Cerebellar Compression by Giant Extracanalicular Osteoma with Central Cholesterol Granuloma

Abstract

Temporal bone osteomas comprise 0.1-1% of benign tumors involving the skull, the majority of which arise in the external auditory canal. More rarely, they can arise from the mastoid portion of the temporal bone. These generally present as a slow growing skull base lesion that can cause cosmetic deformity, headache, and/or hearing loss. Here, we report a case of extracanalicular mastoid osteoma uniquely presenting with posterior fossa and cerebellar compression with associated dizziness and imbalance.

Figure 1

Initial computed tomography scan showing right bony thickening, sclerosis, and expansion centered around right posterior petrous temporal bone with extension into the posterior external auditory canal with central lucent structure. There is compression of the right posterior fossa.

Figure 2

Magnetic resonance imaging in T1 (a), T2 (b), and T2 flair (c) sequencing showing bony expansion and sclerosis of the right temporal bone, fluid within this expansion, and mass effect involving the posterior fossa.

Figure 3

Preoperative audiometric evaluation (a) showing right moderate conductive hearing loss. Postoperative audiometric evaluation (b) showing normal right hearing thresholds.