Interhemispheric arachnoid cyst associated with meningomyelocele: a case report

Objective

To present a prenatally diagnosed case of interhemispheric arachnoid cyst associated with lumbosacral meningomyelocele and discussion of management for this case.

Case(s)

A 26-year-old gravida 1, para 0 patient was referred to our unit at 24 weeks gestation. A detailed ultrasound scan revealed a 21x21 mm interhemispheric arachnoid cyst and lumbosacral meningomyelocele. After counseling, termination of pregnancy was offered and accepted. The diagnosis was confirmed by postmortem examination.   

Conclusion

The presence of other anomalies should be investigated for the management of arachnoid cyst.

Keywords

Interhemispheric arachnoid cyst, meningomyelocele, management

Introduction

Arachnoid cysts are cystic cavities filled with a fluid like cerebrospinal fluid and including collagen and cell within arachnoid membrane, and they comprise 1% of intracranial lesions. Arachnoid cysts may exist in any part of central nervous system including spinal canal. They are usually located on supratentorial and midline.[1,2] They rarely associated with other anomalies.
In this report, we discussed the diagnosis and management of arachnoid cyst case associated with meningomyelocele that we prenatally diagnosed.

Case(s)

Fetal biometric measurements of twenty-six years old, gravida 0, parity 0 patient without follow-up were found consistent with 24 weeks, having normal amniotic fluid, placenta posterior located and with normal appearance in the routine fetal ultrasonographic examination performed on 24 weeks gestation. In the cranium examination, 21x21 mm hypoechoic cystic mass with normal margins is located at axial section, interhemispheric and even subthalamic level during the cranium examination (Fig. 1). No blood flow was observed in cystic mass during Doppler ultrasonographic examination. Posterior lateral ventricle was measured as 8.7 mm, cerebellum as 24 mm and cistern magna as 2 mm. Also, cavum septum pellucidum was observed but no corpus callosum was seen positionally. In the columna vertebralis examination, 43x31 mm meningomyelocele was found in lumbosacral area (Fig. 2).
No additional anomaly was found in other system examinations of fetus. Anomalies were confirmed by fetal MRI (Fig. 3) and corpus callosum agenesia was ruled out. The family was informed about fetus and termination of pregnancy after karyotype analysis was offered to the family as an option. The result of karyotype analysis was 46 XY and in the pathological examination of fetus, 25x25 mm cystic mass and 50 mm lumbosacral meningomyelocele were found on supratentorial region in middle interhemispheric area. It was reported that hyperplastic arachnoid cells were observed in the microscopic analysis of the cyst and antenatal diagnosis was confirmed.

Discussion

Arachnoid cysts comprise 1% of intracranial lesions. They appear as congenital (primary) or associated with bleeding, trauma and infection (secondary). Congenital ones appear between 6 and 8 weeks gestation during hemispheric folding and arachnoid membrane separation. More than 50% of arachnoid cysts are located middle fossa in supratentorial region. Other intense localizations are major fissures (silvian, rolandic and interhemispheric), surfaces of cerebral hemispheres, sella turcica region and anterior fossa.[1-4]
In our case, interhemispeheric located arachnoid cyst at 24 weeks gestation was presented. Most of the arachnoid cyst cases were diagnosed at the end of second trimester.[5] The earliest diagnosis of arachnoid cyst was reported by Bretelle et al. at 13 weeks gestation  by transvaginal ultrasonography.[1]
The differential diagnosis should be done for arachnoid cyst by porencephalic cyst which may be in intracranial hypoechoic lesion appearance, glioependimal cyst, choroid plexus cyst, vein of Galen aneurysm, schizencephaly, cystic neoplasm and intracranial hemorrhage.[6] Arachnoid cysts are seen as hypoechoic cystic mass which has regular margins in ultrasonography and no blood flow in Doppler examination.[6,7] MRI can be beneficial for both differential diagnosis and scanning accompanying anomalies.[8] Arachnoid cyst is usually isolated and seems to be associated with ventriculomegaly and corpus callosum agenesis.[5,6,8]
In our case, arachnoid cyst seems associated with meningomyelocele but association was not found in the literature. Akdemir et al.[9] and Gedikbaşı et al.[10] reported that arachnoid cyst grows as gestational week increases and they may cause ventriculomegaly. Pilu et al. reported associated corpus callosum agenesis in two of seven arachnoid cyst cases (great arachnoid cyst case on midline located on anterior fossa and two arachnoid cyst cases which are 5 mm and 6 mm in ambient cistern).[6] In the case presented by Elbers and Furness, they diagnosed arachnoid cyst at 18.5 weeks gestation, and they reported that cyst regressed at 32 weeks gestation and then disappeared.[11]
Karyotype is normal in most of the arachnoid cyst cases, but karyotyping analysis is recommended in isolated cases. Pilu et al. found trisomy 18 in karyotype analysis of an arachnoid cyst case located in ambient cistern associated with right ventricle with double outlet and nodular hand diagnoses.[6] Hoge et al. reported the association of infratentorial arachnoid cyst case with partial trisomy 9q (9q22_qter) and partial monosomy Xq (Xq22_qter) (12). Souter et al. found monosomy 14q (14q32.3_qter) in midline intracranial arachnoid cyst case accompanied with fallot's tetralogy and intrauterine growth.[13]

