Perinatal Rapid Enlargement of Suprasellar-Prepontine Arachnoid Cyst: Report of Case and Literature Review.

Arachnoid cysts are benign developmental anomalies representing 1% of all intracranial lesions. Suprasellar prepontine location of arachnoid cyst in the perinatal period has been reported in the perinatal period with the advent of prenatal imaging. A rare case of rapidly enlarging suprasellar prepontine arachnoid cyst diagnosed at 28 weeks on routine antenatal ultrasonographic and magnetic resonance imaging is presented. Rapid enlargement of the cyst near term led to endoscopic fenestration of the cyst and ventriculocystocisternostomy followed by ventriculoperitoneal shunt in the postnatal life. Serial imaging in the perinatal period led to early intervention with good postnatal outcome. We also review all cases of prenatal suprasellar prepontine arachnoid cyst mentioned in literature and discuss the management strategies.

INTRODUCTION

Arachnoid cysts in the perinatal period are benign developmental anomalies representing 1% of all intracranial lesions.[12] Congenital or primary arachnoid cysts occur due to splitting or duplication of the arachnoid membrane with fluid content similar to cerebrospinal fluid (CSF).[34] Secondary arachnoid cysts occur following hemorrhage, trauma, infection, and usually, communicate with the subarachnoid space.[2] These cysts usually occur along the surface of the brain mainly at the sylvian and Rolandic fissure. Suprasellar location of arachnoid cyst in the prenatal period has been reported in few cases. We present a case of rapid enlargement of suprasellar prepontine arachnoid cyst resulting in hydrocephalus in the perinatal period. The suprasellar prepontine cyst was diagnosed incidentally on routine sonographic examination in the antenatal period. Endoscopic fenestration of the cyst and ventriculocystocisternostomy followed by ventriculoperitoneal shunt in the early postnatal life resulted in the good outcome.

CASE REPORT

A 1-day term neonate was referred to the pediatric neurosurgical unit in view of large head size. The mother had undergone elective cesarean section at term in view of large head size of the baby. Antenatal history of the mother was uneventful till about 28 weeks. A routine sonographic examination of the fetus done at 28 weeks revealed hypoechoic lesion in the suprasellar space with lack of color Doppler signals. The fetal biometry was normal. Fetal 1.5 T magnetic resonance imaging (MRI) of the brain done at 29 weeks revealed a cyst in the suprasellar-prepontine region measuring 1.8 cm × 1.7 cm × 1.5 cm. The signal intensities of cyst fluid-matched signal intensities of CSF on T1-weighted images, T2-weighted images, and fluid-attenuated inversion recovery sequences. The MRI imaging features were suggestive of suprasellar prepontine arachnoid cyst [Figure 1]. The lateral ventricles were mildly dilated. There was no occlusion of the foramen of Monro or aqueduct of sylvius. No other associated intracranial abnormality was detected. The fetus was monitored on a weekly basis by serial sonographic examination till term. Fetal sonographic examination done at 39 weeks revealed significant increase in size of suprasellar prepontine arachnoid cyst with compression of third ventricle resulting in dilation of lateral ventricles. A neonate was delivered by elective cesarean section at 39 weeks with Apgar scores of 8 and 9 at 1 and 5 min, respectively. The head circumference was above 95 percentile at birth. MRI of the brain performed on day 1 of birth revealed a large arachnoid cyst measuring 5.8 cm × 5.6 cm × 5.1 cm in the suprasellar– prepontine cistern [Figure 2]. The cyst was displacing the chiasma and floor of the third ventricle upward occluding the foramen of Monro. The cerebral peduncle was splayed apart, and the midbrain was displaced posteriorly occluding the aqueduct of sylvius. This resulted in obstructive hydrocephalus [Figure 2]. Endoscopic fenestration of the cyst along with ventriculocystocisternostomy was performed. The basilar artery in the prepontine space was seen through the endoscope. Follow-up computed tomogrpahy scan done on day 18 showed persistent hydrocephalus [Figure 3a]. A ventriculoperitoneal shunt through the frontal burr hole was performed to reduce the hydrocephalus [Figure 3b]. Histology of the cyst wall showed to be of fibrous connective tissue with no epithelial or glial lining. Karyotyping of the neonate was normal. The infant development was normal at 6 months with no recurrence of the cyst on imaging.

Figure 1

Axial T2-weighted (a) and sagittal T2-weighted magnetic resonance imaging (b) done at 29 weeks gestational age revealed a cyst in the suprasellar-prepontine region measuring 1.8 cm × 1.7 cm × 1.5 cm. (a) The lateral ventricles were mildly dilated. There was no occlusion of the foramen of Monro (a) or aqueduct of sylvius (b)

Figure 2

Magnetic resonance imaging of the brain performed on day 1 postnatally revealed a suprasellar prepontine cyst measuring 5.8 cm × 5.6 cm × 5.1 cm. The signal intensities of cyst fluid-matched signal intensities of cerebrospinal fluid on all sequences. (a, b and c) The cyst was displacing the floor of the third ventricle upward occluding the foramen of Monro. (a, b and d) The brainstem was stretched and displaced posteriorly occluding the aqueduct of sylvius resulting in obstructive hydrocephalus

Figure 3

(a) Computed tomography of the brain revealed persistent hydrocephalus. (b) Ventriculoperitoneal shunt was placed through the right frontal burr hole

DISCUSSION

Arachnoid cysts are rare congenital benign developmental anomalies of the central nervous system.[4] The cysts are collection of CSF originating as a result of abnormal splitting or duplication of arachnoid membrane.[5] Arachnoid cysts account for only 1% of all intracranial space-occupying lesions in newborns and children.[1245] The cysts are most often detected incidentally in the supratentorial location either within the middle cranial fossa or sylvian fissure.[4] Suprasellar location of arachnoid cyst is uncommon representing only 10% of all intracranial arachnoid cyst.[67]

