Endoscopic Endonasal Inter-dural Posterior Clinoidectomy and Pituitary Hemitranspostion for Surgical Resection of a Large Suprasellar Ependymoma Involving the Inter-peduncular Cistern

Key Message: EEA with inter-dural posterior clinoidectomy is a viable and effective option for suprasellar ependymomas, offering gross total resection with reduced morbidity. Ependymomas in the inter-peduncular cistern are formidable tumors to operate on due to their anatomical location and the potential for significant morbidity associated with their resection.[1,2] While various surgical approaches have been explored, each carries inherent risks and limitations, particularly for lesions in challenging areas like the retrochiasmatic space.[3] The advent of endoscopic endonasal approaches (EEAs) represents a paradigm shift in skull base surgery, offering direct access to midline lesions with potentially reduced morbidity and enhanced visualization.[4-6] This case report highlights the effectiveness of inter-dural posterior clinoidectomy via EEA, a less invasive method, in resecting suprasellar ependymomas from the inter-peduncular cistern with minimal morbidity. Objective: We report a case of a suprasellar ependymoma in the inter-peduncular cistern resected by an EEA with inter-dural posterior clinoidectomy and discuss the procedure's operative nuances. Clinical presentation A 59-year-old male complained of blurring of vision in both eyes for 3 months. He also had lethargy and tiredness for 1 month. On examination, he had bi-temporal hemianopia, and there was evidence of hypocortisolism on endocrinological evaluation. MRI brain was suggestive of a large tumor in the retro-chiasmatic area involving the suprasellar cistern, extending into the inter-peduncular cistern and pushing the floor of the third ventricle upward. The tumor was hyperintense on T2 and only had patchy contrast enhancement [Figure 1].Figure 1: (a-c) Pre-operative MRI images: MRI images shows a large tumor in the retro-chiasmatic area involving the suprasellar cistern, extending into the interpeduncular cistern and pushing the floor of the third ventricle upward. The tumor was hyperintense on T2 and only had patchy contrast enhancementSurgical procedure Technique [Video 1]: The patient was positioned supine, and the Mayfield head clamp was fixed with the head laterally flexed 15 degrees to the left side. The right thigh was prepared for harvesting fat or fascia lata grafts. The lumbar drain was inserted pre-operatively after induction of anesthesia in anticipation of a high flow of cerebrospinal fluid leak leak. Intra-operative image guidance utilizing pre-operatively acquired CT and MRI images was used during surgery. A right-sided nasoseptal flap was elevated and stored in the choana for use during reconstruction. A bilateral posterior ethmoidectomy, posterior nasal septectomy, and a wide anterior sphenoidotomy were performed. The upper clivus was drilled, and an incision was placed at the confluence of the inferior intercavernous sinus and the cavernous sinus on the right side. Venous hemostasis was achieved by injecting injectable hemostats. Following this, the medial wall of the cavernous sinus was mobilized away from the internal carotid artery on the right side. The inferior hypophyseal artery was then coagulated to prevent direct bleeding from the internal carotid artery and to facilitate inter-dural posterior clinoidectomy. After clinoidectomy, the dura over the planum was incised, and the incision was continued around the pituitary gland inferiorly onto the dura of the upper clivus. The intra-dural pituitary transposition was performed to increase the surgical corridor available between the optic chiasm and pituitary gland for the dissection of the tumor. The tumor was soft in consistency and could be dissected using microsurgical techniques. Meticulous dissection of the tumor from the optic chiasm and careful preservation of the superior hypophyseal artery and its branches were done. The dissection was extended into the third ventricle without damaging the third ventricular walls. Gross total resection of the tumor was achieved [Figure 2]. Reconstruction was performed in a multi-layered fashion with an inlay of fat and collagen matrix, an onlay of fascia lata, and a vascularized nasoseptal flap.Figure 2: (a-c) Post-operative MRI images: MRI images shows a complete excision of tumor with postoperative changesVideo link: https://youtu.be/TmEpKVJlymA QR Code: Video timeline with audio transcript 0.0-0.16 minutes: Endoscopic Endonasal Interdural Posterior Clinoidectomy and Pituitary Hemitranspostion for Surgical Resection Of A Large Suprasellar Ependymoma Involving the Interpeduncular Cistern 0.17-0.30 minutes: A 59-year-old patient presented to us with complaints of vision loss in both eyes for 3 months, lethargy, and tiredness for 1 month and, on examination, had bitemporal hemianopia with evidence of hypocortisolism. 