Conclusion

For the management of arachnoid cyst cases, presence of all other anomalies that may accompany should be researched. Karyotype analysis and termination of pregnancy may be recommended in the presence of multiple anomalies. Prognosis is good in isolated cases, but they should be followed up in terms of cyst size and obstructive ventriculomegaly.

References

1. Bretelle F, Senat MV, Bernard JP, Hillion Y, Ville Y. First-trimester diagnosis of fetal arachnoid cyst: prenatal implication. Ultrasound Obstet Gynecol 2002;20:400-2.
2. Chen CP. Prenatal diagnosis of arachnoid cysts. Taiwan J Obstet Gynecol 2007;46:187-98.
3. Choi JU, Kim DS. Pathogenesis of arachnoid cyst: congenital or traumatic? Pediatr Neurosurg 1998;29:260-6.
4. Wester K. Peculiarities of intracranial arachnoid cysts: location, sidedness, and sex distribution in 126 consecutive patients. Neurosurgery 1999;45:775-9.
5. Langer B, Haddad J, Favre R, Frigue V, Schlaeder G. Fetal arachnoid cyst: report of two cases. Ultrasound Obstet Gynecol 1994;4:68-72.
6. Pilu G, Falco P, Perolo A, Sandri F, Cocchi G, Ancora G, et al. Differential diagnosis and outcome of fetal intracranial hypoechoic lesions: report of 21 cases. Ultrasound Obstet Gynecol 1997;9:229-36.
7. Barjot P, von Theobald P, Refanhi N, Delautre V, Herlicoviez M. Diagnosis of arachnoid cysts on prenatal ultrasound. Fetal Diagn Ther 1999;14:306-9.
8. Blaicher W, Prayer D, Kuhle S, Deutinger J, Bernaschek G. Combined prenatal ultrasound and magnetic resonance imaging in two fetuses with suspected arachnoid cysts. Ultrasound Obstet Gynecol 2001;18:166-8.
9. Akdemir N, Altunyurt S, Uysal D, Yüceer N. Fetal intrakraniyal kistik görünümlü kitle saptanan iki olgu: tanı, takip ve prognoz. Turkiye Klinikleri Journal of Gynecology and Obstetrics 2009;19:231-5.
10. Gedikbasi A, Palabiyik F, Oztarhan A, Yildirim G, Eren C, Ozyurt SS, et al. Prenatal diagnosis of a suprasellar arachnoid cyst with 2- and 3-dimensional sonography and fetal magnetic resonance imaging: difficulties in management and review of the literature. J Ultrasound Med 2010;29:1487-93.
11. Elbers SE, Furness ME. Resolution of presumed arachnoid cyst in utero. Ultrasound Obstet Gynecol 1999;14:353–5.
12. Hogge WA, Schnatterly P, Ferguson JE 2nd. Early prenatal diagnosis of an infratentorial arachnoid cyst: association with an unbalanced translocation. Prenat Diagn 1995;15:186-8.
13. Souter VL, Glass IA, Chapman DB, Raff ML, Parisi MA, Opheim KE, et al. Multiple fetal anomalies associated with subtle subtelomeric chromosomal rearrangements. Ultrasound Obstet Gynecol 2003;21:609-15.

	File/Dsecription
	Fig. 1. The appearance of interhemispheric arachnoid cyst on axial plane.
	Fig. 2. The appearance of meningomyelocele on axial plane.
	Fig. 3. The appearance of interhemispheric arachnoid cyst on axial plane by MRI.