• Ashutosh Kumar, Jayesh Sardhara, Pawan Kumar Verma, Kamlesh Singh Bhaisora, Arun Kumar Srivastav, Awadhesh Jaiswal, Sanjay Behari, and Raj Kumar.
• Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India.
• Neurosurgery. 2023 Jul 1; 93 (1): 112119112-119.

BackgroundPosterior fossa midline epidermoid tumors (PFMETs) include the epidermoid tumors of the cisterna magna (CM) and fourth ventricle (FV).ObjectiveTo report tumor epicenter-based classification of PFMETs and its clinical and surgical implications with outcome.MethodsOn retrospective analysis of operated cases of intracranial epidermoid tumors, 19 (N = 19) patients having tumor epicenter within FV, CM, or both were included. Cerebellopontine and prepontine cistern epidermoid were excluded. Tumor location was decided based on preoperative MRI and intraoperative findings. Major complication was defined as new onset or worsening of cranial nerve (CN) deficit, sensory motor impairment, or tracheostomy.ResultsThe mean (±SD) age of the patients was 42.0 ± 11.6 years (range 25-61 years), with no sex predilection (male:female: 1:0.9). The most common symptoms were cerebellar dysfunction, headache, vomiting, and diplopia. Common CNs affected were VII, V, lower cranial nerve, and VI. The PFMETs were classified based on tumor epicenter as type 1 (tumor epicenter in CM, n = 4/21.1%), type 2 (FV, n = 5/26.3%), and type 3 (involved CM and FV, n = 10/52.6%). Type 2 tumors had a higher incidence of raised intracranial pressure and only facial nerve palsy as preoperative CN deficit. Type 1 tumors had the least incidence of postoperative major complications. Type 3 tumors were the largest and had a greater incidence of brainstem adhesion and postoperative complications. The tumor size, duration of symptoms, and patient age were higher in patients with brainstem adhesion (5.3 ± 1.0 cm, 21 ± 16 months, 44.1 ± 9.2 years) as against its absence (4.8 ± 1.3 cm, 11.2 ± 7.3 months, 38.2 ± 11.7 years). Inferior medullary velum and tela choroidea have a critical role in tumorogenesis, tumor extension, and brainstem adhesion.ConclusionPFMETs can be classified into 3 subtypes based on tumor epicenter having clinical and surgical implications. Less aggressive dissection and near total excision in the presence of brainstem adhesion yield favorable outcomes.Copyright © Congress of Neurological Surgeons 2023. All rights reserved.

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