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Medicine Notes ENT Notes

Hearing Loss Notes

Updated Hearing Loss Notes

ENT Notes

ENT

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Hearing Loss

Classification

  • Deafness = subjective decline in hearing acuity affecting one or both ears

  • Conductive hearing loss (“Obstructive”)

    • Pathology external or middle ear amenable to surgery

  • Sensory-neural hearing loss (“failure of transmission”)

    • Pathology affecting cochlear, auditory nerve or auditory centers in the brain

    • Often involves loss of hair cells from the Organ of Corti, therefore is usually permanent

Aetiology

Conductive hearing loss

  • External ear occlusion e.g wax, foreign body, congenital agenesis of the ear

  • Infection (otitis media/externa)

  • Glue ear

  • Trauma (direct blow, acoustic trauma)

  • Osteosclerosis – fixation of stapes on oval window (runs in families, associated with tinnitus and mild vertigo)

  • Iatrogenic (surgery)

Sensorineural hearing loss

  • Idiopathic

  • Presbycusis

    • Age-related hearing loss, usually loss of high-frequency sounds initially, because hair cells responding to high-frequency sounds are most easily damaged)

  • Viral infections (measles, mumps, meningitis)

  • Tumours affecting the cochlear nerve

  • Trauma – temporal bone fractures

  • Drugs – aminoglycosides e.g gentamycin

  • Central – brainstem CVA

Investigations

Tuning Fork Test

  • 512 Hz, middle C – so heard not felt)

  • Rinnes

    • Place tuning fork on mastoid bone and acoustic meatus and ask which is loudest (normally air conduction > bone conduction = positive Rinne’s test)

    • Negative test = pathology where bone conduction > air conduction = conductive hearing pattern

    • In sensorineural loss both AC and BC are decreased therefore AC should still be > BC

  • Webers

    • Place tuning fork in middle of forehead

    • Normal sound is equally loud in both ears

    • In unilateral conductive hearing loss the sound will lateralise to the affected side

Pure Tone Audiogram

  • Pateint sits in a sound-proof room

  • Earphones used for air conduction

  • Patient presses and holds button for as long as a sound is heard

  • Tests the following frequencies – 250, 500, 1000, 2000, 4000, 8000Hz

  • Sound intensity (dB) increased in 5dB increments until sound is heard (-10 to 110)

  • If AC thresholds are above 20dB then...

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