Arachnoid cysts, though are considered congenital, the diagnosis is often made during childhood after the symptoms appear.[6] Cyst enlargement leads to hydrocephalus, visual impairment, precocious puberty, hormone deficiency, ataxia, tremors, and head bobbing.[8910] Prenatal diagnosis of intracranial arachnoid cysts was rarely reported.[9] However, in the last decade, with the advent of better antenatal diagnostic facilities such as sonography and fetal MRI prenatal diagnosis of arachnoid cysts is being increasingly done before the onset of manifestation.[234911] Most of the arachnoid cysts are now diagnosed in the second trimester, infact as early as 20 weeks of gestational period.[15] It is now suggested that suprasellar arachnoid cyst arise in prepontine space and extend upward in the suprasellar cistern. Hence, the term suprasellar prepontine arachnoid cyst is preferred.[7]

Suprasellar-prepontine arachnoid cysts in the prenatal period can occur in isolation with no other intracranial abnormalities.[6] However, cysts located in the suprasellar region can occur in association with hydrocephalus,[26812] agenesis of corpus callosum, and rarely hypothalamic hamartoma.[13] Some suggest that the association of these cysts with hydrocephalus is part of common maldevelopment. Others suggest that cyst enlargement results in occlusion of foramen of Monro superiorly or aqueduct of sylvius posteriorly leading to the development of obstructive hydrocephalus.[2] In fact, obstructive hydrocephalus occurs in 90% of patients with suprasellar arachnoid cyst.[2]

Perinatally diagnosed suprasellar prepontine arachnoid cyst may remain clinically silent in postnatal period[14] or regress spontaneously.[715] They have propensity to enlarge rapidly in size during the second or third trimester[123] or even in postnatal period[9] and manifest with signs and symptoms of hydrocephalus, endocrine dysfunction, and visual impairment. Several interesting theories have been postulated for rapid cyst enlargement.[210] The ball valve hypothesis suggests that the slit-like valve allows one-way pulsatile movement of CSF from the subarachnoid space into the cyst. The fluid outflow from the cyst is prevented by this one-way valve leading to cyst enlargement.[23910] Another theory suggests that cyst enlargement occurs due to the presence of osmotic gradient between the cyst contents and subarachnoid space.[10] This theory is not supported in congenital cyst as cyst content is similar to CSF. Another theory which has strong validation is that enlargement of cyst occurs due to secretory nature of cells lining the cyst wall.[310] However, the most accepted theory especially in cases of prepontine suprasellar arachnoid cyst is that this one way slit valve is created by piercing of the basilar artery through the arachnoidal leaflets of Liliquests membrane.[1617] The valve opening increases due to caudal-to-cephalad CSF flow during the cardiac cycle. The valve opening decreases during the remainder of cardiac cycle as cephalad to caudal CSF flow pushes the slit opening against the basilar artery.[16] Although the growth potential of the cyst varies from fetus to fetus, serial prenatal imaging is necessary to follow the cyst growth.[12] Table 1 demonstrates all cases of prenatally diagnosed suprasellar prepontine arachnoid cyst.[12356891214]

Table 1

Demonstrates all cases of prenatally diagnosed suprasellar prepontine arachnoid cysts

Management strategy of perinatal suprasellar prepontine arachnoid cyst is highly controversial. Some clinicians recommend treating only those cyst causing symptoms.[6812] Others recommend treating even asymptomatic cysts to avoid future complications.[11] Management strategies include cystoperitoneal shunt or either endoscopic/microscopic fenestration of the cyst and cystocisternostomy or cystoventriculostomy[51112] or ventriculocystocisternostomy.[17] Endoscopic ventriculocystocisternostomy is considered much superior to ventriculocystostomy.[17] Fujimara et al. reported a case of 3 cm suprasellar arachnoid cyst diagnosed at 25 weeks gestational age. Enlargement in cyst size at 5 months postnatally lead to endoscopic cystoventriculostomy. The patient had normal development at 3 years of age.[6] Nakamura et al. performed a two-stage surgery for a huge prepontine suprasellar arachnoid cyst in a neonate-cystoperitonal shunt was performed followed by endoscopic cystoventriculostomy.[9] De Keersmaecker at et al. in a series of 12 prenatally diagnosed arachnoid cysts reported seven patients with suprasellar arachnoid cysts. Only two patients underwent endoscopic fenestration of the cyst in early postnatal life. Five patients had normal development on follow-up. Only one patient who underwent endoscopic fenestration of cyst at day 4 for large suprasellar arachnoid cyst developed autism at age 5. Pregnancy was terminated in only one fetus at 21 weeks who had developed bilateral ventriculomegaly.[5]

Perinatal outcome in fetal arachnoid cyst depends on brain integrity rather than cyst location or size.[5] The outcome is better in absence of other developmental anomalies and in presence of normal karyotype.[1]

In the present case rapid enlargement of the cyst probably occurred due to CSF influx from the arachnoid slit valve located at the point of penetration of basilar artery. Appropriate surgical therapy in the postnatal period in absence of any other intracranial anomalies and normal karyotype led to a good outcome.

CONCLUSION

Rapid enlargement of incidentally diagnosed prenatal suprasellar prepontine arachnoid cyst can occur in perinatal period. Serial evaluation by imaging-either ultrasonography or MRI in the perinatal period is necessary to demonstrate this rapid cyst enlargement. Appropriate surgical therapy in the postnatal period in the absence of any other intracranial anomalies and normal karyotype led to a good outcome.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.