Neuroendoscopic Transventricular Approach for Cystic Craniopharyngioma

The literature is rich with many studies reporting different treatment modalities and approaches for cystic craniopharyngioma (CC), including microsurgery, neuroendoscopic transventricular approach, endoscopic transnasal surgery, stereotactic drainage, and Ommaya reservoir insertion. The goals of this manuscript are to report the successful treatment of an atypical case of CC using the neuroendoscopic transventricular approach (NTVA) as well as discuss the different surgical modalities for these tumors following a comprehensive review of the literature. Our patient is a nine-year-old female with a large CC who was managed using the NTVA. No complications or recurrence occurred over two years of follow-up. Results of our literature review showed lower recurrence and complication rates of the NTVA compared to other surgical modalities.The NTVA is potentially efficient, reliable, and safe for managing CC and cystic-dominant craniopharyngiomas, with low recurrence and complication rates compared to microsurgery and Ommaya reservoir insertion. Future randomized clinical studies comparing the various treatment modalities of CC are needed to solidify these conclusions.


Introduction
Craniopharyngiomas arise from squamous cells of Rathke's pouch. These benign tumors account for 10% of pediatric and 2-4% of intracranial brain tumors, are located in the intra-and suprasellar zones, and are classified as cystic, solid, or mixed [1]. Tumoral attachment to critical neurovascular tissue, such as the hypothalamus or pituitary, is a treatment challenge. Although endocrine dysfunction could be seen in total resections, the risk is increased in partial resections as well [2]. Total or partial surgical resection remains the treatment of choice, and radiation therapy may play a role in partial resections or recurrences. Neuroendoscopic transventricular fenestration and placement of an intracystic catheter with an Ommaya reservoir is a valid, minimally invasive technique in the management of large cystic craniopharyngiomas (CC) [3][4]. The objectives of this paper are to report the management of an atypical CC using the neuroendoscopic transventricular approach (NTVA), as well as discuss the different surgical modalities for these tumors following a review of the literature.

Case Presentation
The patient is a nine-year-old female who presented with headache, agitation, urinary frequency, and progressive visual deficits over the past two years. A large sellar and suprasellar lesion was detected on a CT scan, and a ventriculoperitoneal (VP) shunt was placed to relieve the progressive symptoms of hydrocephalus ( Figure 1). MRI solidified the initial suspicion of CC, where the lesion was hyperintense on T1-and T2-weighted images, without any significant, enhancing solid component on postcontrast T1weighted images, consistent with the high protein and cholesterol contents of CC ( Figure 2).

FIGURE 2: MRI of the brain
Brain MRI showing a diffuse hyperintense signal on axial fluid-attenuated inversion recovery (FLAIR) (A) and axial T2-weighted images (B), which is consistent with high levels of protein and cholesterol. Sagittal (C) and coronal (D) sections of postcontrast T1-weighted images reveal no significant enhancement of the solid component. All these findings support the diagnosis of cystic craniopharyngioma. The lesion extended from anterior to posterior fossa and laterally to the middle fossa, compressing and elevating all basal elements (frontal lobes, temporal lobes, third ventricle, brain stem). The chronically compressed pituitary infundibulum has been elongated and pushed superiorly as shown (arrow in C).
A few days prior to surgery and despite no signs of VP shunt failure, the patient's exam was notable for acute confusion, severe ataxia, and bilateral blindness. The NTVA was performed using a rigid neuroendoscope (Aesculap AG, Tuttlingen, Germany). The cyst was accessed through a right frontal burr hole, and the contents were drained. The neuroendoscope was advanced to the right lateral ventricle, where cyst wall calcifications were visible through the thinned and elevated neural elements. The choroid plexus was then identified and tracked back to the foramen of Monro. The cyst wall was sampled and the cyst was punctured, draining a copious gray-to-green liquid content with debris. Simultaneous irrigation with a Ringer's solution and suctioning cleared the contents of the cyst; adjacent neurovascular structures were clearly visible at the end of the procedure.
The postoperative course was uneventful, and all symptoms improved in the immediate postoperative period, except for visual loss. Histopathology confirmed the diagnosis of CC. The patient did not develop any symptoms of chemical meningitis on close follow-up. Her pituitary function remained normal postoperatively as well as on long-term follow-up. We opted not to pursue any additional surgical or adjuvant therapy due to the lack of any obvious solid tumor component on postoperative MRI, very thin residual cyst wall, and extensive basal extension with involvement of the critical structures ( Figure 3). Follow-up MRIs showed no evidence of tumor regrowth or re-accumulation of cystic contents ( Figure 4).

Discussion
In this paper, we report a child with a large CC, which was treated via NTVA only with no complications or recurrence after two years of follow-up. As there is a lack of consensus regarding the optimal surgical approach to manage CC, we conducted a literature review about the different treatment modalities and summarized our results in tables.
We found 17 reports that utilized the NTVA (with and without Ommaya reservoir insertion) for the treatment of CC in 67 patients, with a follow-up period ranging from six to 73 months; the recurrence rate ranged between nil to 54% (  The surgical modality of choice may differ depending on patient-and/or tumor-related factors. In pediatric and adult patients with good functional status, long life expectancy, and small tumor size, microsurgical gross-total resection (GTR) is the recommended strategy [3]. GTR may be considered an acceptable option for tumors not invading the hypothalamus due to the low risk of recurrence and to avoid subsequent radiotherapy. Tumors invading the pituitary stalk, however, are potentially better managed with sub-total resection (STR) due to the high risk of postoperative endocrinopathy [18]. Tumor recurrence, reaching up to 62% ( Table 2), is the main concern following microsurgery, endoscopic endonasal, and/or Ommaya reservoir insertion [15,17,. Alternatively, see Table 2 for the recurrence rate of CC managed with NTVA (without Ommaya reservoir insertion) ranged between 0% and 33% across various studies.  The NTVA is recognized as a safe, efficacious, and minimally invasive procedure for intra-and paraventricular craniopharyngiomas, especially for cystic, large, and extensive lesions [2][3]. Our literature review results, as well as our experience exemplified by the case report described above, further support this notion ( Table 1, Table 3). Intraoperative fenestration of the cyst wall usually drains the dense liquid content, typically described as 'engine oil' in color and texture [2]; spillage of the cyst contents into spaces containing cerebrospinal fluid (CSF) may lead to chemical meningitis and possibly secondary hydrocephalus [32]. Some authors advocate inserting a catheter with an Ommaya reservoir to allow for intermittent drainage, combined with radiation therapy [51]; long-term catheter placement, however, is associated with risks of infection, catheter displacement, content re-accumulation due to cyst septations, and pain with Ommaya reservoir tapping. Remarkably, none of the NTVA studies summarized in Table 1 reported the occurrence of chemical meningitis or delayed hydrocephalus secondary to the communication of CSF spaces with the cyst.  The low complication and recurrence rates ( Table 1 and Table 3) following NTVA, as well as the endoscopic endonasal approach, compared to microsurgery and Ommaya reservoir insertion, support the validity of these minimally invasive techniques as credible and potentially better alternatives in the management of CC or cystic-dominant craniopharyngiomas. This conclusion is limited by the small number of reported NTVA cases and the heterogeneity of the published studies.

Conclusions
The NTVA is efficient, reliable, and safe for managing CC and cystic-dominant craniopharyngiomas, with potentially lower recurrence and complication rates compared to microsurgery and Ommaya reservoir insertion. Future randomized clinical studies comparing the various treatment modalities of CC are needed to solidify these conclusions.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.