Surgical Considerations in Addressing Cholesterol Granuloma of the Petrous Apex through an Infracochlear Approach

Abstract

Cholesterol granuloma of the petrous bone is a foreign body giant cell reaction to cholesterol deposits with symptoms including hearing loss, vestibular dysfunction, and cranial nerve deficit as a result of cystic mass compression. Surgical treatment is often difficult to plan due to limited access to the lesion and possible injury to surrounding structures. We report on a case of petrous apex cholesterol granuloma drainage through an infracochlear approach. A 27-year-old female patient presented with acute diplopia due to left-sided abducens paralysis. Multislice computed tomography (MSCT) and magnetic resonance (MR) imaging described a 3.5-cm well-marginated lesion in petrous bone apex, compressing the left abducens nerve at the point of entry into the cavernous sinus, corresponding to cholesterol granuloma. The patients was surgically treated through a transcanal infracochlear approach, since preserving the external and middle ear conduction mechanisms was paramount for the patient. The patient was discharged on the second postoperative day and diplopia resolved within 5 days postoperatively. Six months after the surgery, her hearing on the left side is normal, and she remains symptom-free. This case underpins the value of preoperative planning when approaching the petrous apex, an anatomically complex area due to abundance of important neurovascular structures crowded in a narrow and confined region.

Keywords: Anatomy; Cholesterol granuloma; Infracochlear approach; Petrous apex; Temporal bone.