Surgical Approach Selection for Posterior Fossa Epidermoid Cysts: The Combined Posterior Petrosal Approach does not Incur Increased Perioperative Morbidity as Compared to the Retrosigmoid Approach

Introduction: Epidermoid cysts of the skull base are congenital lesions within subarachnoid cisterns that slowly expand over decades. Lesions are found incidentally or present with cranial neuropathies and/or brainstem compression. Treatment for symptomatic lesions is complete removal of cyst contents and capsule, while avoiding injury to the cranial nerves and brainstem. The recurrence rate is 10–30% at 10 years, due to microscopic residual cells or missed gross contents during surgery. The retrosigmoid approach is most often used, however, despite improved endoscopic supplementation, its visualization and surgical reach is limited. The posterior petrosal presigmoid approach offers increased visualization and reach, however, many believe it carries a higher morbidity. We aim to compare the differences between retrosigmoid and posterior petrosal presigmoid approaches based on epidermoid cyst location, size, anatomic characteristics, and complication rate. Methods: A retrospective, single-institution cohort study of patients with pathologically confirmed posterior fossa epidermoid cysts undergoing retrosigmoid or posterior petrosal approaches between 1995–2025 was performed. Patient demographics, preoperative MRI findings, surgical and perioperative outcomes and follow-up data were collected from the electronic health records. Tumor characteristics, approach selection, extent of resection (EOR), post-operative outcomes, and recurrence rates were compared. Statistical analysis was performed using Wilcoxon Rank Sum, Fisher Exact tests, and Firth Logistic Regression to compare patient outcomes between surgical approaches. Results: A total of 23 patients treated through an intracranial approach for epidermoid cysts were included for the study, of which 16 underwent posterior petrosal presigmoid approach and 7 retrosigmoid. Patients average age was 42 years old and 65.2% were female. The average anteroposterior dimension was 4.3 cm. Gross total resection (GTR) was achieved in 65.2% overall, with 68.8% of the posterior petrosal group and 57.1% of the retrosigmoid group. Intraoperative cerebrospinal fluid (CSF) diversion was used in 56.3% for posterior petrosal and 28.6% for retrosigmoid craniotomies. Post-operatively, 31.3% and 14.3% required a shunt in the posterior petrosal and rectosigmoid groups, respectively. The total length of hospitalization between both groups was similar, with petrosals having an average 5.7 ± 5.0 days and patients recovering from a retrosigmoid at 4.4 ± 3.3 days. There were two recurrences overall, one in each group. There were no mortalities. Conclusion: Approach selection for posterior fossa epidermoid cysts is complex with the end goal of maximal safe lesional resection and minimal morbidity. There was no significant difference in GTR, intraoperative or postoperative CSF diversion, or length of hospital stay between the two groups. Predictive factors of achieving gross total resection between both surgical approaches were not identified by the data. If needed, a posterior petrosal presigmoid approach can be chosen without additional morbidity. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany