PRENATAL DIAGNOSIS OF ARACHNOID CYSTS

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1 REVIEW ARTICLE PRENATAL DIAGNOSIS OF ARACHNOID CYSTS Chih-Ping Chen* Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, and Department of Biotechnology, Asia University, Taichung, Taiwan. SUMMARY 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. [Taiwan J Obstet Gynecol 2007;46(3): ] Key Words: arachnoid cysts, MRI, prenatal diagnosis, ultrasound Introduction Arachnoid cysts are a rare central nervous system malformation, representing only 1% of all intracranial masses in newborns [1]. 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 [2]. Secondary (acquired) arachnoid cysts result from hemorrhage, trauma, and infection and usually communicate with the subarachnoid space [1,3]. 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 [4]. Arachnoid cysts *Correspondence to: Dr Chih-Ping Chen, Department of Obstetrics and Gynecology, Mackay Memorial Hospital, 92, Section 2, Chung-Shan North Road, Taipei 104, Taiwan. cpc_mmh@yahoo.com Accepted: June 28, 2007 may be associated with ventriculomegaly and dysgenesis of corpus callosum [5]. Prenatal ultrasound and magnetic resonance imaging (MRI) have led to the increased diagnosis of central nervous system abnormalities of the fetuses (Figures 1 8: page , cases 1 3). Prenatal Diagnosis Fetal arachnoid cysts can be evaluated prenatally by ultrasound and/or MRI [5 21]. To date, at least 27 cases of fetal arachnoid cysts have been reported (Table). Among these, 9 cases had prenatal MRI evaluation in addition to ultrasound. The arachnoid cyst can appear as a hypoechoic lesion on prenatal ultrasound. Most of fetal arachnoid cysts were first diagnosed in the third trimester. In a few cases, the diagnosis was made in the second trimester. Bretelle et al [18] reported the first-trimester diagnosis of a posterior fossa arachnoid cyst at 13 gestational weeks by transvaginal sonographic examination. The majority of arachnoid cysts are supratentorial with sylvian fissure cysts being Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 187

2 C.P. Chen Table. Reported cases of fetal arachnoid cysts diagnosed by ultrasound and/or magnetic resonance imaging (MRI) GW at Authors prenatal Sonographic Location [Reference] sonographic findings diagnosis GW at Prenatal MRI prenatal MRI findings in Perinatal outcome diagnosis addition to cyst Diakoumakis et al [6] Suprasellar 32 A 3.5 cm suprasellar cystic Vaginal delivery at 37 weeks, 2,654 g, mass a 4.3 cm suprasellar arachnoid cyst 35 A 4 cm suprasellar arachnoid with hydrocephalus, a solitary seizure cyst with hydrocephalus at age 3 days, a cystoperitoneal shunt at age 19 days Meizner et al [7] Parieto-occipital 22 A cm cystic mass in Vaginal delivery at 39 weeks, 3,400 g, the right parieto-occipital lobe a 6 7 cm arachnoid cyst, no of the brain, no hydrocephalus hydrocephalus, no deficit or seizures, 38 Enlargement of the cyst up to lost to follow-up 5 4cm Raman et al [8] Posterior fossa 24 A cm posterior cranial Cesarean section at 38 weeks, 3,500 g, fossa cyst, dilation of the third a posterior fossa arachnoid cyst, ventricle ventriculomegaly, cystoperitoneal and ventriculoperitoneal shunts, recurrent seizures, death at age 2.5 months Langer et al [9] Case 1 Supratentorial, 25 A cm anechoic Vaginal delivery at 40 weeks, 3,620 g, middle cranial supratentorial mass within the an arachnoid cyst in the middle cranial fossa right parieto-occipital lobe fossa and right parieto-occipital lobe, 28 A slight increase in the diameter hydrocephalus, a cystoperitoneal of the cyst (4 cm), shunt at age 2 months, normal no ventriculomegaly development at age 18 months Case 2 Supratentorial, 32 A 6 cm supratentorial arachnoid Cesarean section at 40 weeks, 3,080 g, midline cyst in the midline, a suprasellar arachnoid cyst, mild ventricular dilation ventricular dilation, cystoperitoneal and ventriculoperitoneal shunts at age 8 days, normal development at age 20 days 188 Taiwan J Obstet Gynecol September 2007 Vol 46 No 3

