Endoscope-Assisted Transmastoid Infralabyrinthine Drainage of Petrous Apex Cholesterol Granuloma

We report a case of a transmastoid endoscopic-assisted decompression of cholesterol granuloma within the petrous apex in an 18-year-old woman. This patient was referred as an outpatient to our neuro-otology practice. The patient had presented with long-standing history of left-sided pulsatile tinnitus, aural fullness, and headaches. Following thorough clinical evaluation, imaging revealed a large left-sided petrous apex cholesterol granuloma. A transmastoid infralabyrinthine approach was chosen due to the anterior and inferior location lesion, in addition to preserving the cochlear and vestibular organs. Intraoperatively, access was limited due to the sigmoid sinus posteriorly and jugular bulb inferiorly. An angled 30-degree otologic endoscope was introduced, and the cholesterol granuloma cyst was identified. A 21-gauge Angiocath was adapted and employed to enter the diseased air cells. Suction was applied to the Angiocath, and fluid was drained from the involved cells. A stent was then placed endoscopically. Postoperatively, the patient showed signs of clinical improvement with resolution of the aural fullness, tinnitus, and headaches.

Cholesterol granulomas are the most common cystic lesions noted in the petrous apex. Although the genesis is controversial, they are thought to arise from a foreign body giant cell reaction to cholesterol deposits of trapped blood products within post-traumatic or obstructed mastoid air cells. Patients typically present with a myriad of symptoms including: hearing loss, retrobulbar headaches, tinnitus, dizziness, and facial twitching. The differential diagnosis includes cholesteatoma, fluid, mucocele, and neoplasia. MR imaging is helpful showing the pathognomonic hyperintensity on T1 and T2 images, whereas computed tomography does not enhance with contrast and is typically used to follow the progression of disease. The crux of treatment lies in the ability to create an open aerated cavity.

Traditional surgical approaches to the petrous apex are varied with selection typically dependent on the presence of serviceable hearing and the location and extent of disease. These approaches include: infracochlear, infralabyrinthine, middle fossa, transsphenoidal, transtemporal, translabyrinthine, and transcochlear. We feel that the use of the endoscopic-assisted approach allows for adequate surgical drainage and aeration of diseased cells while minimizing surgical risk around critical neurovascular structures.