Epidermoid cyst of the anterior clinoid process: report of a unique finding and literature review of the middle cranial fossa locations.

Background: Epidermoids cysts are relatively rare, benign, congenital tumours, representing from 0.3% to 1.8% of all intracranial lesions. When extradural, they are most commonly reported in the temporal or parietal bones as intradiploic lesions; when intradural their most common location is the cerebellopontine angle and less frequently the middle cranial fossa. Herein we present a unique case of an extradural-intraosseous epidermoid cyst of the anterior clinoid process, integrating our single-case experience into a focused literature review of these lesions, when located in the middle cranial fossa.

Case Description: A 49 years old man came to our attention with history of head trauma. Urgent brain CT and elective brain MRI showed imaging suggestive for an anterior clinoid process epidermoid cyst. Through a pterional approach, the lesion was completely removed with microsurgical endoscope assisted technique. MRI at one year follow up showed no recurrence.

Methods: Current literature on epidermoid cysts located in middle cranial fossa was reviewed. A total of 22 papers, containing 70 epidermoid cyst were selected for the review. Symptoms at presentation; anatomic location; surgical approach; extent of resection and recurrence; outcome after surgery and at follow up were analysed for each case.

Conclusions: In the 70 published cases of middle fossa epidermoid cysts, the majority presented with trigeminal neuralgia. Most of the cases were operated through a pterional approach, while recent literature showed an increasing interest in endonasal endoscopic techniques. Subtotal resection is not a straight predictive value for recurrence; post-operative neurological deficits incidence is low and generally resolve at follow-up.