3 Arachnoid Cysts Hogge et al [10] Posterior fossa A 1 1 cm cystic structure in Termination of pregnancy, the left posterior fossa, a prominent nose, micrognathia, compressing the right overlapping of the fingers, a thincerebellar hemisphere walled cyst compressing the right cerebellar hemisphere, a karyotype of 46,X, der(x)t(x;9)(q22;q22)mat with partial trisomy 9q and partial monosomy Xq at amniocentesis Hassan et al [11] Case 2 Midline 17 Bilateral ventriculomegaly, Termination of pregnancy at 24 weeks, a midline cystic structure in 886 g, a midline arachnoid cyst, the anterior half of the brain ventriculomegaly, no associated measuring cm malformations, a karyotype of 24 Progressive increase of the 46,XY at amniocentesis cystic size and worsening ventriculomegaly Pilu et al [12] Case 1 Midline and the 23 A large midline cyst in the Cases 1 3: One termination of anterior-middle anterior-middle third of brain, pregnancy, two delivered at term: third of brain agenesis of corpus callosum a cystoperitoneal shunt in both, Case 2 As in Case 1 32 As in Case 1 normal development at ages 6 and Case 3 As in Case 1 22 As in Case 1 9 years Case 4 Midline and the 28 A large midline cyst in posterior Cases 4 5: Delivery at term, posterior third third of brain a cystoperitoneal shunt in one case, of brain normal development at ages 2 and Case 5 As in Case 4 28 As in Case 4 7 years Case 6 Ambient cistern 22 A small cyst in ambient cistern, Termination of pregnancy, trisomy double-outlet right ventricle, 18 at prenatal diagnosis clenched hands Case 7 Ambient cistern 34 A small cyst in ambient cistern, Delivery at term, seizures, developmental agenesis of corpus callosum delay at age 4 years (continued on next page) Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 189

4 C.P. Chen Table. (continued) GW at Authors prenatal Sonographic Location [Reference] sonographic findings diagnosis GW at Prenatal MRI prenatal MRI findings in Perinatal outcome diagnosis addition to cyst Rafferty et al [13] Middle cranial 33 Macrocephaly, right Cesarean section at 39 weeks, fossa ventriculomegaly, a 5 cm an endoscopic fenestration of the middle cranial fossa cyst on day 1, normal development arachnoid cyst at age 6 months Levine et al [14] Case 1 22 An arachnoid cyst Partial agenesis 31 of corpus callosum with absent body and splenium Case 2 Midline 20 A midline arachnoid cyst Normal corpus callosum that was not visualized by sonography Case 3 26 A large arachnoid cyst Extent of mass 27 effect on 33 surrounding 36 structures Elbers and Furness [15] Supratentorial 18.5 A large midline arachnoid cyst Cesarean section at 38 weeks, normal 30 Decrease of the cyst size development at age 2 years 32 Complete resolution of the cyst Blaicher et al [5] Case 1 Left-temporal, 39 A cm hypoechoic 39 A perisylvian Elective cesarean section, 3,495 g, perisylvian homogeneous lesion in the arachnoid cyst no neurological abnormality, normal left parietal hemisphere with no development at age 6 months compression of surrounding structures Case 2 Third ventricle cm asymmetric 34 Callosal Cesarean section at 39 weeks, 3,300 g, 190 Taiwan J Obstet Gynecol September 2007 Vol 46 No 3

5 Arachnoid Cysts hypoechoic homogeneous dysgenesis, repeated apneas and generalized lesion in the third ventricle normal falx seizures, anticonvulsive therapy with separating the basal ganglia, cerebri, cortical phenytoin, slightly abnormal mild bilateral dilation of pattern, development at age 5 months with the posterior horns cerebellum, diminished head control and reduced basal ganglia visual fixation and brain stem Golash et al [16] Suprasellar 17 A 2.5 cm midline cystic lesion 28 Slight dilation Elective cesarean section at 38 weeks, 24 Cyst size 3.2 cm of the occipital ventriculomegaly and macrocephaly, 28 Cyst size 3.2 cm horns of the endoscopic cystoventriculostomy lateral and cystocisternostomy, normal ventricles development at age 2 years Nakamura et al [17] Prepontine- 28 Macrocephaly, enlarged 28 A supra and Vaginal delivery at 35 weeks, suprasellar ventricles and a midline infratentorial implementation of a cyst-peritoneal cystic lesion fossae cyst shunt on day 18, endoscopic compressing cystoventriculostomy at age the brain stem 2 months, a 1-month delay of development at age 4 months Bretelle et al [18] Posterior fossa 13 An anechoic mass above the Termination at 15 weeks, 103 g, posterior fossa and between karyotype 46,XY, a posterior median the two occipital lobes arachnoid cyst, no other anomalies Souter et al [19] Case 2 Midline 25 Tetralogy of Fallot Cesarean section at 37 weeks, 1,961 g, 34 IUGR, a cm midline facial dysmorphism, inguinal hernias, intracranial arachnoid cyst, tetralogy of Fallot with a large posterior and superior to overriding aorta, MRI confirmed the thalami a cm midline arachnoid cyst, marked global developmental delay at age 13 months, a postnatal karyotype of 46,XY,der(14)t(14;20) (q32.2;p13) with a subtelomeric deletion of the distal long arm of chromosome 14. (continued on next page) Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 191

