A&P Quiz 5 Deck 3: Acquired Inner Ear Pathologies (NIHL, Presbycusis, Meniere's)

Define acquired causes of hearing loss

Causes that result in hearing loss later in life

List the six acquired causes of hearing loss

• Infections

• Aging

• Diseases

• Trauma

• noise/music induced damage

• ototoxic drug-induced damage

Define prelingual hearing loss and its goal

• Loss occurs before language develops

• Goal (for kids): give access to language for learning

Define perilingual hearing loss

Hearing loss while language is developing

Define postlingual hearing loss

Hearing loss after language has developed

Which two onset groups have the best outcomes, and what is the goal for them?

• Perilingual and postlingual

• Goal: bring speech into the audible range

Which infections that cause meningitis can spread to the inner ear, and with what result?

• Pneumococcal bacteria and enterovirus

• Hearing loss and balance issues

• Bacterial meningitis causes significant hearing loss

How can bodily infections like a common cold or fever reach the inner ear?

Through the blood

Symptoms of an infection that reaches the inner ear

• Hearing loss

• Tinnitus

• Vertigo or dizziness

Labyrinthitis: what does -itis mean, and what usually causes it?

• -itis: infection (inflammation)

• Caused by a previous viral infection

Labyrinthitis: list the symptoms

• History or complaint of viral or bacterial infection (common cold or fever)

• Sudden hearing loss, usually unilateral

• Tinnitus

• Sudden vertigo (spinning) lasting 1-4 days; dizziness can last several months

Define temporary threshold shift (TTS)

• The first effect of noise exposure

• Hair cells bend over from excessive noise and take time to stand back up

Define permanent threshold shift (PTS)

Outer hair cells are dead and don't stand back up

Temporary hearing loss from noise: examples, how long it lasts, recovery time

• Gun shot, firecracker burst, concerts

• Lasts a couple of hours to a couple of days

• Hearing becomes normal after 16 to 48 hours

What exposure requires a hearing conservation program, and how does louder sound change it?

• An 8-hour work day at 90 dB

• Every 5 dB more means reduced allowed time

About how loud are concerts, and how long can you stay before a TTS?

• About 115 dB

• No more than about 7 minutes

At what level does immediate hearing damage occur?

140-150 dB

WHO: what share of 12-35 year olds are exposed to unsafe sound levels, and from what?

• 50%

• Levels of 70 dB SPL and above

• Personal audio devices and loud music (highest recreational)

WHO: what share are exposed to potentially damaging sound at environmental venues?

40%

Which occupation has the highest occupational noise-induced hearing loss?

Dentists

How has the attributed source of noise-induced hearing loss changed?

• Earlier: mostly occupational noise

• Recently: both occupational and recreational noise

What is music induced hearing loss (MIHL), and how can it be limited?

• New terminology for a societal problem

• No dissipation of sound with headphones

• Listen to music around 70 dB

List the effects of loud sounds on the cochlea

• Stereocilia damage

• Damage to outer hair cells

• Damage to inner hair cells

• Damage to the auditory nerve

Which part of the cochlea does noise affect first, and what loss results?

• The basal part

• High frequency hearing loss

What does a noise-induced hearing loss audiogram typically show?

A notch (dip) around 4000 Hz, with better hearing again at 8000 Hz

NIHL/MIHL: list the symptoms

• Hearing loss, especially in high frequencies

• Tinnitus (very common)

• Reduced tolerance to loud sounds

• Difficulty understanding speech, even without hearing loss

• Increased listening fatigue and poor working memory in older adults

Can NIHL/MIHL be permanent, and can it be prevented?

• It can cause permanent hearing loss

• It is a modifiable cause: 100% preventable

List the measures that avoid noise-induced hearing loss

• Avoid exposure to loud sound levels

• Avoid frequent or prolonged exposure

• Take breaks from earphones or personal audio devices

• Avoid earphones in background noise, or use noise cancelling headphones

Why use noise cancelling headphones in background noise?

Otherwise you'll turn the volume up

What does OSHA require for noise exposure?

Hearing protection, worn correctly

What is presbycusis, and can it be prevented?

• Hearing loss due to aging

• No way to prevent it

How does aging change the inner ear?

Anatomical changes: modified structures, function, and degeneration

What share of people aged 65-74 are expected to have hearing loss?

25 to 30% (1 in every 4)

What share of people over 75 are expected to have hearing loss?

• 40 to 50% (1 in every 2)

• Grows with each decade

Why is presbycusis sometimes hard to separate from other causes?

• You can't tell noise exposure contribution from aging contribution on the audiogram

• Factors: built-in genetic changes and environmental

List the five types of presbycusis and the site of each

• Sensory: organ of Corti

• Neural: auditory nerves

• Metabolic: stria vascularis

• Mechanical: basilar membrane properties

• Central: brain

Which presbycusis type involves changes in the organ of Corti?

Sensory

Which presbycusis type involves degeneration of the auditory nerves?

Neural

Which presbycusis type involves degeneration of the stria vascularis?

Metabolic

Which presbycusis type involves changes in basilar membrane properties?

Mechanical

Which presbycusis type involves the brain and may not show on an audiogram?

