NRI Overview

Question 1

What is NRI used for

Answer 1

• estimate psychophysical levels
• verify patient’s levels
• assess auditory nerve’s response to electrical stimulation
• as a counseling tool
• determine auditory nerve is responsive
• establish a baseline
• to assist with programming
• to provide reassurance to family or recipient (that nerve is functioning)

Question 2

What is NRI?

Answer 2

• measurement of Electrically Evoked Compound Action Potential (ECAP) using the system’s telemetry and intracochlear electrodes
• Most commonly used objective measure in the clinic

Question 3

What is AP

Answer 3

• action potential

* a small change in voltage resulting from the firing of nurons

Question 4

What is CAP

Answer 4

• the synchronous firing of neurons creates Compound Action Potential

Question 5

NRI vs. ABR

Stimulus Type

Answer 5

• NRI: electrical

* ABR: acoustical

Question 6

NRI vs. ABR

electrodes

Answer 6

• NRI: intracochlear

* ABR: skin surface

Question 7

NRI vs. ABR

Averaging

Answer 7

• NRI: 128
• ABR: >1000

(how many times you have to run this before you get a clean, non-changing signal)

Question 8

NRI vs. ABR

Sedation

Answer 8

• NRI: No

* ABR: Yes

Question 9

NRI vs. ABR

Benefits

Answer 9

• NRI: verify neural functioning an assist in programing

* ABR: estimate hearing level

Question 10

ECAP consists of which peaks

Answer 10

Negative peak (N1) followed by positive peak (P2)

Question 11

N1 latency

Answer 11

typically between 0.2-0.5ms

Question 12

P2 latency

Answer 12

typically less robust

latency occurring before ~1ms

Question 13

amplitude of response between N1 and P2

Answer 13

measured in uV (microvolts)

varies from 20-1500 uV

Question 14

What is tNRI?

Answer 14

NRI threshold

Where we measure/estimate the threshold to be

Question 15

Advantages of tNRI

Answer 15

• faster and easier to measure
• less contaminated by noise floor
• less subject among clinicians

Question 16

Limitations of tNRI

Answer 16

• too few data points can result in an inaccurate regression line (but this is preventable)

Question 17

NRI advantages

Answer 17

• predictor of audibility
• doesn’t require use of additional equipment
• easy to record in a relatively short period of time
• doesn’t require sedation

Question 18

Limitations of NRI

Answer 18

• doesn’t provide info for higher level functioning (peripheral level only)
• cannot be conducted on C1 patients
• not always present