Hearing loss

Background

  • Sensorineural: involving the inner ear, cochlea, or auditory nerve
  • Conductive: any mechanical factor blocking external sound from gaining access to the inner ear; ex: cerumen impaction, middle ear fluid, ossicular chain fixation
  • Mixed: both sensorineural and conductive loss
  • Should evaluate for recent medication changes, family history of hearing loss, personal history of trauma, recent scuba diving or flying (barotrauma), cold water exposure, onset/progression of hearing loss, high- vs low-pitch loss, history of ear surgeries

Epidemiology

  • Most common causes: presbycusis, followed by noise-induced hearing loss
  • 90% of cases are due to Sensorineural hearing loss, 10% due to Conductive causes
  • Most bilateral cases that present gradually are benign. Sudden onset, unilateral hearing loss is more concerning for a serious cause.

Clinical Features

  • Varies by etiology

Differential Diagnosis

Sensorineural (Inner Ear)

Conductive

Evaluation

  • Whispered voice test: Stand at arm’s length behind the patient and block hearing in one ear by occluding the ear canal. Whisper a phrase and ask the patient to repeat it. Test both ears.
  • Tone-emitting otoscope: Designed to view the ear canal and TM while emitting three different screening levels at random intervals.

Weber test

  • Place a vibrating tuning fork on the forehead, equidistant to both ears
  • If the patient hears the sound equally in both ears, normal hearing or symmetric hearing loss is suspected.
  • If sound is heard more in affected ear → consider conductive hearing loss in affected ear
  • If sound is heard more in unaffected ear → consider sensorineural hearing loss in affected ear

Rinne test

  • A vibrating turning fork is placed on the mastoid bone behind the ear. When the sound is no longer heard, the fork is held near the ear canal.
  • If the sound is still present or louder at the ear canal, normal hearing is suspected. (i.e. Air conduction is greater than bone conduction)
  • If no sound is heard near the ear canal but the sound was still heard on the mastoid bone, conductive hearing loss is suspected in that ear. (i.e. bone conduction > air conduction)

Hum test

  • Hum test comparable to Weber test in diagnostic accuracy of new onset unilateral conductive hearing loss[1]
  • Hum test is conducted by asking the patient to hum and tell you in which ear the humming sounds louder
    • In sensorineural hearing loss, humming is louder in the unaffected ear
    • In conductive hearing loss, humming is louder in the affected ear

Pneumoscopy

  • To evaluate mobility of the TM.
  1. First, use positive pressure to force air into the EAC to push down the TM.
  2. Then, release the pressure and the negative pressure pulls the TM outwards.
    • Nonmobile = fluid in middle ear, mass in middle ear, stiff/sclerotic TM.
    • Hypermobile TM = ossicular chain disruption.
    • Movable TM only with negative pressure = blocked Eustachian tube.

Formal audiologic assessment

  • Outside scope of ED evaluation
  • Performed by an audiologist in a soundproof environment. Air and bone conduction are both tested.

Other tests

Consideration for these tests should be based on history and physical

  • Blood glucose
  • CBC to evaluate for anemia or infection
  • Thyroid testing
  • Serologic testing for Syphilis, Sjögren’s syndrome
  • CT scan for unexplained conductive hearing loss
  • MRI for sensorineural hearing loss
  • ENT evaluation for presbycusis

Management

  • Based on exam findings and imaging.

Disposition

  • Based on diagnosis

References

  1. Ahmed OH et al. Validity of the Hum Test, a Simple and Reliable Alternative to the Weber Test. Ann Otol Rhinol Laryngol. 2018 Jun;127(6):402-405.