Disorders of the Ear Flashcards Preview

MODHIII - Unit 3 > Disorders of the Ear > Flashcards

Flashcards in Disorders of the Ear Deck (37)
1

Example of conductive hearing loss

otosclerosis

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Otosclerosis: disease process

- osteodystrophy of endochondral bone leading to bone remodeling
- effects otic capsule bone (temporal bone), where stapes footplate articulates w/ the vestibule
- slowly progressive so hearing loss occurs gradually

3

Otosclerosis: inheritance

- autosomal dominant, 40% penetrance
- can also affect inner ear function

4

Otosclerosis: treatment

- hearing aids
- surgical replacement (stapedectomy, most common): >90% improve, 1% with severe hearing loss
- observation

5

Sensorineural hearing loss: disease process

- occurs when there is damage to inner ear

6

Sensorineural hearing loss: 3 categories

- sensory: damage to hair cells
- neural: damage or loss of auditory neurons
- strial: damage or degeneration of stria vascularis
**most patients have components of each**

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Sensorineural hearing loss: examples

- DFNB1
- noise induced hearing loss
- auditory neuropathy

8

DFNB1: disease process

- autosomal recessive SNHL due to mutation in GJB2 that encodes connexin 26
- accounts for 50% of congenital, autosomal recessive nonsyndromic hearing loss

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DFNB1 treatment

- cochlear implantation effective in most patients

10

Noise induced hearing loss: prevelance

- most common cause of preventable SNHL
- common diagnosis for workman's compensation

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Noise induced hearing loss: cause

- most frequently occurs from exposure through years >90dB
- can result from single exposure to very loud noise

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Noise induced hearing loss: disease process

- initial damage occurs at post-synaptic structures and afferent fibers innervating inner hair cells
- later there is loss of hair cells and auditory neurons and fibers

13

Auditory neuropathy: clinical presentation

- absent ABR with intact otoacoustic emissions

14

Auditory neuropathy: cause and treatment

- DFNB9: mutation in otoferlin
- treatment: excellent results with cochlear implantation

15

Auditory neuropathy: otoferlin (DFNB9)

- otoferlin is a calcium sensitive protein involved in synaptic vesicle release from hair cells
- otoferlin mutation hair cells are present and function except fail to release glutamate to activate auditory nerve

16

Hearing assessment: subjective vs. objective

- subjective: audiogram
- objective: auditory brainstem response(ABR), otoacoustic emissions(OAE)

17

Auditory brainstem response

- test integrity of auditory system through the brainstem
- NOT used as a screening test
- used when newborn fails OAE

18

Otoacoustic emissions

- low intensity sounds recorded from ear canal response to stimuli
- reflect OUTER HAIR CELL function
- most common test for newborn hearing

19

How can you still pass OAE and be deaf

- auditory nerve dysfunction

20

Chochlear implants

- electrodes placed in chochlea that directly stimulate the auditory nerve, bypassing the non functioning hair cells
- patients usually get about 8 channels

21

Hybrid hearing process

- shorter and thinner chochlear electrodes preserve residual low frequency hearing
- patients use both acoustic and electrical stimulation

22

Vestibular ocular reflex

- allows for gaze stabilization during head motion
-hair cells of utricle, saccule and semicircular canals are activated or inhibited and lead to movement of eyes in opposite plane/direction so images remain stable on the retina

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Nystagmus

- acute abnormal activation or inhibition of vestibular nerve that drive eye movements in absence of head motion

24

Vertigo

- illusion that the external environment is in motion
- due to nystagmus

25

Videonystagmogram (VNG) & Electronystagmogram (ENG)

- use caloric stimulation to create currents in endolymph that drive VOR

26

Caloric stimulation

- irrigation of external auditory canal with cold or warm water/air

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ENG/VNG caloric testing

- Cold water: inhibitory current like a head turn to opposite side; slow phase towards irrigated ear and fast (nystagmus) towards opposite ear
- Warm water: excitatory current like a head turn to same side; slow phase away from irrigated ear and fast (nystagmus) towards irrigated ear

28

Meniere's disease signs

1. fluctuating, low frequency SNHL
2. recurrent vertigo
3. tinnitus in affected ear
4. aural fullness or pressure

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Does meniere's disease effect one ear or both

- only ONE ear

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Cause of meniere's disease

- unknown
- affected ear always has endolymphatic hydrops (swelling of endolymphatic fluid compartment)
***not everyone with endolymphatic hydrops has meniere's disease***

31

Treatment of meniere's disease

- low salt diet and diuretic: common and effective treatment
- steroids
- surgery for intractable cases (

32

Surgical management of intractable meniere's disease

- endolymphatic shunt (most common)
- labyrinthectomy
- vestibular nerve section

33

Endolymphatic shunt

- silastic shunt into endolymphatic sac
- controversial: 70% success rate
- non destructive outpatient with short recovery

34

Labyrinthectomy

- destruction of vestibular organs, requires compensation period (3-6weeks)
- surgical: 95% success rate, total hearing loss-best for those with poor hearing
- chemical (gentamicin): 70% success rate, 20% hearing loss, long term compensation sometimes not complete

35

Gentamicin

- affects vestibular cells first and then chochlear cells
- must assess vestibular function not hearing because by the time it effects hearing there will already be perminent hearing loss

36

Vestibular nerve section

- most complex procedure, required craniotomy
- 90-95% success rate, 5% hearing loss
- best for young patients with good hearing
- 3-6 weeks recovery period

37

Conductive hearing loss

- problem with ear canal, tympanic membrane and or ossicles
- does not effect ability to discriminate sounds or understand words