ECochG

Question 1

Generation site of ECochG

Answer 1

Peripheral potentials generated from the cochlear and the auditory system

Question 2

What are the potentials (3)

Answer 2

1. Cochlear microphonic (CM)
2. Summating potential (SM)
3. Action potential

Question 3

How are cochlear microphonics (CM) generated (2)

Answer 3

1. Generated by deflection of the basilar membrane in response to a sound
2. Reticular lamina and OHC

Question 4

What are the properties of CM

Answer 4

EchoG CM occur before the ABR, with single polarity stimulus the wave appears with a single peak either positive (condensation) or negative (rarefaction).

Question 5

Interpretation of CM

Answer 5

Absence of CM at 60 dBnHL indicates significant cochlear damage

Question 6

How are summating potentials (SP) generated (2)

Answer 6

1. Inner Hair Cells

2. It is a direct current potential

Question 7

What are the properties of an SP

Answer 7

Polarity may be positive or negative depending on stim frequency, intensity and electrode placement

Question 8

Interpreting SP results

Answer 8

SP amplitudes are enlarged in Meniere’s

Question 9

Compound AP site of generation (4)

Answer 9

1. auditory nerve
2. same as ABR wave I
3. Summed response from never fibres located at the basal end of the cochlea
4. Strongest respons eis illicited from clicks