Epineurial pseudocyst of the facial nerve: prevalence and clinics

Objective: Epineurial pseudocysts (EPs) of the facial nerve are considered uncommon, benign lesions originating from and in close correlation with the mastoidal segment of the facial nerve. The objective of this study was (i) to investigate the prevalence of EP in a large study population undergoing a cone-beam computed tomography (CBCT) of the temporal bone for various neurotological reasons, (ii) to discuss the imaging features of EP, and (iii) to evaluate a potential correlation between the EP of the facial nerve and clinical neurotological symptoms. Methods: A retrospective review of 559 CBCTs of the temporal bone was performed to investigate the occurrence of EP. Radiological characteristics, demographic information, relevant medical history, neurotological symptoms, and findings from the EP positive cases were analyzed. Results: The prevalence of EP was 1.61%. Characteristic radiological features of EP included a sharply delineated, round to oval structure with soft tissue density in proximity and posterior to the mastoidal segment of the facial nerve. Although in close relation to the facial nerve, no association with facial motor signs was observed. Conclusion: EP cannot be regarded as an infrequent lesion. EP is an incidental finding in which clinical findings and complaints appear to be unrelated to the presence of EP.