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Electrocochleography

Electrocochleography. Dr. Supreet Singh Nayyar, AFMC For more presentations, visit www.nayyarENT.com. Headings. Introduction Principles Recording techniques Interpretation Clinical applications. Introduction. Electrocochleography (ECochG)

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Electrocochleography

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  1. Electrocochleography Dr. Supreet Singh Nayyar, AFMC For more presentations, visit www.nayyarENT.com www.nayyarENT.com

  2. Headings • Introduction • Principles • Recording techniques • Interpretation • Clinical applications www.nayyarENT.com

  3. Introduction • Electrocochleography (ECochG) • Method for recording the electrical potentials of the cochlea • Stimulus-related • Often includes measurement of the whole nerve or compound action potential (AP) of the auditory nerve. www.nayyarENT.com

  4. Principles CM • An alternating current voltage that mirrors the waveform of the acoustic stimulus at low-moderate levels of stimulation • Generated predominantly by the outer hair cells • Phase and duration are stimulus dependent www.nayyarENT.com

  5. Principles • SP • A Direct Current generated predominantly by the outer hair cells • Seen as a DC shift in the CM baseline • Duration is dependent on the duration of the acoustic stimulus • Independent of stimulus phase www.nayyarENT.com

  6. Principles • AP • AC potential that represents the summed response of the synchronous firing of several thousand auditory nerve fibers • N1 and N2 are virtually the same components as waves I and II of the ABR • Independent of stimulus phase and duration. www.nayyarENT.com

  7. Principles • The normal SP duration is b/w 0.30 and 0.45 ms, and the absolute amplitude of the SP can range from 0.1mV to 1.0 mV • AP has a latency of 1.5 ms(1.3 ms to 1.7 ms) duration is normally between 0.80 ms and 1.25 ms, absolute amplitude can vary greatly, ranging from 0.6 mV to 3.0 mV  www.nayyarENT.com

  8. Principles • Normal SP/AP ratios generally range from 0.1 to 0.4 across subjects with a mean value of 0.25. • Graphic Angle Measurement (GAM) Technique  www.nayyarENT.com

  9. Recording techniques • There are two, general approaches for recording ECochG • Transtympanic (TT) • Extratympanic (ET) www.nayyarENT.com

  10. Recording techniques • Recording parameters www.nayyarENT.com

  11. Recording techniques •  The following suggestions are offered to help to reduce stimulus artifact • test subjects in sound booth with the examiner and AEP unit located outside of the booth; the windows of the booth should be shielded with a copper screen; • plug the AEP unit into an isolated electrical socket equipped with a true-earth ground; • use a grounded cable for the primary electrode (such cables are commercially available); • turn off lights in the testing room and unplug unnecessary electronic equipment (it also may be necessary to turn off the lights in the examiner room); • consider encasing the transducer in grounded Mu metal shielding. www.nayyarENT.com

  12. Interpretation • Normal electrocochleogram from the tympanic membrane to clicks presented in alternating polarity at 80 dB HL www.nayyarENT.com

  13. Interpretation • Normal electrocochleogram from the tympanic membrane to a 2,000 Hz toneburst presented in alternating polarity at 80 dB HL www.nayyarENT.com

  14. Clinical applications • Menieres’ disease/ Endolymphatic hydro • The reported incidence of an enlarged SP and SP/AP amplitude ratio in the general Meniere’s population is only approximately 60%-65%  www.nayyarENT.com

  15. Clinical applications • Enhancement of wave I • Wave I is absent in the conventional ABR tracings but recordable with the ECochG www.nayyarENT.com

  16. Clinical applications • Intraoperative monitoring of inner ear and auditory nerve status during surgeries • identification of anatomic landmarks (such as the endolymphatic sac) www.nayyarENT.com

  17. Clinical applications • Other applications • Estimation of hearing thresholds www.nayyarENT.com

  18. Thank you For more presentations, kindly visit www.nayyarENT.com www.nayyarENT.com

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