0.31-1:25 minutes: The MRI showed a hyper-intense lesion on T2, involving the supra- sellar cistern extending into the inter-peduncular cistern and filling the entire third ventricle. The lesion showed only patchy enhancement on contrast. The location of the lesion is predominantly retrochiasmatic and involves the supra-sellar cistern. Because of its midline location, it is ideally suited for an endonasal approach. However, this lesion offers minimal space between the optic chiasm, which is colored yellow, and the pituitary gland, which is colored green. During the endonasal approach, there might be significant manipulation of the optic chiasm, resulting in optic dysfunction. An intra-dural pituitary transposition increases the amount of space available for surgical dissection of the tumor within this corridor. It also allows the pituitary gland to be moved toward one side, preserving its venous drainage on one side. 1:26-4:01 minutes: At the beginning of the procedure, we harvest a nasoseptal flap, which is stored in the choana for use later on during the procedure. A bilateral posterior ethmoidectomy and a posterior septectomy are performed. The upper clivus is drilled, and then we mobilize the cavernous sinus. An incision is placed at the junction of the inferior intercavernous sinus and the cavernous sinus on the right side. Venous hemostasis is achieved by injecting injectable hemostats. Following this, the medial wall of the cavernous sinus is mobilized away from the internal carotid artery on the right side. We then visualize the inferior hypophyseal artery, which needs to be coagulated and divided. This is done to prevent direct bleeding from the internal carotid artery, which can be challenging to control. Following the isolation and coagulation of the inferior hypophyseal artery, we can mobilize the posterior clinoid away from the posterior part of the dura. The clinoidectomy must be done by gently manipulating the clinoid away from its dural attachments. Following removing the posterior clinoid, we go on to incise the dura all around the pituitary gland. An initial incision is placed just above the anterior inter-cavernous sinus, and the dura is opened toward the optic nerve on the right side. Following this, the diaphragm is incised, and the dural incision is taken down toward the posterior clinoid. Once the pituitary has been transposed to the left side, the tumor is slowly dissected from the under-surface of the optic chiasm. The perforating vessels that supply the optic chiasm arise from the superior hypophyseal artery and must be preserved gently using the microsurgical technique. The tumor is slowly divided away from the vascular structure that separates it from the superior hypophyseal artery on the left side. The tumor is consistently soft and amenable to dissection using the two-suction technique. We slowly dissect the tumor from the right side of the suprasellar cistern and extend the dissection into the third ventricle. At this point, one can appreciate the walls of the third ventricle. Following tumor dissection, we then go on to extend our resection onto the left side and slowly take down small attachments that separate the tumor from the walls of the third ventricle. In this manner, the entire tumor is removed from the third ventricle, and the third ventricular walls are seen undamaged following the surgical resection. 4:02-4:26 minutes: This is the view of the supra-sellar cistern, and the pituitary stalk, the left superior hypophyseal artery, and the carotid artery can all be seen. Reconstruction is then performed in a multi-layered fashion using fat and fascia, and this is tucked into place to prevent the fascial layer from being dislodged. A nasoseptal flap is then placed. 4:27-4.50 minutes This patient had improvement in vision in both eyes and had transient diabetes insipidus after surgery. The biopsy in this particular case was an ependymoma grade 2, and in conjunction with the radiation oncologist, it was decided that this patient should undergo adjuvant radiation. At the end of 9 months, this patient continues to do well. He had transient diabetes insipidus, which is no longer present at this point in time. Outcome: Post-operatively, the patient showed significant improvement in vision and experienced transient diabetes insipidus, which was treated with desmopressin. Post- operative MRI showed a complete excision of tumor with post-operative changes [Figure 2]. Histopathological examination revealed an Ependymoma grade 2 tumor, and the patient subsequently underwent adjuvant radiation. At 9 months follow-up, the patient's condition had stabilized, with no signs of diabetes insipidus. Pearls and pitfalls The endoscopic endonasal approach offers direct access to the midline skull base and inter-peduncular cistern, allowing for excellent visualization of the tumor and surrounding structures. This approach is particularly advantageous for retrochiasmatic lesions, providing a clear view of critical areas with minimal obstruction. Despite the direct access, there is a risk of damaging neurovascular structures, particularly cranial nerve II, cranial nerve III, superior hypophyseal artery, and the posterior