Endoscopic Endonasal Removal of Orbital Schwannoma

Key Message: Resection of medially located orbital schwannomas using an endoscopic endonasal approach is a safe and effective minimally invasive option. Orbital schwannomas are benign, encapsulated, and slow-growing tumors that comprise 1% of all orbital lesions. They commonly arise from the sensory nerves within the superior orbit, most commonly from the supraorbital and supratrochlear nerves.[1,2] Here, we demonstrate endoscopic endonasal excision of a medially located intraconal schwannoma. Objective We have demonstrated that medially placed intraconal lesions can be safely excised through the endonasal corridor. Procedure The operation takes place with the patient supine. The head of the bed is elevated, and the patient’s neck is slightly extended and rotated toward the nostril to be used for the procedure. The video monitor is positioned behind the patient’s shoulder, directly along the surgeon’s line of vision. The procedure starts with the middle turbinectomy and gaining binostril access. That is followed by anterior and posterior ethmoidectomy with skeletonization of the lamina papyracea. Lamina papyracea is opened, and subsequently, the tumor is dissected all around, trying to preserve the neurovascular bundle around it. Reconstruction is followed after achieving hemostasis. Video timeline with audio transcript 0.01–0.06 minutes: In this neurosurgical video, we demonstrate endoscopy endonasal excision of orbital schwannoma. 0.07–0.10 minutes: A 22-year-old man came with progressive painless proptosis without any diplopia. 0.11–0.17 minutes: In this clinical image, we can see the patient has an axial proptosis with slight deviation laterally and inferiorly. 0.18–0.31 minutes: MRI imaging showed medially located intraconal lesion, displacing the ocular bulb, laterally and inferiorly. The optic nerve is displaced laterally. The lesion appears to be closer to the medial wall of the orbit and approachable through trans nasal route. 0.32–0.42 minutes: In our practice, we have been approaching medially located lesions through endoscopic, trans nasal route, laterally located tumors through lateral orbitotomy and superiorly located tumors through a transcranial approach. 0.45–1.10 minutes: Initially, to gain a wide access, we did the right side middle turbinectomy. Then, on the left side, we did elevation of a small mucosal flap, dissected the cartilage and removed part of it to access the operative site through the left and have a binostril access. 1.11–1.18 minutes: So, this is how we elevated it, used the navigation to identify the anatomical landmarks. 1.20–1.27 minutes: Then, we used soft tissue debrider to remove mucosa and open posterior ethmoidal air cells and expose the lamina Papyracea. 1.29–1.36 minutes: Under navigation guidance, the lamina papyracea is opened and dissected carefully from the periorbita. 1.37–1.59 minutes: The periorbital is opened anteroposteriorly, and in the anterior part, it is opened superior-inferiorly. We can see the fat protruding out through the opening. A blunt dissector is used to dissect all around to dissect the muscles as well as the tumor located within the periorbita. 2.00–2.40 minutes: After dissecting and identifying the medial rectus muscle, it was decided that the lesion has to be approached through a window between the medial rectus and the superior rectus. A blunt ball probe was used to dissect the tumor all around. It was very important to set the tumor free from the periorbital fat as much as possible. Then, we decided that the whole tumor cannot be removed through dissection all around, so a small opening was done. A ring curette was used to decompress the lesion as much as possible. After that, we decided that a soft tissue debrider can be used to decompress some part of the tumor. 2.41–3.02 minutes: We had to adopt the same principles of resecting any other intracranial schwannoma. Internal decompression as much as possible, and after that, dissecting the capsule around. Some amount of controlled traction had to be put to dissect the tumor wherever the tumor has been decompressed a bit. 3.04–3.30 minutes: Part of the tumor has been delivered into the nasal cavity with a residual attachment still in the orbit. To remove that part inside the nasal cavity a soft tissue debrider was used. Since it was a large tumor, decompression of lesion in staged manner, followed by dissection of the intraorbital cavity had to be done. 3.31–4.02 minutes: During this step, care had to be taken so that debrider only is in contact with the tumor for decompression and not in contact with the muscles. Blunt dissection of the tumor had to be done to remove the tumor left behind inside the cone. This dissection had to be done between the superior rectus and the medial rectus. A window was created by placing a cotton ball between two muscles to inspect the intraconal contents. 4.03–4.35 minutes: After it was confirmed that the lesion has been totally excised, hemostasis was done using the hemostats. Bone reconstruction of the medial wall of the orbit was not done after hemostasis. The mucosal flap which was taken on the left side was replaced and sutured. The middle turbinate, which was lateralized, was medialized to its original place. Nasal packing tamponade is applied. 4.36–4.45 minutes: After surgery, the patient’s proptosis resolved and had conjunctival chemosis and medial rectus paresis was present, which improved over time. 4.46–4.55 minutes: Postoperative MRI showed complete excision without any residual lesion. At 6 months, the patient was doing well with mild medial rectus paresis. 4.56–5.06 minutes: Although many strategies have been used to approach orbital tumors, patients should get optimal surgery tailored to the pathology, anatomic relationship to the optic nerve and surgeon comfort. Video link https://youtu.be/hqNlga2fkns QR Code: Video timeline with audio transcript. Outcome: Immediately after surgery, proptosis had resolved, and visual acuity was unaffected. He had conjunctival chemosis and medial rectus paresis, which had improved over time. At 6 months of follow-up, the patient had mild medial rectus paresis. Pearls and Pitfalls: While treating these lesions, the surgeon should be well aware of the relation of the optic nerve with the tumor. Extreme caution should be exercised while applying traction to deliver these tumors as the integrity of the optic nerve or the neurovascular bundle can get compromised. The medial rectus muscle and the orbital fat should be preserved to avoid post-operative paresis and have good cosmetic outcomes. Discussion Orbital Schwannomas are benign and slow-growing lesions that comprise 1% of all orbital tumors.[1,2] They present with progressive proptosis, diplopia, and orbital pain. The treatment strategy for these tumors takes into account the extension of the tumor and the relation of the tumor with the optic nerve and, thus, its accessibility and cosmesis as well. The neurovascular structures around the tumor should also be taken into consideration. They have been anatomically divided into intraconal, extraconal, and intracanalicular portions depending on their relationship to the muscle cone.[3] Later, approaches to these tumors were defined by their relation to the optic nerve by Paluzzi et al.,[4] and a clock model was proposed. They proposed the extra orbital approaches viz the classic FTOZ approach or the transorbital approaches viz anterior orbitotomy, lateral orbitotomy, medial orbitotomy, or a combination of these approaches. An endoscopic endonasal approach was also described for the tumors in the medial and inferior positions of the clock model. The endoscopic approach is a safe option.[5] However, the risk of manipulation of the neurovascular bundle and resulting postoperative transient paresis persists.[6] The drawback of this approach is a steep learning curve and the difficulty to maneuver the endoscope with ease in a narrow corridor, along with an increased risk of injury to the surrounding neurovascular bundle.[7] Conclusion The endoscopic endonasal approach is an extremely feasible, safe, and effective option in the armamentarium of neurosurgeons for treating medially placed, intraconal orbital lesions. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.