Middle Latency Response

Question 1

Describe recording parameters of the MLR.

Answer 1

• Electrode montage: A1, A2, C3, C4, Fpz (C3 and C4 go over temporal lobes)
• Normal variability: lots
• Patient state: awake
• Filtering: restrictive filter settings may result in false peaks
• Effects of level: delayed peak latencies and decreased amplitudes with reduced level

Question 2

How can you discriminate postauricular muscle (PAM) artifact and true MLRs?

Answer 2

• PAM artifact encroaches on the MLR (before 20 ms)

- Pa, however, occurs after 20 ms

Question 3

Describe sleep effects on the MLR.

Answer 3

• Only get a response in REM sleep but how do you know if the person is in REM sleep?
• Therefore, listener should be awake

Question 4

How can the MLR be analyzed?

Answer 4

• Ear effects

- Electrode effects

Question 5

What are the formulas for ear effects?

Answer 5

(A1-C3 + A1-C4)/2

(A2-C3 + A2-C4)/2

Question 6

What are the formulas for electrode effects?

Answer 6

(C3-A1 +C3-A2)/2

(C4-A1 + C4-A2)/2

Question 7

Describe the procedures used in Wihing et al. (2012).

Answer 7

• Click: 70 dB nHL, 9.8 clicks/s, presented separately to right and left ears
• Online filters: 20-1500 Hz
• Offline filters: 20-200 Hz
• Recommend 50% reduction in amplitude of ear or electrode effect

Question 8

Describe the important findings in Wihing et al. (2012).

Answer 8

• High detectability of MLR: 100% of NH children have measurable Na-Pa bilaterally
• Within-group variability smaller for relative (ear and electrode effects) than for absolute amplitude measures
• Electrode effect variance was smaller than the ear effect variance

Question 9

How is the MLR superior to the ABR?

Answer 9

• Measuring low-frequency hearing thresholds

- MLR is less dependent than ABR on neural synchrony (less phase cancellation)

Question 10

Describe effects of language-based learning impairment on MLR.

Answer 10

-Pa latency is significantly delayed in children (8-12) with LD compared to children with NH

Question 11

Describe MLR in patients with cortical lesions.

Answer 11

-All normal

Question 12

What are some important points with MLR?

Answer 12

• Head injury may lead to APD
• Deficits may be subtle (only detected with central auditory testing)
• Deficits may be amenable to remediation