What is the initial investigation for a patient presenting with hearing loss?

Initial Investigation for Hearing Loss

The initial investigation for a patient with hearing loss must begin with pure tone audiometry (PTA) to distinguish sensorineural from conductive hearing loss and establish the severity, pattern, and laterality of hearing impairment. 1

First-Line Diagnostic Test: Audiometry

Pure tone audiometry is the gold standard for detecting and characterizing hearing loss and should be obtained as soon as possible, ideally within 14 days of symptom onset for sudden hearing loss. 1

Components of Comprehensive Audiometric Evaluation

A complete diagnostic audiometric evaluation should include:

• Pure tone audiometry (air and bone conduction) to measure hearing thresholds across frequencies and differentiate conductive from sensorineural hearing loss 1, 2
• Speech audiometry (speech reception thresholds and word recognition testing) to assess functional hearing ability 1, 2
• Tympanometry/immittance testing to evaluate middle ear function and rule out conductive pathology 2, 3
• Acoustic reflex testing as part of the comprehensive evaluation 1, 2

Critical Timing Considerations

• For sudden hearing loss (onset within 72 hours), audiometry must be obtained urgently within 14 days to confirm diagnosis and guide treatment 1, 4
• For gradual or chronic hearing loss, audiometry should still be obtained promptly rather than delayed, as early identification improves outcomes and prevents complications 1, 2

Essential Clinical Assessment Before or Concurrent with Audiometry

History Elements to Identify

• Onset and duration: sudden (within 72 hours) versus gradual 1, 5
• Laterality: unilateral, bilateral, or asymmetric 1, 5
• Associated symptoms: tinnitus, vertigo, otalgia, otorrhea, aural fullness, or focal neurological findings 1, 5
• Recurrent episodes of hearing loss or vertigo 1
• Ototoxic medication exposure 4

Physical Examination Priorities

• Otoscopic examination to identify cerumen impaction (potentially curative if removed), tympanic membrane abnormalities, or middle ear pathology 5, 4
• Cranial nerve examination, particularly CN VIII 5
• Auscultation of neck, periauricular, and temporal regions if pulsatile tinnitus is present 5

What NOT to Order Routinely

Strong Recommendations Against

• Do NOT order routine CT of the head/brain in the initial evaluation of presumptive sensorineural hearing loss 1
• Do NOT obtain routine laboratory tests (CBC, metabolic panel, autoimmune panels) unless systemic illness is specifically suspected 1

When to Obtain Additional Testing

Indications for MRI with Contrast or Auditory Brainstem Response

Obtain MRI with contrast (or auditory brainstem response if MRI contraindicated) when:

• Asymmetric or unilateral sensorineural hearing loss is documented on audiometry (to rule out vestibular schwannoma or retrocochlear pathology) 1, 2, 4
• Poor word recognition scores disproportionate to pure tone thresholds 1
• Focal neurological findings are present 1
• Pulsatile tinnitus is reported 2, 5

Specialized Testing for Specific Presentations

• Sound discomfort level testing should be added for patients reporting hyperacusis or noise intolerance 3
• Follow-up audiometry at conclusion of treatment and within 6 months for sudden sensorineural hearing loss 1

Common Pitfalls to Avoid

• Do not delay audiometry waiting for symptoms to persist 6 months—immediate testing is appropriate for unilateral symptoms or when clinically indicated 2
• Do not assume normal hearing based on patient self-report alone, as hearing loss may be unsuspected, mild, or fluctuating 2, 5
• Do not overlook cerumen impaction during otoscopy, as removal may be curative for conductive hearing loss 5, 4
• Do not miss asymmetric hearing loss, which mandates imaging to exclude retrocochlear pathology even if the patient perceives bilateral symptoms 2, 4, 6

Algorithmic Approach

1. Perform otoscopy → Remove cerumen if impacted
2. Obtain audiometry (PTA, speech testing, tympanometry, acoustic reflexes) within 14 days for sudden loss, promptly for gradual loss
3. Review audiogram for:
   • Type: conductive vs. sensorineural vs. mixed
   • Laterality: symmetric vs. asymmetric
   • Severity: mild, moderate, severe, profound
4. If asymmetric sensorineural hearing loss → Order MRI with contrast 1, 2, 6
5. If conductive or mixed loss → Refer to otolaryngology for surgical evaluation 1, 4
6. If symmetric sensorineural loss → Refer to audiology for hearing aid evaluation 1, 4