ECochG – Electrocochleogram

  • Electrical responses of the cochlea and auditory nerve to acoustic stimulation
    • Involves recording from the external auditory meatus
    • When recording ECochG it is best to stimulate using rarefaction of condensation clicks.
    • Cochlea is recruited when there is an abnormal sensation of loudness
  • SP – Summation Potential
  • CM – Cochlear Microphonics
  • AP – Auditory Nerve Compound Action Potential, the whole nerve AP is generated by primary auditory nerve fibers

ECoG – recording off the brain

 

AS = Left Ear

AD = Right Ear

SL – Sensation Level

  • 60 above threshold = total dB

HL – Hearing Level

SPL – Sound wave pressure to ear in dB

Example:

  • HL = 20 dB
  • SL = 80 dB
  • SPL = 0 (+20) = 20SPL
  •              20 (+20) = 40 SPL

If the patient’s threshold (HL) is unknown, stim at 90 dB and increase and decrease by 3 dB to look for changes.

90dB+ 3db =93 dBNo change
90dB-3dB =87 dBNo change
87dB-3dB =84 dBNo change
84dB-3dB =81 dBSmaller

Run the test at 84dB

 

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