Quiz 2 (Inner Ear) Flashcards
bring about transduction mechanism and allows nerves to integrate the signal
ihc
which ion channels are disrupted in connexins
potassium
what is inner ear homeostasis
chemical equilibrium of the IE fluids for proper functions
inner ear functions include
hair cell fxn
regulation of extracellular endo and perilymph
conduction of nerve impulses
major ions
sodium
potassium
chloride
calcium
Ion movement is controlled by genes, channels, and water
true
help maximize sensitivity of hair cells
metabolic support behind hearing
endo and perilymph
describe the inner ear endocochlear potential
intracellular potential is -80mv and high potassium in the endolymph creates + 80mV EP so this creates a 160mV differential potential
what is the differential potential needed for
to cause hair cell shearing and electrical signaling
EP in the vestib system is only
5-10mV
EP is higher where
in cochlea than vestibular system
at basilar end than apical
what happens after shearing of stereocilia
stereocilia are displaced by motion of IHC or shearing of OHC
both rush potassium into the cell
what happens when peri and endo fluids are the same
causes reduced transduction resulting in Meniere’s disease (mixing of both)
Stria vascularis generates
potassium and has connexin gap junctions that facilitate potassium transport
The junctions are tight and contribute to the endocochlear potential because
they limit intracellular leakage of ions
gap junction
for potassium
tight juction
for blood/vascular cells
why is stria susceptible to many genetic disorders
becuase it is controlled by connexin gap junctions that faciliate K+ transport
cochlear disorders that disrupt stria, channels, transporters, gap or tigh junctions reduce
EP and result in HL
A gap junction or nexus is a specialized intercellular connection that
directly connects two cells allowing molecules and ions to pass freely between the two
what are aquaporins
proteins that regulate the flow of water
play a role in water homeostasis
blood-brain barriers and blood-labyrinthine barrier
an cause viral infections if damaged
Increased K+ transport in the endolymph or increased endolymph production
endolymphatic hydrops (too much endolymph - Meneire’s - progressive fluctuating snhl)
Decreased K+ transport in the endolymph or decreased endolymph production
endolymphatic xerosis (connexin, JLNS - permanent snhl)
causes the most genetic HL in humans
endolymphatic xerosis
abnormal connexin gap junctions, over 50% nonsyndromic HL
connexin 26
protein that makes K+ channels, responsible for reduced endolymph in HL with JLNS syndrome
KCNE1 & KCNQ1
which condition are KCNE1 KCNQ1?
jlns
DFNA
Deafness, Nonsyndromic, Autosomal Dominant
DFNB
Deafness, Nonsyndromic,Neurosensory, Autosomal Recessive
DFNX
Nonsyndromic deafness, X-linked
temporary disorders of ion homeostasis
sudden hl onset
diuretic ototoxicity
autoimmune labyrinthitis
Meniere’s disease
what indicates HL as homeostatic issue and not hair cells
these disorders manifest temporary hearing loss and recovery indicates that the damage is not to the hair cells but to the ion homeostatic process
symptoms of cochlear disorders
constant or fluctuating HL
almost always SNHL (can have mixed)
speech perception issues
loudness recruitment
aural fullness
tinnitus
conditions paired with psychological issues
hyperacusis
hurts when sound is too loud
misophonia
intense emotional feeling towards specific sounds
noise sensitivity
reaction to discomforting sounds
doesn’t have to be loud
phonophobia
fear of sound
makes tinnitus worse
common causes of SNHL
presbycusis
exposure to toxic levels of noise (noise induced HL
what causes inner ear infections
mostly viruses
some bacterial (meningitis)
two kinds of viruses known
RNA virus (covid & flu)
DNA
what is RNA virus
contain rna in their genome, mutate quickly due to lack of proofreading making it difficult to treat
what is dna virus
these contain dna in their genome and are more stable
smallpox, herpes, chickenpox
what is an example of rna virus
rubella & paramyxovirus
what is rubella virus
rna virus
responsible for german measles, effects A.S. if contracted by mom in first part of 2nd trimester when it is developing
rubella virus leads to
congenital HL, cataracts, cardiovascular cataracts, maybe intellectual disability
what is paramyxovirus
rna virus
responsible for mumps & causes male infertility
paramyxovirus leads to
parotid gland inflammation causes acquired unilateral SNHL
example of DNA virus
cytomegalovirus CMV
what is CMV
herpes family, most common viral disease in humans
50-80% US people have the antibodies by their 40’s
Decreased life expectancy, large liver and spleen, a “blueberry muffin” rash, and decreased immunity to fight off other diseases
Has the MOST GENES of any virus
most common newborn virus
CMV
if mom has CMV, what should they do
not breastfeed for first 3 weeks to avoidpassing it on
audio findings of cmv
progressive profound permanent SNHL by 3-5 yrs
kids are ci candidates
why are cmv newborns hearing unetected
it can be late onset or we are not screening for it
problems cmv causes
neurological deficits, blindness, ID, and cardiovascular problems
how is cmv diagnosied
GOLD STANDARD IS URINE POLYMERASE CHAIN DNA
can also do histological exam of inclusion bodies in saliva and lungs
CT to show intracranial calcification
are inclusion bodies specifc to cmv
NO shown in many viruses
Viral infections are destructive and causes
Damage to the basal turn of the cochlea (high freq SNHL)
Hair cell damage
Stria vascularis atrophy
Tectorial membrane rolls up
Reissner’s membrane collapses
high frequencies and pure tones cause more damage than low frequencies and WBN
true
what is meningitis
