Management of Asymmetrical Hearing Loss
All patients with asymmetric sensorineural hearing loss require MRI of the internal auditory canals to exclude retrocochlear pathology, particularly vestibular schwannoma or meningioma, as this represents the standard of care for identifying potentially treatable lesions. 1
Initial Diagnostic Approach
Define Asymmetry
Asymmetric sensorineural hearing loss is defined by any of the following criteria 1:
- ≥15 dB difference at 2 or more frequencies
- ≥15% difference in speech recognition score
- ≥20 dB difference at 2 contiguous frequencies
- ≥15 dB difference at any 2 frequencies between 2000-8000 Hz
Distinguish Type of Hearing Loss
First, determine whether the hearing loss is conductive, sensorineural, or mixed through complete audiometric evaluation including air and bone conduction thresholds, speech audiometry, and otoacoustic emissions 2. Conductive hearing loss from cerumen impaction, tympanic membrane perforation, middle ear effusion, cholesteatoma, or otosclerosis requires otolaryngology referral for potential surgical correction 1.
Mandatory Imaging Workup
When to Order MRI
MRI with gadolinium of the internal auditory canals and posterior fossa must be obtained for all cases of asymmetric sensorineural hearing loss 1, 3. This is non-negotiable because:
- Vestibular schwannomas and meningiomas can only be reliably detected with MRI 1, 2
- Early detection allows for hearing-preserving treatment when tumors are small 3
- All retrocochlear lesions are associated with abnormal findings on imaging 4
Alternative Imaging
If MRI cannot be performed due to contraindications, auditory brainstem response (ABR) testing serves as a less expensive screening tool, though it has lower specificity 2. High-resolution fast spin-echo or gradient-echo MRI without gadolinium is acceptable but requires specialized radiologic expertise 3.
Additional Imaging Considerations
If there is history of head trauma prior to hearing loss onset, obtain CT temporal bone to evaluate for fractures or inner ear anatomic abnormalities 1.
Time-Sensitive Scenarios
Sudden Sensorineural Hearing Loss (SSNHL)
If hearing loss developed within 72 hours, this is an otologic emergency 1:
- Initiate oral corticosteroids immediately 1, 2
- MRI should be performed within 14 days of symptom onset 3
- For treatment failures or patients presenting 2-6 weeks after onset, offer intratympanic steroid therapy 1
- All SSNHL cases still require imaging to rule out retrocochlear pathology 1
Additional Laboratory Testing
Order serological tests only when specific conditions are suspected by history 1:
- Syphilis serology if risk factors present 4
- Lyme disease testing in endemic areas 1
- HIV testing if risk factors present 1
- Autoimmune panels if autoimmune inner ear disease suspected 1
Avoid routine thyroid function testing as it provides little diagnostic value 4.
Specialist Referral
Refer to otolaryngology for 1:
- All cases of asymmetric sensorineural hearing loss after audiometry confirms the diagnosis
- Any conductive hearing loss component requiring surgical evaluation
- Poor word recognition (monosyllabic word score ≤60%) 1
- Abnormal imaging findings
Audiologic Rehabilitation
Hearing Amplification Options
Once retrocochlear pathology is excluded and any acute treatment completed 1:
- Traditional hearing aids are first-line management for residual hearing 2
- Contralateral routing of signal (CROS) hearing aids for unilateral impairment 1
- Cochlear implantation for severe to profound bilateral loss when hearing aids provide insufficient benefit 2
- Bimodal stimulation (cochlear implant in worse ear, hearing aid in better ear) provides superior outcomes compared to monaural amplification in asymmetric cases 5
Timing of Rehabilitation
Begin audiologic rehabilitation as soon as hearing loss is identified to prevent auditory deprivation and poorer outcomes 2. Delay in rehabilitation leads to worse functional results 2.
Patient Counseling
Address the following impacts on quality of life 1:
- Difficulty with conversation on the affected side and in noisy environments 1
- Inability to localize sound, creating safety risks for accidents 1
- Potential for dizziness and tinnitus if present 1
- Cognitive and emotional consequences of hearing impairment 1
- Need for hearing aids or assistive devices 1
For patients with residual hearing loss and/or tinnitus after treatment, counsel about benefits of audiologic rehabilitation and supportive measures 1.
Follow-Up Monitoring
- Obtain follow-up audiometry at conclusion of any treatment and within 6 months 2
- Regular monitoring to assess for changes and adjust management 2
- For SSNHL, improvement of ≥10 dB in pure tone thresholds or ≥10% in word recognition score constitutes meaningful recovery 1
Common Pitfalls to Avoid
Do not assume asymmetric hearing loss is simply age-related or noise-induced without imaging 1, 6. Age-related hearing loss should be symmetric, and asymmetry warrants investigation 1. Despite extensive testing, the etiology remains unclear in the majority of cases, but excluding treatable causes is essential 1, 4.