From the Guidelines
The definitive diagnostic test for otosclerosis is a high-resolution thin-section temporal bone CT (HRCT) without IV contrast, as it provides excellent accuracy in identifying changes of otospongiosis (otosclerosis) and other conditions that cause pulsatile tinnitus. While surgical exploration of the middle ear called an exploratory tympanotomy can also confirm the diagnosis, it is not typically performed solely for diagnostic purposes. Temporal bone CT scans, as mentioned in the study by 1, are considered the first-line imaging modality in patients presenting with conductive hearing loss without any mass lesion seen within the middle ear cavity. The study by 1 also supports the use of HRCT in evaluating pulsatile tinnitus, including otosclerosis.
Key Points to Consider
- Otosclerosis can appear as a pinkish retrotympanic lesion (Schwartz sign) on otoscopy, but HRCT is necessary to confirm the diagnosis.
- HRCT without IV contrast is sufficient to diagnose otosclerosis and other conditions that cause pulsatile tinnitus.
- The study by 1 highlights the importance of temporal bone CT scans in identifying changes of otospongiosis (otosclerosis) and other conditions that cause conductive hearing loss.
- The study by 1 provides an updated approach to diagnosing tinnitus, including the use of HRCT in evaluating pulsatile tinnitus.
Diagnostic Approach
- Otoscopy is extremely useful to guide the correct imaging in evaluation of otosclerosis.
- A diagnostic algorithm based on detailed history and clinical evaluation should progress from less invasive to more invasive imaging studies.
- HRCT of the temporal bone is the preferred imaging modality for diagnosing otosclerosis and other conditions that cause pulsatile tinnitus.
From the Research
Definitive Diagnostic Test for Otosclerosis
The definitive diagnostic test for otosclerosis is a subject of interest in the medical field, and various studies have been conducted to determine the most effective method.
- High-resolution computed tomography (HRCT) is considered the gold standard imaging modality for diagnosing otosclerosis, as it provides detailed images of the temporal bone and middle ear structures 2, 3, 4, 5, 6.
- HRCT has a high specificity of 95% and a positive predictive value of 92%, making it a reliable tool for diagnosing otosclerosis 2.
- A systematic checklist for diagnosing otosclerosis on HRCT has been developed, which includes looking for radiolucency at the fissula ante fenestram and pericochlear region, and new bone formation around the oval and round windows 4.
- The use of HRCT in diagnosing otosclerosis has been supported by various studies, which have demonstrated its effectiveness in detecting the disease and excluding other causes of hearing loss 3, 5, 6.
Key Findings
- HRCT is better at diagnosing the fenestral form of otosclerosis, but may be less effective in detecting inframillimetre, retrofenestral, and dense sclerotic lesions 2.
- The diagnosis of otosclerosis remains largely clinical, but HRCT serves as a useful adjunct to the clinician, helping to delineate the extent of disease and exclude other causes 2.
- Imaging prior to surgery aids in counseling patients, preparing surgically, and excluding other pathologies 4.
- CT densitometry and extent of disease on CT have been shown to correlate with hearing thresholds, and extensive and multifocal disease on CT has a poorer prognosis 6.