B7-041 Hearing Loss Flashcards by Felicia Jones

congenital abnormalities of the ear often happen in what weeks of development?

3-8

(inner ear forms first, followed by middle, then external)

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parts of external ear [3]

pinna
external acoustic meatus
external layer of tympanic membrane

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parts of the internal ear

cochlea

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the auricle is derived from which pharyngeal arch?

1st and 2nd

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the cartilage for the external ear is derived from

neural crest

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abnormal migrations of the neural crest cells during formation of the external ear can cause [3]

periauricular tags
anotia
micronotia

(anotia and micronotia can also be caused by issues with the 1st and 2nd pharyngeal arch)

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failure of apoptosis of the meatal plug around week 26 causes

lack of external auditory meatus

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the inner ear is derived from

ectoderm

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describe the formation of the inner ear during week 3

otic placode –> otic pit –> otic vesicle

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otic vesicle gives rise to

primordium of membranous labyrinth

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delaminating young neurons give rise to statoacoustic ganglion, which is a precursor to

vestibulocochlear ganglion

(derived from neural crest and ectoderm)

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the urticle (dorsal) of the membranous labyrinth forms [3]

endolymphatic duct
semicircular ducts/ampullae
macula of utricle

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the saccule (ventral) of the membranous labyrinth forms [3]

cochlear duct
ductus reunions
macula of saccule, organ of Corti

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hair cells of the […] are responsible for angular acceleration

ampullae

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hair cells of the inner ear are derived from

surface ectoderm

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hair cells of the […] are respond to gravity

macula

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hair cells of the […] are responsible for sound vibration

organ of corti

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the ossicles of the middle ear are derived from

neural crest

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the malleus and incus comes from the […] pharyngeal arch

1st

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the stapes comes from the […] pharyngeal arch

2nd

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[…] pharyngeal […] forms the external auditory meatus

1st pharyngeal cleft forms the external auditory meatus

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[…] pharyngeal […] forms the tubotympanic recess

1st pharyngeal pouch forms the tubotympanic recess

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tympanic membrane is derived from [3]

ectoderm
mesoderm
endoderm

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the ossicles are derived from […] and covered with […]

neural crest
endothelial epithelium

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inserts into the handle of the malleus and prevents damage from loud sounds

tensor tympani

inserts onto the neck of stapes and prevents damage from loud sounds

stapedius

tensor tympani is derived from [...] pharyngeal arch mesoderm

1st

stapedius is derived from [...] pharyngeal arch mesoderm

2nd`

tensor tympani is innervated by

CN V

stapedius is innervated by

CN VII

conduction causes of congenital deafness [3]

first arch syndrome abnormalities of malleus and incus congenital fixation of stapes

[...] infection during the 7th-8th week can result in deficits to the spiral organ causing congenital deafness

rubella

how is hearing measured in adults vs babies?

adults: subjective babies: objective

important aspects of adult hearing tests [2]

threshold as a function of frequency ability to discriminate speech sounds

impaired conduction of sound through the external and middle ear up to the inner ear

conductive hearing loss

caused by pathology of inner ear or 8th nerve

sensorineural hearing loss

caused by CNS damage, relatively uncommon

central hearing loss

normal route by which airborne sound reaches the cochlea

air conduction

vibrations are transmitted directly to the cochlea bypassing the middle ear

bone conduction

hearing loss seen with air conduction testing can be caused by

conductive and/or sensorineural hearing loss

hearing loss seen with bone conduction testing can be caused by

sensorineural hearing loss

examples of objective hearing tests [2]

auditory brainstem response (ABR) otoacoustic emissions

frequency specific threshold is measured using an [...] conduction audiometric test

air

a 20 dB increase is equivalent to a [...] in intensity

10x increase

common causes of conductive hearing loss that produces a moderate hearing loss of 30 dB [3]

cerumen otitis media otosclerosis

presbycusis cause loss of [...] frequency hair cells first

high

causes of sensorineural hearing loss [6]

high intensity sound presbycusis ototoxic drugs meniere's TORCH infections hereditary

ototoxic drugs

aspirin aminoglycosides (mycins) loop diuretics cisplatin

[...] hair cells are more susceptible to noise induced hearing loss

outer

OHCs are amplifiers, their loss results in

30-40 dB loss

IHCs are transducers, loss of all IHCs results in

deafness

treatment of sensorineural hearing loss

hearing aids, amplify sound

air conduction thresholds = bone conduction thresholds with a notch of hearing loss at a specific frequency

sensorineural (violinists commonly have a "notch", due to specific exposure of long period of time)

speech frequency is typically between [...] and [...] Hz

1000-4000 Hz

recorded using surface electrodes, stimulus-evoked

Auditory Brainstem Response (ABR)

measure of outer hair cell function recorded using a small microphone in ear canal

otoacoustic emissions testing

perception of a phantom sound that occurs in the absence of actual sound

tinnitus (often accompanied with cochlear hair cell loss)

tinnitus due to pulsation of a blood vessel

objective tinnitus

tinnitus due to dysfunction in the auditory system

subjective tinnitus (more common than objective)

does cutting the auditory nerve fix tinnitus?

no, it is a CNS problem cutting the nerve can cause more issues

hearing level below [...] indicates hearing loss

-20 dB

hearing loss measured with bone conduction reflects only [...] loss

sensorineural

if the hearing loss is only conductive, [...] will be normal on audiogram

bone conduction thresholds

air conduction and bone conduction thresholds the same

sensorineural loss

loss involving both sensorineural and conductive components

mixed

what kind of hearing loss?

conductive

what kind of hearing loss?

sensorineural (presbycusis)

what kind of hearing loss?

sensorineural (induced by specific frequency- violinists)

hair cell death will result in [...] hearing loss

permanent

overproduction of endolymph is a feature of

Menieres

otitis media would cause [...] hearing loss

conductive

fixation of the middle ear ossicles

otosclerosis (causes conductive hearing loss)

[...] frequency hair cells are more susceptible to damage with age

high

Meniere's causes [...] hearing loss

sensorineural

how do outer hair cells generate otoacoustic emissions?

create movement of basilar membrane ---> sound wave travels throughout cochlea

microtia results from suppressed [...] proliferation

mesenchymal

rubella virus causes abnormalities of what structure in fetal development?

spiral organ of corti (membranous labyrinth)