Central

Why is it difficult to tell the presbycusis types apart?

• It all looks sensorineural

• Testing can only determine sensory or neural

• More than one type of change can cause the loss at any point

Sensory presbycusis: audiogram, onset, and word recognition

• Steeply sloping configuration

• Starts in middle age

• Sensory hair cell destruction; first turn affected (high frequency SNHL)

• Word recognition preserved

Neural presbycusis: what happens and how the audiogram looks

• Hair cells preserved, but first order neurons deteriorate

• Downward sloping, but flatter than the sensory type

• Affects the entire cochlea, but mostly the basal turn

Neural presbycusis: how is word recognition affected?

• Poorer than expected from the audiogram

• Phonemic regression

Define phonemic regression

• Word recognition (speech understanding) is poorer than expected from the audiogram

• The person can hear speech but can't understand it: "I can hear you, but I can't understand you"

• Seen in neural presbycusis

Metabolic presbycusis: audiogram, word recognition, and lesion

• Flat configuration

• Word recognition preserved (little effect in some cases)

• Strial atrophy occurs as an isolated lesion

• Need at least 30% strial loss to show up on the audiogram

Mechanical presbycusis: audiogram and what changes

• Gradual downward sloping configuration

• No real signs in the cochlea except a stiffer basilar membrane

• Reduced mechanical-electrical transduction

Which two presbycusis types preserve word recognition?

• Sensory

• Metabolic

What is the number one complaint in presbycusis?

• Difficulty hearing children and women

• Difficulty hearing in background noise (restaurants, church, family gatherings, TV)

Presbycusis: typical hearing loss pattern

• High frequency hearing loss

• Usually symmetrical (same in both ears)

Presbycusis: list the main symptoms

• Reduced speech understanding

• Difficulty understanding speech in noise (can hear, but poor word recognition)

• Reduced tolerance to loud sounds or recruitment

• Tinnitus

Define recruitment

• Abnormal growth of loudness: loudness stays stable, then spikes to abnormally loud

• A common side effect of sensorineural hearing loss (cochlear damage)

Define hyperacusis

• All loud sounds are perceived as too loud

• Loudness growth is normal

• Not associated with cochlear damage

List the consequences of untreated hearing loss

• Poor communication, progressive in nature (don't use it, lose it)

• Social isolation, feeling of exclusion

• Cognitive impairment (dementia, Alzheimer's more likely)

• Increased mental health issues (anxiety, depression)

Where does untreated hearing loss rank among causes of cognitive decline?

• One of the top 4 factors

• The most preventable

How does treating hearing loss affect cognitive decline?

Treated hearing loss means slower cognitive decline

How much more likely are people with hearing loss to fall?

30% more likely (balance issues)

On average, how many years do people wait to get hearing aids?

7 years

What share of people who need hearing aids get them, and why not more?

• About 25% (now about 27%)

• Barriers: cost, stigma, insecurity, fear of technology

What happens if someone gets a hearing aid in only one ear but needs two?

The unaided ear's word recognition declines by about 40%

Meniere's: prevalence and incidence

• Prevalence: 15,000 to 40,000 per 100,000

• Incidence: about 45,500 new cases each year

At what age is Meniere's first seen?

Between 35 and 45 years

What causes Meniere's?

Too much endolymph in the inner ear (membranous labyrinth)

Meniere's: how long does the first episode last, and how do episodes occur?

• 2 to 6 days, usually the worst

• Episodic, randomly, with no rhyme or reason

How is Meniere's diagnosed?

• Can only be confirmed by a transtympanic test

• Typically diagnosed by symptoms

Define cochlear Meniere's

Auditory symptoms present, but no vestibular symptoms

Define vestibular Meniere's

Vestibular symptoms present, but no auditory symptoms

When is the term Meniere's syndrome used?

When there is a known cause for the symptoms

When is the term Meniere's disease used?

When there is no clear etiology (unknown after all possibilities are eliminated)

Meniere's: list the expected presenting complaints

• Aural fullness

• Roaring tinnitus

• Fluctuating hearing loss

• Vertigo

• Hyperacusis

What is usually the first symptom of Meniere's?

Aural fullness (different from hearing loss)

Define tinnitus, and describe the roaring type

• Any sound in the ear that doesn't come from an external source

• Roaring: sounds like the ocean or a freight train

What are the four classic signs of Meniere's?

• Aural fullness

• Roaring tinnitus

• Fluctuating hearing loss

• Vertigo

Meniere's syndrome: list the expected past medical history causes

• Head trauma

• Ear surgery

• Viral infections such as mumps or measles

• Cogan's syndrome

• Syphilis (late stage)

Meniere's: treatment and referrals

• Remove sodium from the diet (salt-free)

• Transtympanic steroid injections

• Prescription strength vertigo medications

• Refer to ENT and to an audiologist

Meniere's audiogram: early stages

• Unilateral fluctuating moderate sensorineural hearing loss at 250-1000 Hz

• Falling to mild to moderate at 4000 Hz

Meniere's audiogram: later stages

• Unilateral flat moderate to moderately severe sensorineural loss

• Eventually becomes permanent; episodes mean hearing aids must be changed