Stacked ABR

Question 1

Are rate study ABR and neurodiagnostic ABRs not good at detecting small tumors?

Answer 1

Yes
The reason why ABR does not identify small tumors can be explained by the fact that ABRs rely on latency changes of wave (peak) V
Wave V is primarily influenced by high-frequency fibers and tumors will be missed if those fibers aren’t affected by the lesion
Although the click stimulates a wide frequency region on the cochlea, phase cancellation of the lower frequency responses occurs as a result of time delays along the basilar membrane
If a tumor is small, it is possible those fibers won’t be sufficiently affected to be detected by the traditional ABR measure

Question 2

When was stacked ABR published as a way to enhance the sensitivity of the ABR detecting smaller tumors?

Answer 2

1997
Their hypothesis was that the new ABR-stacked derived-band ABR amplitude could detect small acoustic tumors missed by standard ABR measures
Described as an attempt to record the sum of the neural activity across the entire frequency region of the cochlea in response to a click stimuli

Question 3

What are stacked ABRs?

Answer 3

The stacked ABR is the sum of the synchronous neural activity generated from five frequency regions across the cochlea in response to click stimulation and high-pass pink noise masking

Question 4

Does stacked ABR look at amplitude changes instead of latency changes?

Answer 4

Yes
Need to look at changes in amplitude of the response from different frequency region

Question 5

Is the stacked ABR a sum of all of the amplitudes from difference frequency regions?

Answer 5

Yes
Compares wave V

Question 6

Are stacked ABRs practical in a clinical setting?

Answer 6

Not really
CE chirp replaced this

Question 7

What are the presentations of vestibular schwannomas?

Answer 7

Unilateral HL, sloping configuration, fair to poor speech discrimination with rollover
Normal OAEs (if internal auditory artery is not compressed and blood supply to cochlea is intact)
Abnormal reflexes (absent or decay)
Abnormal ABR (ipsi)
Abnormal MRI (even with small tumors)

Question 8

Do vestibular schwannomas grow fast?

Answer 8

No, most of the time they will choose to monitor them because they are not causing issues and aren’t progressing rapidly

Question 9

How to enhance wave I?

Answer 9

Use a tiptrode or TM electrode
Increase stimulus intensity
Slow click rate
Change polarity (rarefaction usually optimal)
Increase number of sweeps

Question 10

What are the presentations for neurofibromatosis II?

Answer 10

Bilateral HL, normal or rising configuration, poor speech discrimination with rollover
Normal OAEs
Abnormal reflexes
Abnormal ABR (bilateral) as tumors expand
Abnormal MRI

Question 11

What are the presentations for auditory neuropathy?

Answer 11

Normal hearing sensitivity to profound apparent SNHL
Rising configuration
Very poor speech discrimination even with normal audio
Normal OAEs
Normal cochlear microphonic in ECochG
Abnormal reflexes
Abnormal ABR (no response, including wave I)
Normal MRI bilaterally

Question 12

Is auditory neuropathy often a component of other peripheral neuropathies?

Answer 12

Yes
Hereditary sensory motor neuropathies (HSMN), e.g., Charchot-Marie-Tooth disease
Friedreich’s ataxia
Site of lesion in spiral ganglion cells or auditory nerve fibers (8th cranial nerve)

Question 13

Does the latency between clicks and CE chirps differ?

Answer 13

Yes
The CE chirps will generally have a shorter latency than clicks