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Intra-fourth ventricular arachnoid cyst: The case for a direct surgical approach
Soumen Kanjilal1, Ved Prakash Maurya1, Kuntal Kanti Das1, Pawan K Verma1, Awadhesh Kumar Jaiswal1, Lily Pal2, Sanjay Behari1
1 Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), Lucknow, Uttar Pradesh, India
2 Department of Pathology, Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), Lucknow, Uttar Pradesh, India
|Date of Submission||07-May-2021|
|Date of Decision||20-Jun-2021|
|Date of Acceptance||04-Jun-2021|
|Date of Web Publication||07-Jan-2022|
Kuntal Kanti Das,
Department of Neurosurgery, First Floor, C-Block (Hospital Building), Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), Raebareli Road, Lucknow 226014, Uttar Pradesh.
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Arachnoid cysts (ACs) are benign, extra-axial, developmental cysts derived from the arachnoid membrane. These cysts often develop in the cisternal spaces and rarely involve the fourth ventricle. When they do, their differential diagnosis can be challenging. Although their surgical treatment has to be proactive, there appears to be a lack of consensus regarding the best surgical strategy. Here we report a 16-year-old boy with hydrocephalus and ataxia in the setting of a fourth ventricular AC. A direct surgical approach through a midline suboccipital corridor enabled us to sub totally resect the cyst and establish the cerebrospinal fluid (CSF) pathway. The child had an uneventful recovery and continues to be asymptomatic at 1-year follow-up. We conclude that a direct approach to the cyst appears to be a reasonable treatment choice and primary CSF diversion rarely helps in these situations. We present a literature review and a management algorithm.
Keywords: Histopathology, hydrocephalus, marsupialization, midline suboccipital, recurrence
| Introduction|| |
Arachnoid cysts (ACs) are benign, cerebrospinal fluid (CSF) containing, extra-axial, congenital, non-neoplastic arachnoidal anomalies, accounting for only approximately 1.1% of intracranial lesions. Most commonly, ACs are located in or adjacent to the sylvian fissure and in the cerebellopontine angle. Intraventricular location is rare. ACs in the fourth ventricle are particularly uncommon. To date, only a few reports of fourth ventricular ACs have been published [Table 1].,,,,,,,,,,,,,,, Apart from their rarity, there is a lot of doubt regarding the best way of their management, the various options being ventriculoperitoneal shunt placement, complete or partial cyst removal either through an open approach or an endoscopic approach with or without endoscopic third ventriculostomy. Herein, we report a case of fourth ventricular AC in a 16-year-old boy and his successful management using a cyst marsupialization through a midline suboccipital approach without installation of any shunt. We review the literature on this topic, particularly with an attempt to chalk out a management recommendation for the neurosurgical community.
|Table 1: Summary of the 24 cases of fourth ventricular AC reported so far|
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| Case Details|| |
A 16-year-old boy presented with a headache accompanied by vomiting and blurring of vision in the left eye for 6 months. He was a diagnosed case of Coat’s disease of the right eye with an accompanying loss of vision in the same eye. He was also a known hypertensive.
On complete neurological examination, the patient was noted to have slight ataxia and a rightward shift on tandem walking with Grade I papilledema on fundoscopy. There was no evidence of any cognitive deficit.
Cranial magnetic resonance imaging (MRI) showed a cystic dilatation of the fourth ventricle. The brainstem was pushed anteriorly with compression of the prepontine cistern. There was dilatation of bilateral lateral ventricles and third ventricle with prominence of the temporal horns. There was posterosuperior displacement of the cerebellar vermis. The cyst wall showed no contrast enhancement. The cyst contained fluid with CSF-like intensity and showing suppression on FLAIR sequence and so a diagnosis of AC was made [Figure 1].
|Figure 1: On magnetic resonance imaging scan of the brain, a well-defined lesion (T1 hypo and T2 hyper intense) with smooth margin completely occupying the fourth ventricular cavity (A, B). The lesion has CSF intensity showing suppression on FLAIR sequence of magnetic resonance imaging (C). The sagittal cut after contrast administration shows no enhancement with compressed prepontine cistern. There is significant pontomedullary compression and posterosuperiorly elevated cerebellar vermis (D)|
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A midline suboccipital approach was taken. After durotomy, a bulging bluish cyst projected through the vallecular space. By using a telovelar approach, the cyst was defined. It was considered impossible to resect the cyst in toto and hence we decided to decompress and marsupialize the cyst. The cyst wall was adhered to the brainstem and the lower cranial nerve origins and hence we decided for a subtotal excision. The patency of aqueduct with normal directional flow of CSF was documented before ensuing a dural closure.
