Trigeminal Neuralgia Secondary to Epidermoid Cyst of the Anterolateral Cisterns of the Brainstem

Objective: Epidermoid cyst (EC) is a slow growth tumor of embryonic origin resulting from ectodermal inclusion during neural tube closure. EC is manifested in advanced stages of life, and can be incidentally diagnosed during imaging studies or when they stimulate any of the adjacent nerves as part of the hyperactive dysfunction syndrome (HDS) of the cranial nerves. ECs represents the third most frequent cerebellopontine angle (CPA) tumors, which in turn represent 1% of all intracranial tumors. Due to its noninfiltrative nature, extra-axial location and irregular extension through the anatomical corridor of the brain cisterns with displacement of the brain-stem, we proposed to call it epidermoid cyst the anterolateral cisterns of the brainstem (ACB). Methods: During January 2014 to August 2021, a total of 2,280 patients with clinical and imaging diagnosis of TN were treated at our institution and EC tumors from the ACB were found in 33 patients. We performed a tumor removal with our minimally invasive microsurgical technique with a retrosigmoid infra-asterional approach under microscopic vision assisted by endoscopy. Follow-up was performed from up to 90 months. Results: The EC was found in 1.4% of the patients who presented TN in our unit. The average age was 42 years old (21–82) with a female:male ratio of 4:3. All patients underwent a simple 3D volumetric magnetic resonance sequence showing the presence of an extra-axial lesion in the ACB compatible with EC. We operated 26 patients, 2 were not intervened due to a previous treatment with gamma-knife radiotherapy without any improvement and 5 were treated in another institute. In the operated group, 22 (85%) of patients had total tumor removal including pseudocapsule, in the remaining 4 (15%) it was decided not to remove the tumoral implant adhered to neurovascular structures due to high risk of causing a permanent neurological damage or disabling clinical condition. During the follow-up, the imaging studies showed 1 patient with an implant size <0.5 cm 3 (3.8%), 2 patients with <1 cm 3 (7.7%), and 1 with implant >2 cm 3 (3.8%). At the end of the study, all patients remained asymptomatic and without any related surgical intervention after 1 to 7 years of follow-up. Conclusion: As one of the largest series of EC of ACB published in Latin America and with excellent long-term clinical results obtained, we propose the retrosigmoid infra-asterional surgical approach as the best alternative of treatment for EC. We recommend not removing the implant site when it is strongly attached to the brainstem due to high risk of irreversible, disabling, or fatal neurological injury ([ Fig. 1 ]). Fig. 1 MRI of a patient with total resection of the epidermoid cyst. ( A ) Preoperative image. The red arrow indicates extra-axial neoplasm in the right cisternal space with trigeminal nerve displacement. ( B ) Postoperative image. The red arrow indicates the free cisternal space with repositioning of trigeminal nerve. Publication History Article published online: 15 February 2022 © 2022. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany