570 Inner Ear Pathologies

Temporal bone trauma

causes:

• blunt trauma

  • motor vehicle accidents (MVA) - leading cause

  • recreational vehicle accidents

  • falls

  • assaults

• penetrating injuries (high mortality rate)

  • gunshot injuries

  • stabbing

• AR:

  • audiologic eval for monitoring recovery

    • initial eval once stable

    • otoscopy, comprehensive audio and tymp

    • type and severity of HL depends on fracture pattern

  • facial nerve testing (acoustic reflex), vestibular assessment, follow up audio

  • hemotympanum related CHL resolves 1 mo, ABG suggests ossicular injury, type Ad tymp

  • labyrinthine concussion: SNHL and/or vertigo

longitudinal temporal bone fracture

70-80%

• when blunt forceis applied to lateral portion of skull

• parallel to long axiz of petrous bone

• often involves external canal and ME

• CHL, TM perf, ossicular disruption, facial nerve injury (20%)

through EAC

• bloody otorrhea

• Torn TM

• bony canal step off

through mastoid air cells

• intact TM

• hemotympanum (blood in ME)

• battle’s sign

transverse temporal bone fracture

20%

• when force applied to frontal/occipital

• perpendicular/transverse to petrous ridge

• involves otic capsule, cochlea/vestibule, internal auditory canal

• SNHL, vertigo, facial paralysis (50%) possible CSF leak

• through occipital bone, extends to foramen magnum

• fractured otic capsule

  • complete loss of inner ear function - profound SNHL w/ vertigo

  • CN VII injury (50%)

Presbycusis cochlear changes

• degeneration of Organ of Corti

  • sensory cell degeneration

  • loss of supporting cells

  • loss begins at base, OHC first, more severe degeneration in outer row of OHC - loss of high freq

  • degeneration of OHC associated with noise trauma

• degeneration of spiral ganglion cells

  • 90-95% are type I and connect to inner hair cells (myelinated)

  • 5-10% are type II and connect to OHC

  • loss is greatest near base

  • decreased number in cochlear nerve

  • can loose nerve fibers w/o hair cells - invisible on audio

  • loss of ganglion cells related to pure-tone hearing loss

  • speech rec worse with sig. ganglion loss

Schuknechts subtypes of presbycusis

• sensory presbycusis

  • abrupt (steep) high freq loss; WRS consistent with dregree of loss

  • OHC loss associated with noise and toxins

• neural presbycusis

  • shrinkage and diffuse loss of ganglion cells

  • WRS disproportionately poor relative to pure tone thresholds

• Strial Presbycusis

  • flat audiogram

  • WRS typically preserved

  • Metabolic tissue (stria vascularis and lateral wall of cochlea)

  • reduced endcochlear potential

  • atrophy of stria vascularis

• cochlear conductive/mechanical presbycusis

  • stiffening of basilar membrane (decrease in elasticity and thickening) and organ of Corti

  • gradually descending, straight line audio

  • other varieties ruled out/more theoretical (extreme form of metabolic presbycusis)

• mixed presbycusis - 2 or more of the 4 classic

• indeterminate presbycusis (25% of cases)

  • flat or mildly descending without a consistent or distinct pathological correlate

presbycusis audiology findings

• comprehensive audio

  • generally reveals a sloping, bilateral SNHL that gradually progresses over time

  • significant variability - degree of HL correlated with age

  • significant variability in WRS - central auditory decline

• recruitment (reduced dynamic range)

• other common findings

  • reduced or absent DPOAEs

  • acoustic reflexes at near-normal dB HL (reduced sensation level)

  • poorer speech in noise performance than audio predicts

presbycusis mangagement

• avoid/reduce exposure to noise

• HAs

• ALDs

• Aural rehab and support groups

• CIs

• OTC hearing aids

• why it matter: hearing loss is 7% of modifiable dementia risk - intervention did not slow cognitive decline but helps higher risk adults

NIHL acoustic trauma

• acute noise exposure

• due to one-time brief exposure

• can cause permanent SNHL

• blast trauma is a significant concern in military and veteran (VA) audiology

• often accompanied by head trauma

• can tear inner ear membranes and disruption of cell walls (mix perilymph and endolymph)

• my be vascular congestion in TM or perf a few days after onset

• ossicular damage is possible

AR:

• audio thresholds mild - severe

• may be loss of speech discrim.

