Lecture 12 - clinical disorders of the auditory system

Question 1

What are the 2 types of hearing loss?

Answer 1

1. conductive
2. sensorineural

Question 2

Where in the ear does conductive hearing loss affect?

Answer 2

ear canal
middle ear

Question 3

Where in the ear does sensorineural hearing loss affect?

Answer 3

cochlea
auditory nerve

Question 4

Describe the 2 types of noise induced hearing loss.

Answer 4

1. acoustic trauma - minority of cases - a single loud sound.
2. acoustic overexposure - prolonged exposure to moderately loud sounds - duration to cause damage inversely related to sound intensity.

Question 5

Describe cochlear synpatopathy.

Answer 5

• can occur with a normal audiogram
• selective damage to high SR fibres from noise overexposure
• effects on speech in noise
• diminished wave I of ABR

Question 6

What are the 3 types of age-related hearing loss (presbycusis).

Answer 6

1. metabolic - degradation of cochlear wall
2. sensory - high frequency slope
3. auditory nerve - not reflected in audiogram, diminished wave I of ABR and like cochlear synaptopathy.

Question 7

What is homeostatic plasticity?

Answer 7

compensation for hearing loss - restoring the magnitude of the reduced input signal.

Question 8

What are the 4 things homeostatic plasticity can include?

Answer 8

1. loudness recruitment - begins in the cochlea, occurs at higher levels
2. central gain - applied in order to correct the reduced input from external sounds but also acts on internal noise
3. central noise
4. tonotopic map changes - where hearing loss is most marked

Question 9

What is increased reliance on predictions and memory?

Answer 9

compensation for hearing loss - in sensorineural HL there is a reduced flow from the auditory cortex compared to an increased flow to auditory cortex

Question 10

What are 4 clinical disorders resulting from hearing loss?

Answer 10

1. tinnitus
2. musical hallucinosis
3. hyperacusis
4. dementia

Question 11

What are the brain mechanisms of tinnitus?

Answer 11

• central gain (or lack of)
• central noise
• filling in from auditory memory
• altered auditory predictions
• spontaneous activity in the auditory pathway
• increased by hearing loss
• brain must decide whether to accept this as a signal or ignore it
• once accepted, the brain learns to predict tinnitus - hence remains

Question 12

What are some treatments for tinnitus?

Answer 12

• restoring hearing with hearing aids, cochlear implants etc
• medications to treat anxiety/depression
• sound generator to mask the sound
• psychological retraining techniques

Question 13

What is the difference between tinnitus and musical hallucinosis?

Answer 13

greater involvement with areas involved in rhythm and melody processing

Question 14

What is hyperacusis?

Answer 14

-experience of moderately loud sounds as uncomfortably loud