6 C.P. Chen Table. (continued) GW at Authors prenatal Sonographic Location [Reference] sonographic findings diagnosis GW at Prenatal MRI prenatal MRI findings in Perinatal outcome diagnosis addition to cyst Kusaka et al [20] Quadrigeminal 30 An anechoic mass in the 31 No obliteration Normal vaginal delivery, no cistern quadrigeminal cistern of the cerebral hydrocephalus at age 1 year without hydrocephalus aqueduct, no communication between the ventricular system and the cyst Fujimura et al [21] Suprasellar 25 A 3-cm midline cystic lesion, 28 Confirmation of Vaginal delivery at 37 weeks, 2,844 g, no ventriculomegaly a suprasellar endoscopic cystoventriculostomy at arachnoid cyst age 5 months, normal development at age 3 years GW = gestational weeks; = no information; IUGR = intrauterine growth restriction. 192 Taiwan J Obstet Gynecol September 2007 Vol 46 No 3

7 Arachnoid Cysts the most common. Arachnoid cysts may progressively enlarge in utero, causing ventriculomegaly. Elbers and Furness [15] reported an unusual case of presumed arachnoid cyst diagnosed at 18.5 weeks gestation. The cyst resolved at 32 weeks gestation. Serial prenatal sonographic examinations are able to assess the size of the cyst and the ventricles. Prenatal MRI helps to demonstrate the anatomic details of other central nervous system abnormalities, such as compression of the aqueduct, communication between the cyst and the ventricles, and corpus callosum dysgenesis. Figure 1. Prenatal ultrasound of an arachnoid cyst of case 1. Prenatal ultrasound at 32 weeks gestation revealed a cm midline interhemispheric hypoechoic homogeneous lesion. Magnetic resonance imaging (MRI) at 33 gestational weeks showed a left interhemispheric arachnoid cyst, marked dysgenesis of the corpus callosum, and colpocephaly. The karyotype was 46,XY. A 2,788-g male baby was delivered at 37 weeks gestation. Postnatal MRI confirmed the prenatal diagnosis. A cystoperitoneal shunt was performed at age 7 months. The infant was doing well at age 1 year and 2 months. Differential Diagnosis Prenatal diagnosis of intracranial hypoechoic cystic lesions should include a differential diagnosis of arachnoid cysts, porencephalic cysts, glioependymal cysts, choroid plexus cysts, aneurysms of the vein of Galen, schizencephaly, cystic neoplasms, and intracranial hemorrhage [12]. A B C Figure 2. (A) Sagittal, (B) axial and (C) coronal views of magnetic resonance imaging of case 1 at 33 weeks gestation. Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 193

