A 54-year-old female patient presented to her physician with a 3-year-old history of bilateral tinnitus and hearing loss. She also complained of paresthesia in the periauricular area. There were no episodes of imbalance or vertigo

F Govaere

I Crevits

L Dewachter

R De Man

Journal of the Belgian Society of Radiology

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Bilateral exostoses of the internal auditory canalL. Dewachter1, F. Govaere1, I. Crevits1, R. De Man1A 54-year-old female patient presented to her physician with a 3-year-old history of bilateral tinnitus and hearing loss. She also complained of paresthesiain the periauricular area. There were no episodes of imbalance or vertigo.Otologic history revealed that she had experienced a left serous otitis mediain 2008 and multiple episodes of otitis media as a child. The head and neck exam-ination yielded normal findings. Otologic examination revealed an atelectatictympanic membrane on the left side. Pure tone audiometry displayed a mildmixed hearing loss on both sides.CT and MRI scan were performed. Temporal bone CT scan (Fig. A) showedbilateral prominent broad based bony growths of the anterior openings of theinternal auditory canal (IAC) resulting in a stenosis of the IAC on the right side(Fig. A1) and a narrowing of the IAC on the left side (Fig. A2).T1-weighted MRI (Fig. B) showed a hypo-intens lesion in the anterior openingof the right IAC in contact with the statoacoustic nerve. A similar smaller lesionwas seen on the left side.The lesions showed a very low signal intensity on the 3D T2-weighted DRIVEsequence (Fig. C) which could be compatibel with bone or calcification. This wasconfirmed on the MDCT.Based on these imaging findings, the diagnosis of bilateral IAC exostoses wasmade.Because of the mild hearing loss the patient was treated conservatively andclinical follow-up was recommended.CommentExostoses, as well as osteomas are benign slow-growing bony lesions of theauditory canal. They are common in the external auditory canal but are rare inthe internal auditory canal. The cause remains unclear. Reported etiological factors are trauma, infection,inflammation, developmental and genetic abnormalities.In most cases exostoses and osteomas remain asymptomatic but they maycause symptoms due to a local compressive effect. Depending on their exactlocation and size they can manifest as hearing loss, vertigo or tinnitus.Since a biopsy specimen of the IAC cannot easily be obtained, the radiograph-ic appearance is important in differentiating between different bony lesions.Exostoses are smooth-bordered, broad-based bony lesions growing into theIAC. They are often multiple and bilateral whereas osteomas are solitary, stalkedlesions. Osteomas may also be differentiated from exostoses by the radiograph-ic appearance of bone marrow.On histologic specimen on osteoma displays fibrovascular channels withinthe bone.Exostoses and osteomas are slow growing lesions and can remain stable formany years. Treatment depends on the severity of the symptoms. Regular clini-cal follow-up and regular CT monitoring is recommended for asymptomaticlesions whereas surgical excision and decompression is the treatment of choicein patients with severe progressive symptoms.Reference1. Nguyen L., Baik F., Doherty J., Harris J., Nguyen Q.: Exostoses and Osteomas of theInternal Auditory Canal. Laryngoscope, 2010, 120: S215.JBR–BTR, 2013, 96: 91.IMAGES IN CLINICAL RADIOLOGY1. Department of Radiology, Heilig-Hart ziekenhuis, Roeselare, Belgium.A1A2BCimage-dewachter-_Opmaak 1  25/04/13  11:34  Pagina 1

Bilateral exostoses of the internal auditory canal

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Bilateral exostoses of the internal auditory canal

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