How to investigate hearing loss?

Comprehensive Investigation of Hearing Loss

A systematic approach to investigating hearing loss should begin with a thorough family history, targeted patient history, physical examination, and appropriate audiometric testing, followed by specific diagnostic tests based on initial findings. 1

Initial Evaluation

Family History

• Construct a 3-generation pedigree with attention to:
  • Consanguinity and paternity
  • Hearing status of parents and siblings
  • Ethnicity and country of origin
  • Inheritance pattern (autosomal dominant, autosomal recessive, X-linked, mitochondrial)
  • Syndromic versus nonsyndromic features 1

Patient History

1. Audiometric characteristics:

   • Age of onset
   • Progression pattern (sudden, progressive, fluctuating, stable)
   • Laterality (unilateral vs bilateral)
   • Associated symptoms (tinnitus, vertigo, aural fullness) 1

2. Risk factors:

   • Prenatal: Maternal infections (CMV, rubella), illnesses, medications
   • Neonatal: Prematurity, hypoxia, hyperbilirubinemia, sepsis, ototoxic medications
   • Postnatal: Meningitis, head trauma, noise exposure, ototoxic drugs 1
   • History of aminoglycoside exposure (which can cause irreversible hearing loss) 2

Physical Examination

1. Otologic examination:

   • Inspect ear canals and tympanic membranes
   • Pneumatic otoscopy to assess tympanic membrane mobility
   • Remove cerumen impaction if present 1

2. Focused assessment for syndromic features:

   • Visual anomalies (heterochromia, retinitis pigmentosa, cataracts)
   • Facial/cervical dysmorphology (preauricular pits, branchial cysts, cleft palate)
   • Pigmentary changes (white forelock, premature graying)
   • Neurological abnormalities
   • Balance disturbances 1

3. Tuning fork tests:

   • Weber test: Place vibrating tuning fork (256 or 512 Hz) at midline of forehead
   • Rinne test: Compare bone to air conduction 1

Diagnostic Testing

Audiometric Assessment

• Complete air and bone conduction threshold testing
• Speech audiometry measures
• Otoacoustic emission (OAE) testing to assess cochlear function 3
• Determine type of hearing loss:
  • Conductive: Normal bone conduction with abnormal air conduction
  • Sensorineural: Both air and bone conduction affected
  • Mixed: Elements of both 4

Imaging Studies

• MRI with contrast of internal auditory canals for:

  • Asymmetric sensorineural hearing loss
  • Sudden sensorineural hearing loss
  • Suspected retrocochlear pathology (vestibular schwannoma) 3

• High-resolution CT scan of temporal bones for:

  • Suspected ossicular chain abnormalities
  • Conductive or mixed hearing loss
  • Malformations of the ear 3

Laboratory Testing

• Not routinely indicated unless systemic illness is suspected 4
• Consider testing for:
  • CMV in infants
  • Genetic testing based on clinical presentation 1

Diagnostic Algorithm Based on Hearing Loss Type

1. For Sudden Sensorineural Hearing Loss (≥30 dB within 72 hours)

• Immediate otolaryngology referral
• MRI with contrast
• Assess for neurologic symptoms 1

2. For Asymmetric Hearing Loss

• MRI with contrast of internal auditory canals
• Regular audiologic monitoring (repeat testing in 3-6 months) 3

3. For Suspected Syndromic Hearing Loss

• Genetic counseling
• Genetic testing (single-gene tests or hearing loss multigene panels)
• Additional organ system evaluations based on suspected syndrome 1

4. For Nonsyndromic Hearing Loss

• If simplex case (no family history):
  • CMV testing in infants
  • GJB2 (connexin 26) mutation screening
• If multiplex case (family history present):
  • Proceed directly to connexin 26 testing 1

Common Pitfalls to Avoid

1. Inadequate follow-up: Regular monitoring is essential to detect progression and ensure optimal management 3

2. Overlooking ototoxic medications: Many medications can cause or worsen hearing loss, including aminoglycosides, which can cause irreversible damage 2

3. Missing conductive causes: Always perform thorough otoscopic examination to rule out cerumen impaction, middle ear fluid, or other treatable conductive causes 1

4. Neglecting bilateral sudden hearing loss: This rare presentation requires urgent evaluation for specific underlying causes 1

5. Underutilization of hearing rehabilitation: Despite high prevalence of hearing loss, there are substantial gaps in utilization of amplification options 5

By following this systematic approach to investigating hearing loss, clinicians can establish an etiologic diagnosis and implement appropriate management strategies to improve patient outcomes and quality of life.