• pt. may have spontaneous nystagmus and/or reduced caloric response

• rare - complete loss (rule out fistula, early surgical intervention may recover some)

• after acute NIHL - hearing will improve for a few days/weeks, complete recovery is rare

• 
  

NIHL chronic exposure

• longer term exposure - often lower levels

• occupational noise exposure typically chronic

  • Osha: unprotected exposure to steady-state noise 8 hr per day at 90dBA; hearing conservation program in place if a time weighted average noise level of 85 dBA or higher over 8 hr shift; no unprotected exposure above 115 permitted

NIHL tts

• reversible loss following noise exposure

• OSHA require >= 14 Hr w/o workplace noise (or w/ HP) before baseline audio

• fully reversible TTS still destroyed >50% of hear cell-nerve synapses

• recovered audio does not = no damage

PTS

• if exposure continues/more intense, TTS becomes PTS

• ending exposure stops progression of threshold loss

NIHL pathophysiology

• floppy stereocilia

• loss of stereocilia on OHC

• loss of OHC

• loss of IHC

• sections of basilar membrane w/ no organ of corti

• impact 4k first - why notch?

  • ear canal resonance (2.5-3 kHz) boosts energy reaching cochlea

  • max damange occurs ½ octave above exposure frequency

  • acoustic reflexes attenuate low frequencies

  • continued exposure causes notch to deepen and widen (2-3 and 6kHz) - 8k normally spared

NIHL audiogram

• bilateral symmetric, worse in high freq, SNHL

  • exception: shooters - worse in ear opposite shooting should

• for relatively broad band noise exposures, 3-6kHz affected

• band limited - loss is ½ - 1 octave above frequency of exposure and 3-6kHz range

• progression to profound loss is rare

• maximum loss seen after 10-15 years exposure

• diagnose based on history and audio pattern

• unexplained asymmetry needs retrocochlear workup

• 4 kHz notch

NIHL counseling

• NIHL

  • noise may be hazardous if: appreciably louder than conventional levels; difficult to carry conversation at 3 feet, sufficient to cause tinnitus, sufficient to cause feeling of muffled hearing

• ear protection

  • generally attenuates high frequencies more than low frequencies

  • labeled NRR overstates real-world protection, mainly because of fit

  • cotton in ears provides 5dB attenuation

• young adults

  • snow mobiles

  • personal listening devices

  • fitness classes

  • radio-controlled model airplanes

  • cap guns

  • band

• preventing

  • know which sounds can cause damage

  • wear earplugs or other HPD

  • be alert to hazardous noise in environment

  • protect kids who cant themselves

  • baseline hearing test

  • promote public awareness

OSHA standard

5 dBA exchange rate - when noise is increased by 5 dBA amount of time exposed is cut in half (8 hr = 90dBA, 4 hr = 95dBA …)

• impulse/impact noise should not exceed 140 dB peak SPL

• NIOSH recommended limit: 85 dBA for 8 h w/ 3 dB exchange rate

ototoxicity

• subclinical or profound deafness and impaired balance

• permanent or temporary (usually perm. an reversible)

• bilateral SNHL and tinnitus - OHC and high freq affected first and stronger

• vestibular dysfunction

• >= 20 dB decrease at one freq

• >= 10 db decrease at two adjacent freq

  • loss of response at three consecutive freq

• AR: educate physicians/patient/family abt need for monitoring

Common ototoxic drugs

• aminoglycoside antibiotics - mycins

  • broad spectrum antibiotics

  • given in NICU - genetic susceptibility

  • wide range of bacterial infections

• chemotherapeutic agents

  • cisplatin - permanent HL in 40-80% of treated patients (carboplatin)

• loop diuretics (1-6%)

  • furosemide (lasix)

  • ethacrynic acidd

  • widely used for pt with heart failure, fluid retention problems, pneumonia, kidney problems

• non-steroidal anti-inflammatory drugs (NSAID)

  • salicylates (asprin) or ibuprofen

• quinine (treat malaria)

• topical agent (cortisporin)

  • applied to EAC for otitis externa - toxic if TM perf

  • if TM non-intact, not toxic drops preferred

ototoxic risk factors

• renal dysfunction

  • clearance of aminoglycoside antibiotics requires kidney filtration

  • impaired renal fn can result in higher drug levels and longer exposures

• liver dysfunction

  • some ototoxic factors are cleared in liver

  • impaired liver fn can cause greater exposure

• previous tx with ototoxic drugs

  • increase susceptibility

  • cisplatin retained in cochlea for months to years

• pharmacologic factors

  • other drugs precipitate effects of ototoxic medication

  • use of multiple ototoxic drugs

ototoxic monitoring

• baseline audio thresholds and OAE before starting med

• high freq. audio

  • more sensitive early markers

  • test above 8K up to 16-20k

  • rationale is to identify hearing loss before reaches speech range

  • difficult due to freq. response of transducer used

• OAE

  • do not require subject participation

  • sensitive to high freq loss

  • many ototoxic drugs affect OHC first

• DPOAEs may detect ototoxic change earlier than TEOAEs

SSNHL

• decrease in hearing of >= 30 dB vs prior audio or contra ear

• occurs over 72 hours or less

• affecting at least 3 consecutive freq

• symptoms:

