What is the recommended workup and management for a patient with asymmetric sensorineural hearing loss?

Workup and Management of Asymmetric Sensorineural Hearing Loss

All patients with asymmetric sensorineural hearing loss require MRI with dedicated internal auditory canal protocol to exclude vestibular schwannoma, which is the standard of care regardless of clinical presentation. 1, 2

Define Asymmetry on Audiometry

Asymmetric sensorineural hearing loss is established when audiometry demonstrates any of the following: 2

• ≥10 dB interaural difference at 2 or more contiguous frequencies, OR
• ≥15 dB interaural difference at any single frequency 1, 2
• Alternative criteria include ≥15% difference in speech recognition scores or ≥15 dB difference at any 2 frequencies between 2000-8000 Hz 2

The ≥10 dB at 2 contiguous frequencies criterion is most sensitive for detecting pathology, while ≥15 dB specifically at 3000 Hz has the highest positive predictive value for identifying actual lesions on MRI. 1, 2

Immediate Triage: Rule Out Sudden Onset

If hearing loss developed within 72 hours, this is an otologic emergency requiring immediate action before imaging: 2

• Initiate oral corticosteroids immediately (prednisone 1 mg/kg/day, maximum 60 mg, for 7-14 days with taper) without waiting for MRI 2, 3
• Still obtain MRI within 14 days of symptom onset 2
• For treatment failures or patients presenting 2-6 weeks after onset, offer intratympanic steroid therapy (4-6 injections of dexamethasone 24 mg/mL over 2 weeks) 2, 3

The distinction between sudden and non-sudden onset fundamentally changes management, as sudden sensorineural hearing loss carries a 5.4% risk of vestibular schwannoma but requires immediate steroid therapy. 2

Mandatory Imaging Protocol

MRI with gadolinium contrast and dedicated internal auditory canal protocol is required for all cases of asymmetric sensorineural hearing loss: 1, 2

• Use high-resolution 3-D T2-weighted sequences with thin sections across the internal auditory canal and inner ear 2
• Include evaluation of brainstem and thalami 2
• Gadolinium contrast facilitates visualization of vestibular schwannomas, meningiomas, labyrinthitis, and neuritis 2

The diagnostic yield for vestibular schwannoma is significant enough that MRI screening is recommended for patients meeting the audiometric criteria above, though selectively screening those with ≥15 dB difference at 3000 Hz alone may minimize unnecessary MRIs. 1

Alternative Imaging in Specific Scenarios

Obtain CT temporal bone instead of (or in addition to) MRI when: 2

• History of head trauma precedes the hearing loss
• Need to evaluate for temporal bone fractures or inner ear anatomic abnormalities 2

Do NOT order routine CT head in the initial evaluation unless focal neurologic findings are present. 3

Serological Testing: Only When Clinically Indicated

Order serological tests only when specific conditions are suspected by history and physical examination: 2, 3

• Lyme disease serology in endemic areas 2
• Syphilis testing (FTA-abs) if multiorgan involvement or fluctuating bilateral symptoms 1, 2
• HIV testing if risk factors present 2
• Autoimmune inner ear disease markers if fluctuating hearing loss 1, 2

Do NOT obtain routine laboratory tests in patients with asymmetric sensorineural hearing loss, as this adds cost without benefit. 3

Specialist Referral

Refer all patients to otolaryngology after audiometry establishes the diagnosis of asymmetric sensorineural hearing loss. 2

Audiologic Rehabilitation

Begin audiologic rehabilitation as soon as hearing loss is identified: 2

• Refer to audiology for hearing aid evaluation and fitting 1, 2
• Address impacts on communication, sound localization, safety, and quality of life 1, 2
• For unilateral impairment, consider contralateral routing of signal (CROS) hearing aids or bilateral CROS (BiCROS) if pre-existing hearing loss in better ear 1
• Counsel patients about support groups such as Hearing Loss Association of America 1

86% of adults with unilateral sudden sensorineural hearing loss report hearing handicap, and 56% with tinnitus demonstrate handicap on validated inventories. 1

Follow-Up Monitoring

Obtain follow-up audiometry at conclusion of any treatment and within 6 months: 2

• Assess for changes and adjust management accordingly 2
• Continue monitoring for patients with residual hearing loss or tinnitus 1, 2

Critical Pitfalls to Avoid

• Do not delay MRI imaging based on low clinical suspicion—vestibular schwannomas can present with isolated asymmetric hearing loss without other neurologic symptoms 1, 2
• Do not assume bilateral sudden sensorineural hearing loss is idiopathic—this presentation mandates evaluation for meningitis, autoimmune disease, Lyme disease, syphilis, or ototoxic medications 1, 3
• Do not wait for imaging results before initiating steroids if hearing loss occurred within 72 hours 2
• Do not rely on acoustic reflex testing or rollover as screening tools, as they have high false-negative rates for retrocochlear pathology 4