Lecture 23: Clinical assessment of hearing and intervention Flashcards
What are some outer ear sources of conductive hearing loss?
- Obstruction-Cerumen, foreign object
- Canal exostosis (Surfers ear)
- Atresia/stenosis
What are some middle ear sources of conductive hearing loss?
- Otitis media with effusion
- Cholesteatoma
- TM perforation
- Ossicular chain disruption
- Congenital malformation
Describe what is sensorineural hearing loss:
- Sensory hair cells damaged
- Some auditory nerves survive
- Damaged hair cells unable to transmit electrical impulses
- Auditory signals cannot be conveyed to the brain
- Loss of loudness, clarity and resolution of sound.
How can you determine where the central hearing disorder is?
Can use electrophysiology to determine where in the auditory pathway of the brain is damaged
- Distal cochlear nerve
- proximal cochlear nerve
- superior olivary complex
- lateral lemniscus
- Inferior colliculus
- Medial geniculate body
What are some behavioural hearing assessments?
Pure tone audiometry
- > Air conduction
- > Bone conduction
Modified for children
(Visual response, little kids)
(Conditioned play audiometry, babys)
World recognition assessment
What are the objective hearing assessment?
- Tympanometry
- Acoustic reflex threshold and decay
- Otoacoustic emissions (sounds emitted by cochlea)
- Evoked potentials assessments
- —> Auditory brainstem response (Hearing threshold, site of lesion)
- —> Cortical evoked potentials
Do humans hear equally across all frequencies?
Human ear is not equally sensitive across frequencies, adjusted for in audiograms
What are the hearing technologies?
- Hearing aids
- Bone conduction devices
- Cochlear implants
- Brainstem implants
- Other assistive technologies
What is a bone conduction device?
Bone conduction hearing aid: Wearable, removable
Useful for: Atresia, single-sided deafness
(Surgically placed in the temporal bone, hearing aid detects the sound and vibrates in the bone)
How do hearing aids work?
- Acoustically amplify sound through outer and middle ear to stimulate travelling wave in cochlea
- Outcomes rely on the responsiveness of surviving hair cells
How do cochlear implants work?
- Bypass damaged hair cells and stimulate the nerve directly
- Convert the acoustic input signal into an electrical pattern that is transmitted by FM signal through skin to internal device and delivered to electrodes in scala tympani
- Rely on surviving neural elements to be stimulated by direct delivery of current pulses
How does a auditory brainstem implant work?
Similar to cochlear implant except electrode is placed in the brainstem
What is the candidacy for adults for cochlear implants?
- Bilateral moderate to profound sensorineural hearing loss
- No max age
- Pts with additional needs not excluded
- Limited or no useful benefit from hearing aids
- 60% or less on CVC words in the better ear
What is the candidacy for children for cochlear implants?
- Children who have recently suffered from meningitis which has caused a sensorineural hearing loss should be referred urgently following diagnosis
- Bilateral severe hearing loss or worse, from 1khz to 8khz on ABR testing
- Limited aided speech information above 2khz. Severe reverse sloping hearing loss or worse, or those whose speech and language is not progressing adequately.
- Auditory neuropathy spectrum disorder who are not progressing in their speech and language development
Whats the incidence of hearing loss?
- Leading cause of disability worldwide
- Everyday encounters
What are the behavioural manifestations of hearing loss?
- Hearing/speech perception
- speech production
- language
- motor skills
- experiential/world knowledge
- literacy
- school achievement
- vocational/economic
- psycho/social emotional
- Cognition
What is rhines test?
Vibrating tuning fork placed against the mastoid and then when the sound can no longer be heard, turning it so the forks are near the ear. Because air conduction is better than bone therefore sound should still be able to be heard in the vibrating tuning fork.
It is indicative of middle ear issues / conductive issues. Sensorineural hearing loss will still differentiate air from bone conduction
What is the webbers test?
Tuning fork placed centrally atop skull. Lateralization to one side, that is louder on one side indicated sensorineural hearing loss in the opposite ear (quiter one). BUT bisensorineural hearing loss will not produce this difference. So could be a false positive.
BUT sound lateralises to the AFFECTED side in conductive hearing loss.
THEREFORE its important to do webbers and rhines together
