Chapter 36 - Hearing Aids, Implantables

Question 1

When to consider hearing aid

Answer 1

HL + difficulty communicating

Question 2

Indications for bone conduction HA

Answer 2

congenital malformation ext/mid ear
chronically discharging ear
single-sided deafness

Question 3

Four parts of hearing aid, and how acoustic feedback happens

Answer 3

mic, amplifier, receiver, battery
amplified sound leaks out receiver, back into mic
High pitched squeal
Occurs more often in high power HA, in the ear HA, open-fit, vented earmold.
Feedback can also be sign of problem with earmold

Question 4

Tx of single-sided deafness

Answer 4

CROS, bone HA headband/teeth/transcutaneous/percutaneous

Question 5

Which hearing aids are contraindications for MRI?

Answer 5

CI

fully implanted HA

Question 6

When it is okay to implant a CI in child <12 mo

Answer 6

Meningitis (bypass HA trial), due to possibility of cochlear ossification

Question 7

How hearing aid works

Answer 7

microphone picks up sound waves
converted to electrical signal by analog/dig converter
Microchip filters signal, manipulates sound
Signal converted back to analog
Analog signal sento to receiver, converted to acoustic signal that patient hears

Question 8

Loudness recruitment

Answer 8

As hair cells damaged, normal adjacent ones recruited to help hear that frequency and their own, causing their own frequency to be loud
rapid growth of loudness with increasing stimulus
Treat with wide dynamic range compression in HA

Question 9

CROS vs BiCROS

Answer 9

Use BiCROS if there is some hearing loss in the better ear, CROS if better ear is normal

Question 10

Two most common complications of percutaneous bone conduction HA

Answer 10

infection/inflammation
failure to osseointegrate
Longevity of device highly dependent on hygiene/care

Question 11

How transcutaneous bond cond HA stays in place

Answer 11

Device held in place by internal and external magnets

Question 12

How implantable hearing aid works

Answer 12

Vibrates ossicular chain directly

Disrupts the ossicular chain when implanted

Question 13

Challenges of implantable hearing aid

Answer 13

capacity, recharging ability of batteries
adequate middle ear space (less space = less possible gain)
cost
insurance
MRI contraind

Question 14

How cochlear implant works

Answer 14

Mic picks up sound, send to speech processor
processor digitally encodes sound
Coded signals sent up cable to coil, sends info across skin via FM radio to receiver (just under skin)
Receiver presents information to auditory nerve via electrodes in tiny electrical impulses
Impulses travel to brain

Question 15

Indications for CI

Answer 15

> 18 yr and bilateral moderate to profound HL, limited benefit from HA (<50% sentence recognition in ear to implant, <60% in other ear, or <40% binaurally aided)

2-17 and bilateral severe to profound SNHL, or limited benefit from HA (binaural amplification trial 6 mo with word recognition <30%)

1-2: bilateral prfound SNHL, no progress in auditory skills with binaural HA 3 mo

Question 16

Pre-CI workup for adult

Answer 16

Assess unaided thresholds, audio consult with CI audiologist, aided thresholds, speech discrimination, CT or MRI, VNG/VEMP

Question 17

When to use hybrid CI

Answer 17

near normal low frequency hearing

Question 18

Who performs well with CI

Answer 18

post-lingual deaf rather than prelingual
Short duration of deafness
Ear aided consistently and frequently
NL ear structure
Motivation pt and family
No other medical conditions

Question 19

Can malformed inner ears be given a CI?

Answer 19

Yes, not much trouble with Mondini or enlarged aqueduct, but more difficult surgery (although still possible) with common cavity

Question 20

Hearing aid for patients without an auditory nerve (ie NF22 post surgery)

Answer 20

Auditory Brainstem Implant

Question 21

Current situations where studies show benefit to CI but not FDA-approved

Answer 21

<12 mo (w/o meningitis)

single sided deafness