Osteoma of the Internal Auditory Canal Mimicking Vestibular Schwannoma: Case Report and Review of 17 Recent Cases

Abstract

Osteoma of the internal auditory canal (IAC) is an uncommon benign bone tumor. Its imaging features may be similar to other IAC lesions, such as vestibular schwannomas that are benign and usually slow-growing but sometimes life-threatening tumors. Thus, detecting IAC lesions and differentiating osteoma from other IAC lesions are both important clinically. We report a case of misdiagnosis of an IAC osteoma as an IAC schwannoma based on magnetic resonance (MR) imaging using the three-dimensional constructive interference in steady state (CISS) sequence instead of T1-weighted MR imaging with gadolinium. We also review 17 cases of IAC osteomas reported in the past 22 years. A 61-year-old female was admitted to our department with IAC lesion incidentally discovered by the CISS sequence. The lesion was diagnosed as an IAC schwannoma, and was followed up annually under "wait and scan" management. Follow-up T1-weighted MR imaging with gadolinium showed no enhancement of the tumor, and additional computed tomography (CT) of the temporal bone showed a solitary pedunculated bony lesion, resulting in the diagnosis of IAC osteoma. The CISS sequence is useful for detecting small IAC lesions, such as vestibular schwannomas. However, the CISS sequence has limitations for qualitative diagnosis and can misdiagnose osteomas as schwannomas. Use of the CISS sequence without T1-weighted MR imaging with gadolinium for the screening of a lesion of the IAC and cerebellopontine angle should consider the possibility of IAC osteomas, and temporal bone CT or T1-weighted MR imaging with gadolinium should be performed when an IAC lesion is detected.

Osteoma of the Internal Auditory Canal as a Rare Finding in Imaging: A Case Report

“…A review of the literature by Suzuki et al (2014) of 17 cases of CAI osteoma identified several clinical features, namely: a mean patient age of 44.1 years (male:44; female:44.2), a female-to-male sex ratio of 1.4:1, bilateral localization for 2 cases. Six cases were identified incidentally (12%), including our case who was asymptomatic on the affected side at detection, 7 cases had subjective or objective hearing loss (41%), 10 cases had tinnitus and/or auditory fullness on the affected side (59%), 11 cases had vertigo and/or dizziness (including medical history) (65%), and 2 cases had facial palsy [6][7][8][9][10][11][12].…”

Mastoid osteom: Olgu Sunumu

“…Osteomlar baş boyun bölgesinde frontal etmoid bölgede, maksiler sinüste, mandibulada nadiren de temporal kemikte izlenir [3,4]. Temporal kemikte olan osteomlar dış kulak yolunda, orta kulakta, akustik kanalda, petröz apekste ve nadiren mastoid kortekste izlenir [ 5,6,7]. Baş boyun bölgesinde olan benin tümörler içerisinde mastoid kemik osteom insidansı % 0.1-1 arasında bildirilmiştir [8].…”

Internal auditory canal osteoma

“…Osteomas are slow-growing benign bone tumors commonly observed in the temporal bone, especially in the mastoid cortex and external auditory canal. Its appearance in the IAC is very rare and is usually discovered incidentally [1]. The main differential diagnosis is with Exostosis.…”

“…Unlike the Osteoma, Exostosis usually present with multiple bilateral lesions with a broad implantation base [2]. CT is the most effective diagnostic tool for this type of bone lesions [1].…”