From the Guidelines
The initial workup for conductive hearing loss should include a comprehensive history and physical examination, audiometric testing, and imaging with CT temporal bone without IV contrast as the first-line imaging modality. This approach is based on the most recent and highest quality evidence, including the American College of Radiology (ACR) Appropriateness Criteria for hearing loss and/or vertigo 1. The CT temporal bone without IV contrast is preferred for evaluating middle ear structures, ossicular chain, and mastoid, and for identifying changes of otospongiosis (otosclerosis), ossicular erosion or fusion, round window occlusion, and dehiscence of the superior semicircular canal.
Key components of the workup include:
- Comprehensive history and physical examination, including otoscopy to visualize the ear canal and tympanic membrane
- Audiometric testing, specifically pure tone audiometry, speech audiometry, and tympanometry to confirm the conductive nature of the hearing loss and quantify its severity
- Tuning fork tests (Weber and Rinne) to distinguish between conductive and sensorineural hearing loss
- Imaging with CT temporal bone without IV contrast as the first-line imaging modality
- Laboratory testing, such as complete blood count, erythrocyte sedimentation rate, and specific serologies, if systemic diseases are suspected
- Culture and sensitivity testing of ear drainage, if chronic otitis media or cholesteatoma is suspected
The use of CT temporal bone without IV contrast is supported by the ACR Appropriateness Criteria, which states that "CT temporal bone without IV contrast is the first-line imaging modality in patients presenting with acquired conductive hearing loss without any mass lesion seen within the middle ear cavity" 1. Additionally, the evidence suggests that IV contrast is not beneficial for evaluation of temporal bone in patients with conductive hearing loss, as the density of temporal bone and the small size of individual structures of interest, such as ossicles, are only evident on bone windows 1.
From the Research
Conductive Hearing Loss Workup
The workup for conductive hearing loss involves a thorough history, complete examination, and various diagnostic tests. The following are some of the key components of the workup:
- A thorough history to identify potential causes of conductive hearing loss, such as ear disease or trauma 2
- Complete examination, including audiometric testing and radiographic evaluation when necessary 2
- Otoscopy to visualize the tympanic membrane and external ear canal 3
- Tympanometry to assess middle ear function 3
- Nasopharyngoscopy to evaluate the Eustachian tube and nasopharynx 3
- Computed tomography (CT) scan of the temporal bone to evaluate the middle ear and inner ear structures 4
Diagnostic Tests
The following diagnostic tests may be used to evaluate conductive hearing loss:
- Audiometry to assess hearing thresholds and identify the type and degree of hearing loss 2, 5
- Video pneumatic otoscopy (VPO) to evaluate the movement of the tympanic membrane and diagnose conditions such as fixation of the malleus or incus 5
- OtoScan laser-assisted myringotomy (LAM) to make a circular and non-hemorrhagic perforation in the tympanic membrane and inspect the middle ear pathology 6
- Transtympanic endoscopy to visualize the ossicular chain and diagnose conduction disturbances 6
Special Considerations
In certain cases, such as patients with severe brain injury, conductive hearing loss may be caused by reversible and treatable impairments, such as middle ear effusion or cerumen impaction 3. Routine otoscopic examination and treatment, if required, can have rehabilitating and general health benefits.