  • varies in degree

  • selective LF or HF HL

  • distortions in speech perception

  • tinnitus in up to 70% of cases

  • dizziness/vertigo in 30-60% of cases

  • usually unilateral

  • bilateral SSNHL rare- prompt search for systemic cause

SSNHL pathophysiology

• idiopathic >90%

• proposed mechanism

  • labyrinthine viral infection

  • labyrinthine vascular compromise

  • labyrinthine membrane ruptures

  • immune mediated IE disease

  • abnormal cellular stress response in cochlea

• identifiable causes <10%

  • autoimmune: AIED, lupus

  • neurologic: MS, migraine

  • neoplastic: vestibular schwannoma → MRI for every patient

  • infectious: otosyphilis (treatable)

  • 
    

SSNHL viral pathophysiology

• viral infection is circumstantial

  • lesions resemble viral cochleitis but antivirals do not improve recovery

• histologic studies

  • loss of hair cells

  • loss of supporting cells

  • atrophy of tectorial membrane and stria vascularis

  • loss of neurons

• damage pattern consistent with

  • herpes virus family (zoster)

  • secondary to measles, mumps

SSNHL vascular pathophysiology

• due to

  • reduced blood flow

  • vasospasm (lengthy constricting, narrowing/tightening in artery)

  • thrombosis (local clotting of blood)

  • embolus (clot carried in blood, lodged in vessel

• cardiovascular risk factors

  • smoking, alcohol, inherited clotting-risk variants

  • fibrinogen: not factor, but high levels predict poorer recovery

• 1.4 times higher stroke risk after SSNHL

• temporal bones rarely show vascular damage

SSNHL tx

• salvage hearing by using steroids

  • systemically (oral) - option within 2 weeks of onset

  • intratympanic perfusion

    • clinicians offer patients intratympanic steroid salvage therapy where there is incomplete recovery from 2-6 weeks after onset

• hyperbaric oxygen + steroids: option within 2 weeks (initial) or 1 month ( salvage)

• not routinely recommended: antivirals, thrombolytics, vasodilators, vasoactive drugs

• serial audiograms

• stable hearing loss shows no improvement after 3-6 months (HAs - CROS, Bi-CROS; CIs)

SSNHL prognosis

complete or partial

• spontaneous recovery in 32-65%

• usually within first 3 days post-onset and no later than 1-2 weeks post-onset

• poorer prognosis with:

  • profound hearing loss

  • delayed treatment >10 days

  • extremes of age

  • presence of hypertension

  • vertigo at onset

CROS vs BiCROS

cros - unaidable HL going to normal hearing ear

bicros - unaidable HL going to aidable hearing loss ear

AIED

• inflammatory condition of inner ear

• theory: immune system fails to distinguish body’s own cells from invaders and attacks healthy cells in inner ear mistaken for virus

• rare: <1% of all SNHL

AIED presentation

• rapid progressive (fluctuating) SNHL

  • HL can progress over weeks or months (about 3 months)

  • 80% bilateral - can start in one ear and other follows, sudden HL in one progress rapidly to other

• tinnitus

• vertigo or imbalance (50%)

  • range from subtle disequilibrium to motion intolerance, positional vertigo, true episodic vertigo

AEID tx

• goal: hearing stabilization, some cases improvement noted

• systemic steroids (manage acute hearing changes)

• steroid-sparing agents (long-term management)

• plasmapheresis - “washing” of blood

• HAs and CI may be considered if patient is unresponsive to drug therapy and HL persists

AIED vs SSNHL

time course:

• A - weeks - months

• S - <72 hours

laterality

• A - bilateral (asymmetric)

• S - unilateral

hearing

• A - progressive SNHL, may fluctuate

• S - sudden drop, any configuration

vestibular

• A - imbalance in 50%

• S - dizziness/vertigo in 30-60%

steroid response

• A - defining feature ( 58% improve)

• S - treatment option; partial recovery common