Wk6c-Auditory Brainstem Implants Flashcards
What are the characteristics of an ABI (Auditory Brainstem Implant) candidate?
Individuals with a non-functioning auditory nerve (e.g. NF2)
Where is the electrode array placed for an ABI?
On the exposed surface of the cochlear nucleus
What is Neurofibromatosis?
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
In an ABR, waves 1-V are associated with which parts of the auditory pathway?
I - distal cochlear nerve II - proximal cochlear nerve III - cochlear nucleus IV - SOC V - lateral lemniscus
Where is the tumour usually located with NF2?
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
ABIs were first developed in ____ and consisted of two ball electrodes that were implanted near the surface of the cochlear nucleus.
1979
The current ABI versions use 21- and 12-electrode surface arrays and which sound processing strategies?
SPEAK and CIS
How do current ABI electrodes differ from CI electrodes?
Flat surface array compared to a curved electrode
True or False: ABI users perform similarly to CI users regarding speech understanding
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
What does PABI stand for?
Penetrating Auditory Brainstem Implant
- experimental penetrating array
- similar to ABI, but deeper penetrating electrodes at different lengths
Did Shannon’s research show improvement in performance in speech in quiet for PABI compared to ABI?
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
ABI treatment is generally much ___ (less/more) successful than CI
Less - likely b/c not as tonotopically placed as CI, and programming is more challenging d/t limited processing abilities
Why might the few non-NF2 patients do better with implantation?
Possibly d/t less damage to the nucleus
What is an AMI?
Auditory Midbrain Implant - an electrode that is placed at the inferior colliculus
- very early in clinical trials
- 5 patients in 2016 - awaiting results
How does an AMI work?
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