8 C.P. Chen A B Figure 3. (A) Sagittal and (B) axial views of postnatal magnetic resonance imaging of case 1 at age 3 days. fibrous walls. Glioependymal cysts may have a mass effect and are often associated with agenesis of the corpus callosum. Choroid plexus cysts Choroid plexus cysts, unilateral or bilateral, are frequently detected in the second trimester. Choroid plexus cysts are sonolucent cysts within the choroids plexus of the lateral ventricle. Large choroid plexus cysts may be associated with trisomy 18. Figure 4. Prenatal ultrasound of an arachnoid cyst of case 2. Prenatal ultrasound of case 2 at 31 weeks gestation revealed a cm left interhemispheric hypoechoic homogeneous lesion. Magnetic resonance imaging (MRI) at 32 weeks gestation showed a left interhemispheric arachnoid cyst and colpocephaly. A 2,620-g male baby was delivered at term. Postnatal MRI confirmed the prenatal diagnosis. The size of the arachnoid cyst was measured about cm. There was a left-to-right midline shift. A cystoperitoneal shunt was performed at age 8 months. The child was doing well at age of 3 years and 4 months. Porencephalic cysts Porencephalic cysts are usually unilateral and communicate with the ventricular system with a cavity lined with white matter. Porencephalic cysts result from infarction of the brain secondary to vascular insults, trauma, infection, hemorrhage, or monochorionic monozygotic twin twin transfusion. In contrast, arachnoid cysts are usually asymmetric and smooth-walled; they do not communicate with the ventricular system and have a mass effect. Glioependymal cysts Glioependymal cysts are usually multilocular and located within the brain parenchyma. Glioependymal cysts have an ependymal lining, whereas, arachnoid cysts have Aneurysms of the vein of Galen Aneurysms of the vein of Galen are vascular anomalies of the vein of Galen located in the brain deeply and posteriorly to the thalami and in the subarachnoid space. Color Doppler is helpful for the diagnosis of aneurysms of the vein of Galen. Prenatal sonographic detection of fluid-filled lesions in the posterior third of the brain, which are found in association with hydrops fetalis, ventriculomegaly, porencephaly, single umbilical artery, chorioangioma or limb reduction defects, should raise the suspicion of aneurysms of the vein of Galen. Schizencephaly Schizencephaly or true porencephaly is characterized by unilateral, asymmetric or bilateral congenital fullthickness clefts of the cerebral mantle. Schizencephaly may or may not communicate with the ventricular system and are lined by gray matter. Schizencephaly can be associated with ventriculomegaly, polymicrogyria, heterotopias, agenesis of the corpus callosum, absent septum pellucidum, and optic nerve hypoplasia. Cystic neoplasms Cystic neoplasms, such as cystic teratoma and cystic astrocytoma, consist of solid and irregular cystic components and have a mass effect. 194 Taiwan J Obstet Gynecol September 2007 Vol 46 No 3

9 Arachnoid Cysts A B C Figure 5. (A) Sagittal, (B) axial and (C) coronal views of magnetic resonance imaging of case 2 at 32 weeks gestation. Intracranial hemorrhage Intracranial hemorrhage usually occurs in the subependymal germinal matrix region and is associated with hypoxia, platelet disorders, coagulopathy, alterations in cerebral blood pressure in the case of twin twin transfusion or demise of a monozygotic co-twin, fetomaternal hemorrhage, and maternal medications. Intracranial hemorrhage may initially present echogenic blood clots in the ventricles and subsequently lead to ventricular dilation. Chromosomal Abnormalities Associated with Congenital Arachnoid Cysts Fetal arachnoid cysts can be associated with chromosomal abnormalities. Therefore, prenatal diagnosis of an arachnoid cyst, especially in association with structural abnormalities, should prompt a cytogenetic investigation. Various associated chromosomal abnormalities have been reported. For instance, Hogge et al [10] reported partial trisomy 9q (9q22 qter) and partial monosomy Xq (Xq22 qter) in a fetus with an infratentorial arachnoid cyst. The fetus postnatally manifested a prominent nose, micrognathia, overlapping of the fingers, and a thin-walled cyst compressing the right cerebellar hemisphere. Souter et al [19] reported a subtelomeric deletion of the distal long arm of chromosome 14, i.e. monosomy 14q (14q32.3 qter), in a fetus with tetralogy of Fallot, intrauterine growth restriction, and a midline intracranial arachnoid cyst. The infant postnatally manifested facial dysmorphism, inguinal hernias, tetralogy of Fallot, a midline arachnoid cyst, and marked global developmental delay. Pilu et al [12] reported trisomy 18 in a fetus with a small arachnoid cyst in the ambient cistern, a double-outlet right ventricle, and clenched hands. Elbers and Furness [15] additionally reported their experience of the association of triploidy with a fetus with an arachnoid cyst. Fetal Outcome The prognosis of fetal arachnoid cysts is dependent on the presence or absence of the corpus callosum, the presence or absence of other congenital malformations, parenchymal hemorrhages, the rate of the growth of the cyst, and progression of ventriculomegaly. Fetal Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 195

