#12135 - Hearing Loss - ENT

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 BC thresholds using bone conducting band are tested to differentiate sensorineural from conductive hearing loss

Tympanometry

• Tympanogram measures compliance of TM (pressure across the membrane)

• Useful in children who are often too young for other tests

Presbyacusis “Greek presbys “elder” + akousis “hearing”

Progressive degeneration of hearing in the auditory system leading to hearing impairment

Pathophysiology

• Peripheral (cochlea) and central (neural) degeneration

Clinical features

• Hearing impairment

• Threshold for hearing and uncomfortable level of sound are abnormally close

• Discrimination may also be affected e.g “I can hear you but I can’t understand you”

Investigations

• Pure tone audiogram shows high frequency loss

Management

• Hearing aids

Hearing loss in children

Hereditary

• Autosomal dominant

• Autosomal recessive

• Deafness = impairment to communication

• Children born with hearing loss have a major handicap to developing communication therefore early detection and management required for adequate speech and language...