ABR

Question 1

What range of hearing does ABR test

Answer 1

1. 250 Hz - 1000 Hz

Question 2

What is the wave I site generator

Answer 2

Distal portion of the auditory pathway

Question 3

What is the wave II site generator

Answer 3

Proximal end of the auditory nerve

Question 4

What is the wave III site generator

Answer 4

Second order auditory neurons in the cochlear nuclei

Question 5

What is the wave IV site generator

Answer 5

The superior olivary complex

Question 6

What is the wave V site generator

Answer 6

Fibres of the lateral lemniscus as they enter into the inferior coliculus

Question 7

What are the stimuli for ABR threshold testing

Answer 7

Clicks and tone bursts

Question 8

Why are tone bursts better than clicks

Answer 8

Gives frequency specific results

Question 9

Strengths of ABR (2)

Answer 9

1. They are not affected by arousal
2. Resistant to sedatives
3. Tests between 250-1000 Hz

Question 10

Weaknesses of ABR (5)

Answer 10

1. Has a splatter effect and requires a filter
2. Results can be obscured by muscle movement
3. High level of variability
4. ABR won’t detect the loss between 6-8 kHz
5. Pass from ABR does not equal normal hearing

Question 11

How do you interpret ABR results

Answer 11

ABR results are 10-15 dB above the behavioural threshold

Question 12

How do you interpret ABR results (2)

Answer 12

1. ABR results are 10-15 dB above the behavioural threshold

2. If inserts are used, subtract .08

Question 13

What is ABR (2)

Answer 13

1. An electrical potential generated by a transient stimulus which generates synchronous firing of auditory neurons.
2. Its waves are measured by latency and amplitude.

Question 14

When do ABR waves occur

Answer 14

Within 15 ms after stimulus onset (short latency)

Question 15

How do you interpret latency (5)

Answer 15

1. Repeatability is required, not repeatable if wave V latency is <0.2 ms
2. Compare wave V latency between ears, abnormal if ILD >0.25 ms at 70 dBnHL
3. Asymmetry in ABR but not PTA
4. Interpeak latency (I-V) - abnormal if I-V interval peak .4.4 ms

Question 16

What are the disadvantages of calculating interaural latency differences (2)

Answer 16

1. Not applicable to patients with bilateral tumours

2. Not applicable when there’s poor morphology

Question 17

Magnitude of the amplitude depends on… (2)

Answer 17

1. Number of neural elements activated by the sound of stimulus
2. Degree of sychronisation of neural activity