysts seems to have increased. Although the majority of diagnosed arachnoid cysts are located in the cranial cavity and especially in the Sylvian fissure, a small number are located at spinal level and they can occur extra- or intra-spinally. An analysis is carried out, detailing the various tests used for the diagnosis of both intracranial and spinal arachnoids cysts, analysing the indications of each one depending on the location of the cysts and patient age.

[Arachnoid cysts: Embriology and pathology]

There is still great controversy surrounding the origin of the arachnoid cyst. The most accepted theory in the case of congenital cysts explains how they are formed from an anomalous development of the arachnoid membrane, which is unfolded allowing the accumulation of cerebrospinal fluid inside and creating a cyst. This theory seems to explain the origin of convexity and sylvian cistern arachnoid cysts, whereas those in other locations might be due to other mechanisms. In the anatomopathological analysis, the arachnoid cyst wall can be seen as having few differences from normal, although thickened due to an increase quantity of collagenous material. A description of the embryological development of the arachnoid layer and cyst formation is presented, describing the main anatomopathological findings.

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

OBJECTIVES

To investigate the natural history, associated abnormalities and outcome of 12 fetuses with arachnoid cyst diagnosed antenatally by ultrasound and magnetic resonance imaging and to compare the outcome with cases in the literature.

METHODS

A retrospective study of all cases of antenatally detected fetal arachnoid cysts was performed in patients referred to a tertiary unit between 2007 and 2013. Associated abnormalities, pregnancy outcome and postnatal follow-up were analyzed. All papers about prenatally diagnosed arachnoid cysts, of the last 30 years, were evaluated (search terms in Pubmed: "prenatal diagnosis", "Arachnoid Cysts").

RESULTS

Fetal arachnoid cysts were diagnosed in 12 fetuses, 9 were females. The mean gestational age of diagnosis was 28 1/7 (range 19 1/7-34 2/7 weeks). A total of 9 cases were supratentorial, 3 were located in the posterior fossa. In 10 cases a fetal MRI was performed which confirmed brain compression in 4 out of 5 supratentorial arachnoid cyst. MRI did not reveal other malformations nor signs of nodular heterotopia. Only one fetus presented with additional major anomalies (bilateral ventricumomegaly of >20 mm and rhombencephalosynapsis) leading to a termination of pregnancy. Two neonates underwent endoscopic fenestration of the arachnoid cyst in the first week of life with no additional intervention in childhood. All but one (10/11) had a favorable postnatal outcome. This child suffered from visual impairment at autism was diagnosed at the age of 5. One child had a surgical correction of strabismus later in childhood. In one child the infratentorial arachnoid cyst regressed spontaneously on ultrasound and MRI in the postnatal period.

CONCLUSIONS

The majority of arachnoid cysts in this series are of benign origin and remain stable. Based on the current series and the review of the literature, in the absence of other associated anomalies and when the karyotype is normal, the postnatal overall and neurological outcome is favorable. Large suprasellar arachnoid cysts however, may cause visual impairment and endocrinological disturbances. Rarely associated cerebral or cerebellar malformations are present. Modern postnatal management of suprasellar arachnoid cyst consists of endoscopic cystoventriculostomy.

[The outcome of children presenting with a prenatally diagnosed arachnoid cyst]

AIM

Evaluate the outcome of children with prenatally diagnosed arachnoid cysts.

MATERIAL AND METHODS

Retrospective study of seventeen cases of children who were diagnosed with an arachnoid cyst during prenatal MRI between July 1994 and January 2007 and followed up for a mean 6 years and 6 months. Follow-up was based on evaluation of clinical files and contacts with the physicians who were following the children. The children were divided into three groups: group 1 normal development, group 2: minor clinical signs, normal schooling, group 3: major clinical symptoms, schooling disturbed.

RESULTS

Eight of the 17 patients included in this study underwent derivation surgery for the cyst. Eight of the 17 children were in group 1, and 3 in group 2. Four of the 6 children in group 3 had associated symptoms. Two of the children in group 3 present with a supratentorial cyst, and 4 with a cyst of the posterior fossa.

CONCLUSION

The prenatal diagnosis of a arachnoid cyst should be accompanied by a search for associated lesions. The risk of hydroencephalitis should be explained to the parents.

Prevalence and natural history of arachnoid cysts in children

OBJECT

Arachnoid cysts are a frequent finding on intracranial imaging in children. The prevalence and natural history of these cysts are not well defined. The authors studied a large consecutive series of children undergoing MR imaging to better define both the MR imaging-demonstrated prevalence and behavior of these lesions over time.

METHODS

The authors reviewed a consecutive series of 11,738 patients who were 18 years of age or younger and had undergone brain MR imaging at a single institution during an 11-year period. In the patients in whom intracranial arachnoid cysts were identified, clinical and demographic information was recorded and imaging characteristics, such as cyst size and location, were evaluated. Prevalence data were analyzed using univariate and multivariate logistic regression, linear regression, and ANOVA. All patients with sufficient data (repeat MR imaging studies as well as repeated clinical evaluation over at least 5 months) for a natural history analysis were identified. This group was assessed for any change in symptoms or imaging appearance during the follow-up interval.

RESULTS

Three hundred nine arachnoid cysts (2.6% prevalence rate) were identified. There was an increased prevalence of arachnoid cysts in males (p < 0.000001). One hundred eleven patients met all criteria for inclusion in the natural history analysis. After a mean follow-up of 3.5 years, 11 arachnoid cysts increased in size, 13 decreased, and 87 remained stable. A younger age at presentation was significantly associated with cyst enlargement (p = 0.001) and the need for surgery (p = 0.05). No patient older than 4 years of age at the time of initial diagnosis had cyst enlargement, demonstrated new symptoms, or underwent surgical treatment.

CONCLUSIONS

Arachnoid cysts are a common incidental finding on intracranial imaging in pediatric patients. An older age at the time of presentation is associated with a lack of clinical or imaging changes over time.

Prenatal diagnosis of arachnoid cysts

Arachnoid cysts are a rare central nervous system malformation, representing only 1% of all intracranial masses in newborns. Primary (congenital) arachnoid cysts are benign accumulation of clear fluid between the dura and the brain substance throughout the cerebrospinal axis in relation to the arachnoid membrane and do not communicate with the subarachnoid space. Secondary (acquired) arachnoid cysts result from hemorrhage, trauma, and infection and usually communicate with the subarachnoid space. The common locations of arachnoid cysts are the surface of the brain at the level of main brain fissures, such as sylvian, rolandic and interhemispheric fissures, sella turcica, the anterior cranial fossa, and the middle cranial fossa. Arachnoid cysts may be associated with ventriculomegaly and dysgenesis of corpus callosum. Prenatal ultrasound and magnetic resonance imaging have led to the increased diagnosis of fetal arachnoid cysts. This article provides a thorough review of fetal arachnoid cysts, including prenatal diagnosis, differential diagnosis and associated chromosomal abnormalities, as well as comprehensive illustrations of perinatal imaging findings of fetal arachnoid cysts. Prenatal diagnosis of intracranial hypoechoic lesions should include a differential diagnosis of arachnoid cysts and prompt genetic investigations.