hearing loss

  • 5% of world population has hearing loss and deafness
    • very common
    • being born with congenital deafness
    • conditions that cause deafness
  • the experience of hearing loss is extremely varied
    • it is either in the nerve
    • or out in the ear
  • the common place where damage occurs is the inner ear
  • depends on what age the individual loses their hearing
    • congenital deafness (born deaf - 5 yr - 10 yr - 20s - 80s)
    • therapeutic intervention
    • quality of hearing before loss and after loss
  • cochlear implants work only if hearing was lost after learning how to hear in adolescence and teenage
    • doesn’t not impart hearing to a person born blind
  • signing is a different mode of communication from spoken and heard language

causes of hearing loss

mutations during formation

  • many molecules that are involved in forming
    • the inner ear
    • the fluid of the cochlea
    • membranes of the cochlea
  • if a mutation occurs in any of the molecules
    • results in hearing loss or deafness

toxic medication

  • certain antibiotics and chemo-theraputic prescription drugs
    • are toxic to hair cells

presbyacusis

  • presbyacusis is loss of outer hair cells
    • very common with older people
    • intact inner hair cells, but cochlear amplifier is lost
  • the world is getting louder - sound pollution has considerably increased
    • the ear is designed for below 80 dB range
    • and only occasional exposure to above 80 dB range
    • in modern life, this has been flipped
    • the “occasional exposure” to above 80 dB range has become the norm
    • so presbyacusis sets in faster and in more people

presbyacusis

  • two types of hearing problems
    • conductive
    • sensorineural

conductive

  • problems with conducting the sound
    • through the external ear
    • through the tympanic membrane, in through the middle ear ossicles
    • and the stapes moving back and forth

possible causes

  • earwax fill-up
  • the tympanic membrane can burst
    • by pressure build up due to infection in the closed system
    • usually heals, else has to be replaced with tympanoplasty
  • otosclerosis (otospongiosis)
    • incomplete sound transfer due to sponginess
    • weber (top middle head bone) and rinne (bone below the ear) tests with a tuning fork
      • bone hearing vs air hearing

sensorineural

  • when nothing is wrong per conductive test results
    • person is sent to an audiogram test
  • in a person with hearing loss
    • the sound amplitude has to increase as the sound frequency increases
    • has to be closer to 120 dB for 8000 Hz sound frequencies
  • this happens because of loss of outer hair cells
  • if there are no hair cells left
    • cochlear implants are used
    • these implants trigger different parts of the cochlea based on the sound received
    • even a few trigger points used will do the trick

supplementary