Petrous apex cholesterol granuloma: maintenance of drainage pathway, the histopathology of surgical management and histopathologic evidence for the exposed marrow theory

Abstract

Objectives: (1) To assess the maintenance of drainage pathway patency in patients who undergo surgical management of cholesterol granulomas, (2) to review the histopathologic and radiologic changes associated with surgical drainage of petrous apex (PA) cholesterol granulomas, and (3) to provide histopathologic evidence regarding the exposed marrow theory of PA cholesterol granulomas.

Study design: Retrospective case review and histopathologic analysis.

Setting: Tertiary referral center.

Patients: Records of 17 patients with surgically managed PA cholesterol granulomas were reviewed. Histopathologic analysis was performed on temporal bones of 11 patients with PA cholesterol granulomas from the Temporal Bone repository at the House Research Institute.

Interventions: Surgical drainage of PA cholesterol granulomas; follow-up radiologic imaging (computed tomography or magnetic resonance imaging), when available.

Main outcome measures: Primary outcome is demonstrated maintenance of a PA outflow drainage pathway after the surgical drainage procedure as assessed by radiologic imaging, available histopathology, and/or recurrence of symptoms indicating failure of maintenance. Other measures include need for revision surgery and histopathology findings.

Results: A majority (65%) of patients exhibited maintenance of their PA drainage pathway. Histopathologic evidence suggests that the PA drainage pathway can be maintained for many years after surgical drainage. Recurrence of symptoms was related to obstruction of the drainage pathway by fibrous tissue and/or granulomatous tissue. Placement of a stent improved the patient's chance of remaining symptom-free, with recurrence of symptoms and revision surgery required in only 2 stent cases (18%) as compared with 83% of those with no stent (p ≤ 0.035). Histopathologic evidence for the exposed marrow theory of PA cholesterol granulomas was found.

Conclusion: The majority of patients who undergo surgical drainage of PA cholesterol granulomas remain symptom-free after surgical drainage. Histopathologic analysis of temporal bone specimens provides evidence supporting the exposed marrow theory of PA cholesterol granuloma formation. Loss of patency of the PA drainage pathway may be an important predictor for symptomatic recurrence of PA cholesterol granulomas. Placement of a stent may decrease the likelihood of symptomatic recurrence.

Fig. 1

Axial CT image demonstrating maintenance of the petrous apex (PA) outflow tract with stent in place.

Fig. 2

Partially sectioned embedded temporal bone from patient with a cholesterol granuloma (cyst and fat) drained into the mastoid by an angiocath (ac). Temporal mandibular joint (tmj), Eustachian tube (et), external auditory canal (eac), tympanic membrane (mt), middle ear (me) carotid artery, one segment containing clotted blood (ca). (Hematoxylin and Eosin [H&E] X 5)

Fig. 3

Section made close to the level of Fig. 1. remnants of cyst (c), angiocath path (ac), fat replacing cyst (f), hematopoietic bone marrow (m), temporal mandibular joint (tmj), eustachian tube (et), external auditory canal (eac), tympanic membrane, displaced (mt), middle ear (me) cochlea (coch), posterior semicircular canal (pc), endolymphatic duct (ed). (Hematoxylin and Eosin [H&E] X 5).

Fig. 4

Cyst (c) and angiocath (ac). Carotic artery (ca), connective tissue surrounding cyst (ct), Newly formed fat (f), cochlear (coch). (H&E X 10)

Fig. 5

New bone (arrows) surrounding angiocath. (H&E X 20)

Fig. 6

Hematopoietic marrow adjacent of fat in remnant of cyst. (H&E X 100)

Fig. 7

Cholesterol granuloma in former air cell. Clefts left from dissolved cholesterol crystals are present in the remaining fluid as well as the surrounding proliferating granulation tissue containing foreign body giant cells (arrow). (H&E X 100)

Fig. 8

Hematopoietic marrow (m) adjacent of an apical air cell (aac) in an unrelated case (H&E X 100)

Fig. 9

Marrow mucosa connections in infant. (H&E X 100)