inflammation of the meninges of the brain and spinal cordwha
etiology of meningitis
virus & bacteria
primary meningitis
originates in meninges
secondary meningitis
originates outside of the meninges and travels to them (ex: cholesteatoma or OME → mastoiditis)
signs and symptoms of meningitis
Initially: high fever, neck stiffness, malaise, nausea, vomiting
Untreated: blindness, paralysis, hearing loss/deafness (causes acquired SNHL), and vertigo/off balance
treatment for meningitis
antibiotics (do a spinal tap to see which one to give), mastoidectomy (if related to the ME), amplification/CI (ensure cochlea isn’t overgrown with bone, and that there is enough space to put a CI)
what is a perilymphatic fistula
ME and IE have a connection to each other when normally they are self contained at either or both oval and round windows
etiologies of perilym fistula
idiopathic
feeling ear “pop” after heavy lifting
randomly found during Meniere’s surgery or stapedectomy
symptoms of perilym fistula
vertigo without HL
HL without vertigo
symptoms that cannot be determined from Meniere’s (SNHL, vertigo, tinnitus, aural fullness)
not episodic vertigo but disequilibrium with miscellaneous symptoms
how to determine perilym fistula
presentation of complex symptoms
case history, symptoms they present with and can have different presentations of symptoms
high index of clinical suspicion
dix hallpike to see nystagmus or vertigo
treatment of fistula
no heavy lifting
me exploration
surgery to seal leak
what can happen after repair of fistula
preserve hearing that is left
resolve balance issues
improve tinnitus
what is noise induced hearing loss (NIHL)
Hearing loss as a result of harmful noise exposure (dose/level and duration/time dependent)
dose
leveld
duration
time
has most weight for human hearing
.5-8kHz
noise notch bw 3-6000 Hz (peak bw 4 & 6kHz)
due to cochlea geometry & blood supply
NIHL
what hearing sensitivity change will we see with NIHL
max damage is ½ an octave above stimulating frequency (ex: stimulating at 1 kHz but HL at 1.5 kHz)
temporary threshold shift
reversible shift that can resolve 15 mins after exposure or persists up to 14 hours
produced by initial noise exposure
dull or muffled sound quality (at end of work shift or loud concert)
even if TTS shift comes back to baseline, can result in hidden hearing loss where there is no change in hearing but there is residual issues
permenant threshold shift (PTS)
persistent change in sensitivity, persists after approx. 14 hrs
noise is bad and long enough that it doesn’t go back to baseline
if at 125 dB it is permanent
Both accompanied by tinnitus (can be a useful warning if you get it after a temporary shift)
true
Initial noise exposure produces TTS, but a daily dose of noise exposure that DOESN’T cause TTS WILL NOT cause PTS
true
effects on me and noise
rare
™ perf after blast =
possible concussion
, >/= 165 dB SPL can cause
™ perf,
> /= 190 dB SPL can cause
ossicular chain injury
inner ear and noise
can result in tinnitus and oHC damage
stereocilia first lose stiffness (TTS) and after repeated damage becomes permanent (PTS)
more intense & prolonged loud sounds =
greater degree of hair cell loss
can noise cause NIHL vestib issues
doubtful BUT ACOUSTIC TRAUMA CAN
COCHLEA MORE SUSCEPTIBLE TO NOISE LOSS, ME depending on loudness level
TRUE
how to diagnose NIHL
clinical hx & audio data showing SNHL
medical exam to rule out other causes of HL
audio configuration
usually symmetrical but asymmetries >/= 15 dB HL not uncommon(usually in HF - 3 to 6 kHz, with firearm use)
profound SNHL rare, LF thresholds better than 40 dB HL, HF thresholds rarely better than 75 dB HL
presbycusis can flatten noise notch
notch flattens when noise induced meets presbycusis
true
management of NIHL
no effective treatment
PREVENTION IS BEST MANAGEMENT
use of appropriate amplification w/ permanent HL
use of antioxidants & other chemicals that protect against NIHL (being investigated)
what is acoustic trauma
form of NIHL that is a sudden, permanent HL as a result of a single event (NO TTS)
Caused by impulse noise of 165-190 dB SPL that causes direct mechanical damage to the cochlea (can also rupture the eardrum)
Impulse noise over 140dB SPL can also cause PTS immediately
true
sound intensity bw 165 to 190 dB SPL
ruptures or produces ™ hemorrhage
disrupt/fracture ossicular chain
otoscopy on acoustic trauma
tm perf or hemorrhage
audio results for acoustic trauma
similar to NIHL
noise notch at 3 & 6 kHz
HF sloping configuration
flat configuration (more common)
mixed HL = if ossicular disarticulation has occurred
tymps of acoustic trauma
type Ad if ossicular disarticulation
which parameter is abnormal in type Ad?
static admittance
perf tymp?
type b with high ECV
type b but not high volume?
peak pressure is not measured
admittance is not measured
just volume is measured
art in acoustic trauma
absent if ossicular disruption
HL may improve over 4-6 mo period if from acoustic trauma
true
surgery could be used to repair ™ and ossicles if they are damaged in acoustic trauma
true
why can we not replicate hair cells?
they are in G0 phase that stops the cell cycle
when you take it out it messes with the cycle and causes tumors throughout the body
*have to find a way to counterbalance this before regenerating hair cells
what are blast injuries
type of acoustic trauma
caused by indirect impact from pressure wave created from an explosion
blast injuries are more dangerous why
when bomb goes off, pressure wave causes damage
so much heat and pressure when it goes off
damage as result of blast injury
™ perf, ossicular disarticulation, tinnitus, otalgia, HL and/or vertigo
why is otologic usually initially missed
this is because high priority is for life threatening injuries
