lecture 15: disorders of the inner ear, nerve, & central pathway - exam 3 Flashcards
prenatal
congenital
disorder occurs before birth
postnatal
acquired
after birth
prenatal causes
malformations
genetic –> syndromic & non-syndromic
environmental
most etiologies of prenatal hearing loss are unknown – 64%
michel / complete labyrinthine aplasia
complete failure of development of inner ear & auditory nerve –> NO COCHLEA
pretty rare
can be unilateral, bilateral, or one type on one side & another type on the other side
mondini dysplasia
incomplete development & malformation of the inner ear –> PARTIAL COCHLEA
1-1.5 turns of cochlea (should be 2.5)
more common than complete
can be unilateral, bilateral, or one type on one side & another type on the other side
treatment for complete aplasia
ASL
vibrotactile aid
auditory brainstem implant
treatment for mondini aplasia
varies depending on severity
hearing aids often sufficient
can require CI & sometimes split array CI
superior canal dehiscence
opening in the bone that covers the superior semicircular canal of the inner ear
disrupts vestibular system
- cant keep eyes straight while moving
- loud sounds cause dizziness too
SNHL
genetic causes of hearing loss
50-60% of children w hearing loss (known cause)
can be syndromic (30%) or nonsyndromic (70%)
congenital hearing loss branches
environment - 25%
genetic - 60%
other - 15%
syndromic
hearing loss associated w/ other symptoms
400 syndromes associated w/ hearing loss
non-syndromic
hearing loss not associated w/ any other symptoms
prelingual
occurs before the child has developed language
pendred syndrome
SNHL from mondini dysplasia
- SNHL typically progressive
can co-occur w/ conductive HL if additional ear malformations
goitre – neck swelling from thyroid dysfunction
autosomal recessive
waardenburg syndrome presentation
heterochromia or distinct blue eyes
white forelock of hair
prominent nasal root
SNHL
have a relative w/ waardenburg –> tends to get worse w/ each generation
waardenburg affects
formation of melanocytes
create melanin - important for inner ear function
waardenburg types
several
not all cause hearing loss but when it does it is present & birth & generally stable
most autosomal dominant
usher syndrome presentation
SNHL & retinitis pigmentosa
(night blindness, loss of peripheral vision)
vision loss can be progressive
what is the most common cause of deafblindness
usher syndrome
usher syndrome hearing loss
SNHL
profound at birth or less sever but progressive
brachio-oto-renal syndrome
preauricular pits/tags
branchial cleft cysts (neck masses)
abnormal kidney function
SNHL (& sometimes mixed)
stable
caused by EYA1 gene mutation
autosomal dominant
Connexin 26
40-50% of non-syndromic genetic HL
mutation of GJB2 gene makes connexin
cells along BM have underdeveloped gap junctions
almost always congenital - severe to profound
late onset possible - mild & progressive
SNHL
stable
autosomal recessive
happens a lot w incest
what is the most cause of genetic hearing loss
connexin 26
vestibular aqueduct
canal between inner ear & skull that carries endolymph to sac
enlarged vestibular aqueduct
when sac is too large endolymph can flow back into the cochlea & mix w/ perilymph (kills hair cells)
SNHL or mixed HL, progressive
can look conductive
can occur on its own or w/ other conditions (pendred, mondini, etc)
autosomal recessive
postnatal / environmental causes
infections
ototoxicity
noise induced hearing loss
Meniere’s disease
presbycusis
infection - meningitis
inflammation of the meninges
many causes (viral or bacterial)
can be fatal
meningitis HL
usually bilateral SNHL
can be unilateral
variable configuration & degree
ototoxicity
from antibiotics or cancer treatment
extended high freq audiometry & OAEs can monitor HL & be an early indicator of HL
significant shift in high freq threshold due to ototoxicity is
> 20 dB change at 1 freq
> 10 dB change at 2 adjacent freqs
loss of response at 3 consecutive freqs where there were previously responses
noise induced HL
caused by exposure to loud sound
high freqs, OAEs, ABR, & speech in noise perception may all be affected before HL detected on audiogram
threshold change can be temporary or permanent, never fully returns to normal
not always symmetrical
time/intensity tradeoff
semi loud sounds cause HL over a longer time of exposure
very loud sounds can cause instant hearing loss
general recommendation for safe listening
85 dB or less for 8 hours a day
3 dB exchange rate = for every increase in sound level of 3 dB, safe time cut in half
Meniere’s Disease symptoms
low freq
often fluctuating (only cases of fluctuating SNHL)
need multiple audiograms to diagnose
SNHL
usually unilateral but can be bilateral
progressive
roaring, low freq tinnitus
vertigo (can be very severe)
feeling of pressure in ears
meniere’s cause
generally unknown
thought to be over secretion or under absorption of endolymph in sac
meniere’s treatment
low sodium diet historically - doesn’t work
full labyrinthectomy used for severe cases
gives you full HL in that ear
presbycusis
HL due to aging
SNHL
sloping
bilateral
symmetrical
slow progression
what is the most common type of HL
presbycusis
vestibular schwannoma
benign tumor caused by overgrowth of Schwann cells on CN VIII
covers AN
usually unilateral except this one disease that causes them all over your body
vestibular schwannoma symptoms
tinnitus
SNHL
absent ARTs
poor speech perception despite normal thresholds (&/or rollover)
vertigo & balance problems
auditory neuropathy spectrum disorder
thought to be lesion in the synapses between IHCs & CN VIII or on CN VIII itself
difficult to diagnose, no gold standard
present OAEs w/ abnormal ABR
audiometry highly variable
comorbid, less common on its own
ANSD symptoms
hearing loss
poor speech perception
difficulty hearing in noise
not consistent w/ audiogram
ANSD treatment
controvertial
may implant
central auditory processing disorder symptoms
general difficulty processing speech or auditory scene
CAPD signs
difficulty w/ supra threshold psychoacoustic processing
including temporal & binaural integration & auditory discrimination
CAPD diagnosis
no gold standard or known cause
difficult to conclude domain specificity –> ear, brain, both?
audiograms & objective tests usually noral
testing varies but usually involves a series of psychoacoustic tasks
non organic HL
faking
usually for compensation (adults) or attention (teens)
cues for suspecting non organic HL
case history
inconsistency on hearing tests
hard to hold on to a specific loudness in your head
disagreement between speech reception thresholds & PTA
what should an AuD if suspected faking
objective tests
BC forehead test – can’t tell which ear they hear it in
children - say yes if you heard it & no if you didn’t
stenger test
can be used to detect non organic HL w/ difference of at least 20 dB HL between ears
stenger test stimulus
tones or spondees presented at same time in both ears
stenger test level
10 dB above threshold (of SRT) in better ear & 10 dB below threshold in worse ear
think they are heading tone just in their worse ear because that one is louder
if true unilateral HL - they will still respond bcs they are hearing the tone/spondees in better ear
