Wk6c-Auditory Brainstem Implants

Question 1

What are the characteristics of an ABI (Auditory Brainstem Implant) candidate?

Answer 1

Individuals with a non-functioning auditory nerve (e.g. NF2)

Question 2

Where is the electrode array placed for an ABI?

Answer 2

On the exposed surface of the cochlear nucleus

Question 3

What is Neurofibromatosis?

Answer 3

A genetic disorder that causes tumours to grow on nerve tissue

• Type II usually causes symmetrical non-malignant tumours on the vestibulocochlear cranial nerve (aka. Vestibular schwannoma); can cause HL, tinnitus, and balance issues
• *Nerve is affected, not the inner ear

Question 4

In an ABR, waves 1-V are associated with which parts of the auditory pathway?

Answer 4

I - distal cochlear nerve
II - proximal cochlear nerve
III - cochlear nucleus
IV - SOC
V - lateral lemniscus

Question 5

Where is the tumour usually located with NF2?

Answer 5

Wave II - the distal portion of the cochlear nerve
- this means we must stimulate the AN above this location at level of cochlear nucleus (Wave III area) provided that everything above this is functioning

Question 6

ABIs were first developed in ____ and consisted of two ball electrodes that were implanted near the surface of the cochlear nucleus.

Answer 6

1979

Question 7

The current ABI versions use 21- and 12-electrode surface arrays and which sound processing strategies?

Answer 7

SPEAK and CIS

Question 8

How do current ABI electrodes differ from CI electrodes?

Answer 8

Flat surface array compared to a curved electrode

Question 9

True or False: ABI users perform similarly to CI users regarding speech understanding

Answer 9

False: ABIs only provide users with sound awareness and an average 30% improvement in speech understanding WHEN COMBINED WITH LIP READING
- ABI users average performance for simple sentences in quiet is around 10% compared to 80 for CI users

Question 10

What does PABI stand for?

Answer 10

Penetrating Auditory Brainstem Implant

• experimental penetrating array
• similar to ABI, but deeper penetrating electrodes at different lengths

Question 11

Did Shannon’s research show improvement in performance in speech in quiet for PABI compared to ABI?

Answer 11

No - similar averages, but no high-performing outliers with PABIs (compared to ABIs)
- ABI users without a tumour (non-NF2) did better on average, but results were very scattered

Question 12

ABI treatment is generally much ___ (less/more) successful than CI

Answer 12

Less - likely b/c not as tonotopically placed as CI, and programming is more challenging d/t limited processing abilities

Question 13

Why might the few non-NF2 patients do better with implantation?

Answer 13

Possibly d/t less damage to the nucleus

Question 14

What is an AMI?

Answer 14

Auditory Midbrain Implant - an electrode that is placed at the inferior colliculus

• very early in clinical trials
• 5 patients in 2016 - awaiting results

Question 15

How does an AMI work?

Answer 15

A few mm long
20 electrode contacts
- penetrates inferior colliculus
- Central IC has clear tonotopic organization (but is VERY hard to hit)
- array provides direct neural stimulation

Question 16

When the surgery is successful, AMI performance is _____ (worse than/similar to/better than) ABI

Answer 16

Similar to ABI, but still below CI performance

Question 17

AMI performance improved when combined with _____ ______

Answer 17

Lip Reading