communicating artery. So, careful manipulation of these structures is required during tumor resection. Compared to transcranial approaches, the endoscopic endonasal route minimizes manipulation of neurovascular structures while accessing tumor in the inter-peduncular cistern, reducing the risk of post-operative neurological deficits. While offering superior midline access, this approach can be restrictive for the tumour's lateral extensions, which can lead to challenges in accessing tumor parts extending significantly to either side of the midline. EEA allows for preserving the pituitary gland and its function, which becomes especially critical in managing ependymomas that do not directly involve the gland. Though EEA is associated with less morbidity and a faster recovery compared to more invasive methods, it carries a risk of cerebrospinal fluid (CSF) leakage. Meticulous multi-layered reconstruction techniques are essential to prevent this complication. Discussion The surgical management of suprasellar ependymomas presents unique challenges due to the tumor's location and its proximity to critical neurovascular structures. Understanding the complex anatomy of the suprasellar and inter-peduncular cistern is essential for successful surgical resection.[7] Suprasellar ependymomas, being less common than infratentorial ependymomas, often necessitate a nuanced approach due to the delicate area they inhabit. These tumors can seed intra-cranially, posing additional surgical challenges.[8] The primary treatment involves surgical excision, with or without radiation therapy, as chemotherapy is generally considered ineffective for this tumor type.[9,10] Complete surgical resection is crucial for a significant survival advantage.[11,12] However, the predictive values of surgery, histology, and patient- related prognostic factors for supratentorial ependymomas remain unresolved.[13] Traditionally, transcranial approaches to the inter-peduncular cistern often necessitated substantial brain retraction and manipulation of neurovascular structures, leading to increased morbidity. This was particularly true for retrochiasmatic tumors, requiring the manipulation of the optic apparatus and pituitary gland. The EEA, with posterior clinoidectomy, offers a more direct route to these tumors. Studies have shown that EEA increases the field of view, provides superior visualization of the tumor–brain interface, allows for more precise dissection, and maximizes resection extent while preserving vital structures in this area.[14,15] EEA with posterior clinoidectomy with inter-dural pituitary transposition have effectively removed prominent posterior clinoids while preserving pituitary function.[16] Pituitary transposition and unilateral coagulation of the inferior hypophyseal artery as performed in the present case have shown to not adversely affect pituitary function, thus giving patients a better post-operative quality of life.[17,18] One of the primary concerns in the surgical management of suprasellar and inter-peduncular cistern tumors is the preservation of the superior hypophyseal artery (SHA) and its branches, which supply the optic chiasm, hypothalamus, and optic tract. The modified endoscopic posterior clinoidectomy technique provides a broader operative view, allowing for radical resection of skull base tumors while preserving the SHA and its branches.[15] Despite the advantages of the EEA, the transcranial approach should be favored in suprasellar ependymomas occupying inter-peduncular cistern if the tumor extends laterally beyond the boundaries of the cranial nerves or occupies a large area within the inter-peduncular cistern.[19] The direction of tumor growth, particularly concerning the optic chiasm and infundibulum, can be critical in determining the surgical approach. EEA may require a transcranial approach for better access of these extensions.[20] Thus, the choice of surgical approach is highly individualized based on the specific characteristics of the tumor and patient. Conclusion In conclusion, the surgical management of suprasellar ependymomas requires a thorough understanding of the complex anatomy, precise surgical technique, and careful consideration for critical neurovascular structures. The EEA represents a significant advancement in the surgical treatment of these tumors, offering a balance of efficacy and safety for improved patient outcomes. Patient's consent A full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient/relative/guardian. The journal will not be responsible for any medico-legal issues arising out of issues related to patient's identity or any other issues arising from the public display of the video. Disclosure The authors hereby certify that the work shown here is genuine, original and not submitted anywhere, either in part or full. They transfer the full rights of the video to Neurology India. All the necessary permissions from the patient, hospital and institution has been taken for submitting this video to Neurology India. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.