Lateral Orbitotomy for Resection of Trigeminal Schwannoma

Objective: Trigeminal schwannomas are the second most common schwannoma after vestibular. They can be complex tumors involving multiple intra-cranial and extra-cranial compartments. Multiple surgical approaches have been described for resection of trigeminal schwannoma including open and endoscopic endonasal approaches depending on the specific location of the tumor. Lateral orbitotomy is a well described approach for lesions in the orbit and recently has gained popularity as a surgical corridor for lesions in the middle fossa. However, the literature on the utility and surgical outcomes of this approach for trigeminal schwannomas is lacking.

Methods: Patients who underwent a lateral orbitotomy for resection of trigeminal schwannoma at our institution from 2015 to 2020 were identified. Medical records were reviewed for age, gender, pre- and post-operative trigeminal dysfunction, pre- and postoperative Barrow Neurological Institute (BNI) Pain Intensity Scale, complications, recurrence, and requirement for further treatment. All patients had pre- and postoperative magnetic resonance imaging (MRI). Preoperative location was graded based on the modified Ramina classification.

Results: Four patients underwent lateral orbitotomy for trigeminal schwannoma with a median age of 38.5 (25–74) and a female predominance (75%; [Table 1]). All patients presented with facial pain, two (50%) with additional subjective facial hypoesthesia, three (75%) demonstrated objective trigeminal hypoesthesia, and one patient had additional cranial nerve palsies including a partial abducens palsy and optic neuropathy. All patients had a pre-operative BNI pain intensity score of III and above (III, IV, IV, V) with a mean duration of symptoms of 18.3 months. One patient had a purely Ramina group C tumor contained to the middle fossa, two patients had the majority of their tumors in the middle fossa with small posterior fossa dural extension, and one patient had a Ramina group E tumor with both middle fossa and posterior fossa extension ([Fig. 1]). All patients underwent a lateral orbitotomy approach in conjunction with an oculoplastic surgeon and all had gross total resection without new trigeminal dysfunction ([Fig. 2]). None of the patients experienced postoperative venous infarcts or seizures. Three of the four patients demonstrated improvement in their trigeminal hypoesthesia and BNI pain intensity score, one patient had a stable pain score postoperatively. One patient with preoperative corneal numbness had persistent postoperative V1 dysfunction and unfortunately developed neurotrophic keratopathy requiring serum treatment with improvement. None of the patients experienced recurrence of their tumor or required additional treatment (mean follow-up of 30 months).

Conclusion: This series demonstrate the safety and efficacy of lateral orbitotomy as a minimally invasive extra-dural approach for the resection of trigeminal schwannoma. It is most suitable for tumors limited to the middle fossa (Ramina group C) but is also feasible for appropriately selected tumors with either extra-cranial or posterior fossa extension. This approach allows for direct access to Meckel's cave and allows for dissection of the tumor along the long axis of the nerve fibers and tumor. This approach represents an additional tool in the armamentarium for the surgical resection of trigeminal schwannoma minimizing surgical incision, reducing brain retraction, soft tissue dissection, and bony removal.

Fig. 1 Lateral orbitotomy approach for Ramina group E trigeminal schwannoma. 70 year old female presents with three month history of double vision and right V1 numbness. Neurological exam notable for a partial right CNVI palsy and V1 numbness. MRI demonstrated and enhancing mass along right CNV with widening of the porous trigeminus consistent with a Ramina group E trigeminal schwannoma. Axial (A), Sagittal (B). The patient underwent right lateral orbitotomy for resection with an uncomplicated post-operative course. Post-operative MRi demonstrated gross total resection of the tumor (C). The patient had improved in her right CNVI palsy and persistent V1 numbness.

Fig. 2 Illustrative case of lateral orbitotomy for resection of trigeminal schwannoma. 24 year old female presents with 4 years of right V2 trigeminal neuralgia. MRI demonstrated a heterogeneously enhancing mass centered in the right Meckel's cave (A). A lateral orbitotomy provides direct corridor to this lesion (B). Intraoperative exposure after removal of the lateral orbital rim from the fronto-orbital suture down to the zygomatic process (C). This approaches allows for opening parallel to the nerve fibers into Meckel's cave with visualization of tumor (T) between the V2 and V3 fibers (D). Standard microsurgical approach is carried out with debulking and dissection of the tumor capsule to remove the tumor (E). An endoscope is used to check the underside of the nerve fibers and posteriorly to the porous trigeminus (PT) to ensure complete resection (F,G). Fat graft is used to fill the defect (H). Post-operative MRI demonstrated gross total resection of the tumor (I).

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Artikel online veröffentlicht:
15. Februar 2022