The child recovered well after surgery without any new neurological deficits. Histology revealed a diagnosis of AC. His ataxia and headache gradually improved. At 4 months’ follow-up, he was symptom free and MRI revealed resolution of hydrocephalus and a decompressed fourth ventricle [Figure 2].
|Figure 2: Postoperative magnetic resonance imaging scan of the brain suggests alleviation of ventriculomegaly with slit sized third ventricular cavity (A). After surgical decompression, the cerebellar folia are appreciated well with residual dilatation of the fourth ventricle (B). The sagittal cut reveals significant reduction in brainstem compression, patent CSF pathway and reappearance of cerebello-vermian structures with postoperative changes of midline suboccipital craniotomy (C)|
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| Discussion|| |
ACs are benign, congenital developmental cysts accounting for nearly 1.1% of intracranial lesions. Their most common locations include the sylvian fissure, prepontine area, and cerebellopontine area. It is hypothesized that the intraventricular ACs develop from the entrapped arachnoid membrane in the choroid plexus mesenchyme during the embryonic life. We also noticed during surgery in our patient that the AC was adhered to the choroid plexus of the fourth ventricle, further substantiating this hypothesis. ACs can remain asymptomatic or cause symptoms secondary to neural compression.
Development of AC inside the fourth ventricle is very rare and to the best of our knowledge only 24 cases have been reported so far in the literature [Table 1].,,,,,,,,,,,,,,, A quick review of the literature reveals that these cysts may cause CSF outflow obstruction causing headaches or rarely sudden deaths or there may be cerebellar/ brainstem compression related symptoms. Therefore, the propensity to cause acute neurological decompensation mandates proactive treatment in fourth ventricular ACs, unlike similar lesions elsewhere.
One of the important clinical dilemmas in such cysts is to determine preoperatively the nature of the lesion. The other common fourth ventricular cystic lesions include Dandy–Walker’s cyst, mega cisterna magna or the persistent Blake’s pouch cysts, and rarely parasitic cysts inside the fourth ventricle.[Table 2] shows their differences, including points on preoperative MRI which can differentiate them. Of note, differentiation of an intra-fourth ventricular AC may be more daunting than the more common retrocerebellar ACs.
A review of the literature reveals that there exist inconsistencies with regard to the management of these lesions. Ventriculoperitoneal shunts clearly fail to stop progression of these cysts, despite controlling the obstructive hydrocephalus.,,,,, Moreover, the nature of the lesion cannot be verified through this approach. A direct approach through a midline suboccipital corridor is most frequently used.,,,,,, This approach allows either a complete or a partial excision of the cyst with re-establishment of the CSF pathway. In addition, the nature of the lesion can be histopathologically verified through this method. More recently, endoscopic approaches through a frontal transventricular pathway have been reported.,, It allows a simultaneous performance of endoscopic third ventriculostomy and cyst fenestration. Both rigid and flexible endoscopic methods are available in the literature. However, the trans ventricular endoscopic approaches are dependent upon the presence of hydrocephalus and a patent aqueduct. Moreover, an endoscopic punch biopsy may not be easy and a pathological verification of the cyst may not be possible always. In our patient, we decided a direct surgical approach to attempt a complete excision, verify the nature of the lesion and also to address the attendant tonsillar herniation. We could ascertain that a complete resection was not possible, performed a wide marsupialization, and ensured that the CSF pathway was patent.
Cyst marsupialization is, however, not a curative treatment. The cyst can recur as documented by Hiroshima et al. Due to this notorious tendency for cyst recurrence and associated acute obstructive hydrocephalus, it is very important to follow these patients serially over many years.,,, We agree that our follow-up duration (4 months) is insufficient but we plan to follow this patient at a serial interval to monitor the cyst progression. However, many times, there will not be any recurrence. Moreover, it has been documented that many times, the cyst wall may be densely adherent to the brainstem or the adjoining vasculature and hence a total extirpation may not be possible. In the event of a recurrence, a trans ventricular endoscopy remains a reasonable option as the histology is already known and one only needs to create new cyst wall fenestrations. On the basis of the review of the literature, we present a management algorithm in [Figure 3].
|Figure 3: Figure showing algorithm for the management of fourth ventricle arachnoid cyst|
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| Conclusion|| |
Intra fourth ventricular ACs are rare and often present with hydrocephalus or cerebellar symptoms. A direct approach with cyst marsupialization is a reasonable treatment choice and primary CSF diversion rarely helps. Recurrences are not unusual and mandate a regular and long-term follow-up.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]