TypesConductive hearing lossSensorineural hearing loss
PathophysiologyExternal or middle ear pathology that disrupts conduction of sound into the inner earInner ear, cochlear, or auditory nerve pathology that impairs neuronal transmission to the brain
Clinical featuresHearing improves in noisy environments
Volume of voice remains normal because inner ear and auditory nerve are intact
Sound normally is not distorted
Features of external auditory canal pathology (e.g., cerumen impaction) are present.
Hearing worsens in noisy environments
Volume of voice may be loud because nerve transmissions are impaired
Tend to lose higher frequencies preferentially, such that sounds may be distorted
Often associated with tinnitus
Features of external auditory canal pathology are absent.
Speech audiometryNo discrimination loss.Discrimination loss is common.
AudiogramDifference between air and bone conductionHearing loss for higher frequency sounds.
Impedance audiometryElevated acoustic reflex thresholdNormal acoustic reflex threshold

Subtypes and variants


Presbycusis

  • Definition: age-related, sensorineural hearing loss
  • Pathophysiology: progressive and irreversible damage of the hair cells of the organ of Corti (especially near the basal turn of the cochlea) that impairs high-frequency hearing
  • Epidemiology
    • Most common cause of sensorineural hearing loss
    • Age 75: > 50%
    • Age 90: nearly 100%
  • Clinical features
    • Progressive bilateral hearing loss, particularly of higher frequencies (using a low-pitched and clear voice to speak with older patients can improve communication)
    • Difficulty hearing in noisy, crowded environments.
    • Can cause depression and/or isolation

Noise-induced hearing loss (NIHL)

  • Definition: hearing loss due to continuous exposure to sounds > 85 dB (e.g., during construction work, mining, welding) or a single exposure to sounds > 120 dB (e.g., gunshots, jet engines, fireworks)
  • Pathophysiology
    • Repeated or constant exposure to noise > 85 dB → cumulative microtrauma and irreversible damage to the stereocilia of hair cells of the organ of Corti → sensorineural hearing lossPasted image 20250324150501.png
    • Sudden noise > 120 dB → tympanic membrane rupture → conductive hearing loss
  • Clinical features
    • Slowly progressive hearing loss, beginning with loss of high-frequency hearing
    • Difficulty hearing in noisy, crowded environments
    • Difficulty hearing high-pitched voices (e.g., children’s) occurs as the condition progresses.
  • Treatment
    • There is no definitive treatment.
    • Hearing aids or cochlear implants
  • Prevention: hearing protection (i.e., earplugs or earmuffs)

Diagnostics


Treatment