10 C.P. Chen A B C Figure 6. (A) Sagittal, (B) axial and (C) coronal views of postnatal magnetic resonance imaging of case 2. Figure 7. Prenatal ultrasound of an arachnoid cyst of case 3. Prenatal ultrasound of case 3 at 23 weeks gestation revealed a cm midline interhemispheric hypoechoic homogeneous lesion. The karyotype was 46,XY. Magnetic resonance imaging (MRI) at 24 weeks gestation showed an interhemispheric arachnoid cyst and dysgenesis of the corpus callosum. Progression of the cyst was noted in late gestation. A 2,350-g male baby was delivered prematurely at 28 weeks gestation. Postnatal MRI confirmed the prenatal diagnosis. A cystoperitoneal shunt was performed at age of 1 week. The child was doing well at age 4 years. arachnoid cysts without associated structural anomalies or chromosomal abnormalities can have a favorable outcome. In some cases with rapid progression of the lesion and ventriculomegaly, appropriate pediatric surgical therapy may be required in early infancy. Currently, postnatal endoscopic cystoventriculostomy and cystocisternostomy have become less invasive surgical alternatives [16,17,21]. The prognosis of fetal intracranial cysts has been shown to rely on the brain integrity rather than the cyst volume or location [22]. Therefore, in order to establish the correct prognosis and intellectual outcome of fetuses with arachnoid cysts, MRI is an important adjunct to ultrasound and helps to optimize neonatal management by accurate determination of the fetal anatomy and objective perinatal counseling. Conclusion This article provides a thorough review of fetal arachnoid cysts, including prenatal diagnosis, differential diagnosis and associated chromosomal abnormalities, as well as 196 Taiwan J Obstet Gynecol September 2007 Vol 46 No 3

11 Arachnoid Cysts A B C Figure 8. (A) Sagittal, (B) axial, and (C) coronal views of magnetic resonance imaging of case 3 at 24 weeks gestation. 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. References 1. Robinson RG. Congenital cysts of the brain: arachnoid malformations. Prog Neurol Surg 1971;4: Pascual-Castroviejo I, Roche MC, Martinez Bermejo A, Arcas J, Garcia Blazquez M. Primary intracranial arachnoidal cysts: a study of 67 childhood cases. Childs Nerv Syst 1991;7: Oliver LC. Primary arachnoid cysts: report of two cases. Br Med J 1958;1: Wester K. Peculiarities of intracranial arachnoid cysts: location, sidedness, and sex distribution in 126 consecutive patients. Neurosurgery 1999;45: 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: Diakoumakis EE, Weinberg B, Mollin J. Prenatal sonographic diagnosis of a suprasellar arachnoid cyst. J Ultrasound Med 1986;5: Meizner I, Barki Y, Tadmor R, Katz M. In utero ultrasonic detection of fetal arachnoid cyst. J Clin Ultrasound 1988;16: Raman S, Rachagan SP, Lim CT. Prenatal diagnosis of a posterior fossa cyst. J Clin Ultrasound 1991;19: Langer B, Haddad J, Favre R, Frigue V, Schlaeder G. Fetal arachnoid cyst: report of two cases. Ultrasound Obstet Gynecol 1994;4: Hogge WA, Schnatterly P, Ferguson JE 2nd. Early prenatal diagnosis of an infratentorial arachnoid cyst: association with an unbalanced translocation. Prenat Diagn 1995;15: Hassan J, Sepulveda W, Teixeira J, Cox PM. Glioependymal and arachnoid cysts: unusual causes of early ventriculomegaly in utero. Prenat Diagn 1996;16: Pilu G, Falco P, Perolo A, Sandri F, Cocchi G, Ancora G, Bovicelli L. Differential diagnosis and outcome of fetal intracranial hypoechoic lesions: report of 21 cases. Ultrasound Obstet Gynecol 1997;9: Rafferty PG, Britton J, Penna L, Ville Y. Prenatal diagnosis of a large fetal arachnoid cyst. Ultrasound Obstet Gynecol 1998; 12: Levine D, Barnes PD, Madsen JR, Abbott J, Mehta T, Edelman RR. Central nervous system abnormalities assessed with prenatal magnetic resonance imaging. Obstet Gynecol 1999;94: Elbers SEL, Furness ME. Resolution of presumed arachnoid cyst in utero. Ultrasound Obstet Gynecol 1999;14: Taiwan J Obstet Gynecol September 2007 Vol 46 No 3 197

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