Cranial Nerve Preservation following Surgical Treatment for Epidermoid Cysts of the Posterior and Middle Fossae

Introduction: Epidermoid cysts are rare lesions, accounting for 0.2 to 1.8% of all intracranial tumors. Their most common location is the cerebellopontine angle (CPA) where they may cause neurologic complications due to mass effect on the nearby cranial nerves, vascular structures and the brainstem. Presenting symptoms frequently include hearing loss, dizziness, gait disturbance, trigeminal neuralgia, headache, tinnitus, and, if ruptured, hydrocephalus. Treatment of epidermoids is surgical, with the goal of complete resection and preservation of the surrounding cranial nerves, vasculature and brain parenchyma. This can result in total resolution of symptoms, but may not be advisable due to the cysts’ close proximity and adherence to surrounding structures. Incomplete resection tends to lead to epidermoid cyst recurrence, but due to their slow and linear-growing nature, it may take several years before the patient becomes symptomatic again. There are reports in the literature where more aggressive approaches resulted in complications including permanent nerve damage. We believe that preservation of the cranial nerves should be a primary goal, determining the extent of resection. With consistent long-term follow up, epidermoid cysts can be successfully and safely managed with subsequent surgeries if necessary.

Methods: We conducted a retrospective review from 1998 to 2016 and compiled a series of 26 posterior and temporal fossae epidermoid cysts operated on at our institution. Cases were evaluated for presenting symptoms, history of prior resection, extent of resection, postoperative symptoms or deficits, complications and need for re-resection.

Results: We report 26 cases of epidermoid cysts in total. 21 were in the posterior fossa, including 11 in the CPA. The remaining 5 were middle fossa lesions. Patients presented with a variety of symptoms, including headache, dizziness, gait instability and, in 9 of 28 patients, cranial nerve deficits. Of the patients who presented with cranial nerve (CN III- XII) deficits, 2 patients had improved symptoms post-operatively, while the other 7 maintained stable cranial nerve function. The decision to perform surgery was based on age, tumor growth, severity of symptoms, and location of the lesion among other factors. Complete or near-complete resection was achieved in 17 (64%) of our patients. Of the remaining 9 with residual lesion, 7 had to undergo reoperation at an average of 3 years post the original surgery. The other two were watched closely with follow-up MRI. However, whether complete or incomplete resection, all patients in this series have stable or improved cranial nerve function as of our latest follow-ups.

Conclusion: Complete resection of posterior fossa epidermoid cysts is the primary goal of therapy, but, in our opinion, preservation of cranial nerves should remain a high priority. Utilization of careful surgical technique and intraoperative monitoring may maximize extent of resection and cranial nerve function preservation. However, in patients who have undergone incomplete resections, serial magnetic resonance imaging (MRI) and subsequent surgeries may be required.