By Michael Castillo, MD, Resident
   Ravi N. Samy, MD
   Brandon Isaacson, MD
   Peter Roland, MD

Cholesterol granulomas (CGs) are expansile cysts that contain cholesterol crystals and are surrounded by foreign body giant cells and chronic inflammation encapsulated by thick fibrous tissue. CGs are found in many places including the peritoneum, mediastinum, thyroid, orbit, and paranasal sinuses. They were first described in the petrous apex in the mid-1980s.
The petrous apex is surrounded by the clivus medially, inner ear laterraly, carotid anteriorly and cranial fossa dura posteriorly. When seen on CT, a petrous apex CG appears as a well-defined, sharply marginated, bony expansive lesion with remodeling and erosion of bone. On MRI, there is high signal on T1 and T2 and no enhancement occurs with contrast.
Most authors describe the goal of surgical treatment of these lesions as surgical drainage and establishment of permanent aeration. One of the main questions posed by this review is: does aeration need to be established? Our goal is to review the experience at UT-Southwestern from 1980 to present. In particular we would like to examine the significance of the size of the lesion and the presence of aerated cyst cavities among post-operative patients. Do patients with unchanged cyst sizes or unaerated cavities have a higher rate of revision surgery? This study is designed as a retrospective review covering 1980 to the present. We will examine charts and radiographic images of patients with diagnosis code for cholesterol granuloma. The main outcome measures include: symptom resolution, clinical findings, imaging study results and incidence of revision surgery.
A search of patients with the diagnosis code for cholesterol granuloma identified 104 patients. Those with CG of middle ear/mastoid, cholesteatoma or other processes were excluded. At this point we have reviewed charts of 18 patients with cholesterol granulomas of the temporal bone. In this study, 11 (61%) underwent surgical management. Preoperative symptoms included: headache (4), facial nerve weakness/irritation (4), hearing loss (4), vision changes (2), tinnitus (1), vertigo (1) and facial numbness (1). Surgical approaches included: middle cranial fossa +/- mastoidectomy (5), transcochlear (2), infralabyrinthine (1), transphenoidal (1), transmastoid (1) and infracochlear (1). Postoperative symptoms resolved completely in 4 (36%) of patients. In 3 patients persistent headaches were noted. In 2 patients there was return of facial nerve irritation. Two patients have been lost to follow up. Postoperative imaging demonstrated lesions without aeration and either remained stable or increased in size in 8 patients (73%). Revision surgery was performed in 3 patients (27%) due to either facial nerve symptoms or persistent headaches.
In conclusion, the amount of petrous apex cholesterol granuloma aeration on postoperative imaging has limited correlation to resolution of symptoms or cyst enlargement. As with primary surgery, revision surgery should not depend on imaging alone but primarily on patient symptoms.