Role of MRI as first-line modality in the detection of previously undiagnosed otosclerosis: a single tertiary institute experience

Abstract

Background: Otosclerosis causes conductive, sensorineural and mixed hearing loss (CHL, SNHL, MHL) and tinnitus in young adults. It is best diagnosed on high-resolution CT (HRCT). Occasionally, patients presenting with SNHL and/or tinnitus may undergo temporal bone MRI as the first investigation. In this study, we have described the role of MRI as the first-line modality in the detection of previously undiagnosed otosclerosis. Using search words 'MRI otosclerosis' we found 15 cases in the PACS of our institute, (University Hospitals, KU Leuven, Belgium) from 2003 to 2018. Of these, 2 were known cases of otosclerosis, hence excluded from the study. The remaining 13 patients underwent MRI as first-line investigation for unilateral SNHL (8/13), bilateral SNHL (3/13), unilateral MHL (1/13) and bilateral pulsatile tinnitus (1/13). All MRI studies were reported by the same senior radiologist. Results: Of these 13 cases, 12 were reported as showing MRI features suspicious for otosclerosis. The typical positive findings in these cases were intermediate T1 signal and post-contrast enhancement in the perilabyrinthine/ pericochlear regions. Out of 13 patients, 9 underwent subsequent HRCT, confirming otosclerosis in all. The single MRI which was reported as normal initially showed otosclerosis on HRCT. Retrospective evaluation of this MRI study showed subtle positive findings of otosclerosis. Conclusion: The end point of this study was to validate the subtle findings of otosclerosis on MRI, by comparison to the gold-standard modality HRCT. Our hypothesis is that in the appropriate clinical setting, familiarity with MRI features of otosclerosis would increase the diagnostic 'catch' in the first 'net' itself i.e. first-line MRI.

Role of Radiologic Imaging in Otosclerosis

“…MRI findings of otosclerosis are subtle and easily overlooked. Classic antefenestral involvement is less commonly identified on MRI, whereas retrofenestral involvement is more conspicuous and is characterized by intermediate T1 signal and mildmoderate enhancement [9,25,26]. Occasionally, curvilinear increased T2 signal in the peri-cochlear region can also be seen [26].…”

“…Classic antefenestral involvement is less commonly identified on MRI, whereas retrofenestral involvement is more conspicuous and is characterized by intermediate T1 signal and mildmoderate enhancement [9,25,26]. Occasionally, curvilinear increased T2 signal in the peri-cochlear region can also be seen [26]. This is not a finding exclusive to otosclerosis, as retrofenestral enhancement is also present in the acute/ subacute phase of labyrinthitis ossificans [27].…”