Exam 2 Flashcards
What are the two types of noise induced hearing loss (NIHL)
Noise induced permanent threshold shift (NIPTS) and acoustic trauma
Noise induced permanent threshold shift
Repeated exposures to SPLs lower than those that produce acoustic trauma
Long term exposure
Occupational ONIHL
Acoustic trauma
Permanent cochlear damage after one exposure to very high SPLs
Signs and symptoms- otalgia, drainage, perf, hemotympanum, vertigo, muffled hearing, tinnitus
Other effects of noise exposure (7)
Fatigue
Annoyance/irritation
Reduced processing capacity
Physical effects
Tinnitus, hyperacusis
Vestibular
Low and ultra high frequency effects
What fraction of Americans with hearing loss have noise exposure?
1/3
Risk factors for NIHL
White/hispanic older males
Education is at most high school
Smoking
Diabetes
Ear canal
Genetics
Cerumen
Frequency temperature
Response to sound
What is the most common cause of noise exposure
Occupational
What federal administration regulated occupational safest
OSHA (Occupational Safety and Health Act)
Complications in NIHL
Dehydration, heart disease, smoking, alcohol, diabetes
OSHA hearing standards
8 hours at 85 dBA
For every 5 dB increase, what happens to the time
It cuts exposure time in half ex. 4 hours at 90 dBA
Contributing factors when considering how much noise is too much noise
Duration of exposure
Level of exposure
Frequency spectrum of the noise
Distance from the source
Equal energy hypothesis
Equal amounts of sound energy will produce equal amounts of hearing impairment regardless of how the sound energy is distributed in time
Biologically this does not make sense
Temporary threshold shift (TTS)
Exposure to loud sound for a few hours
May seem like buzzy ears, muffled hearing
Thresholds decline but recover within hours or days
Can a TTS cause long term effects?
Yes, but the permanent consequences may not be apparent for many years
Metabolic exhaustion
Auditory fatigue
Physiologic processes cannot keep up
Ex. change in oxygen tension in endolymph, glycogen depletion, free radical breakdown
Could lead to cell death if unrelieved
Known that taking breaks away from noise during prolonged noise can avoid TTS
Preconditioning/otoprotection
Exposure to conditions that turn up innate protective pathways including HSP heat shock proteins and anti-oxidant enzymes
What can permanent damage due to the ear?
OHC and IHC damage
Supporting cell damage
Tectorial membrane damage
Changes in structure
Changes in ion levels in levels or outside of cells
Mixing of fluids
Ganglion cells and connections, channel regulation
Generation of potentials
Efferents
Central connections
General rules of NIHL PTS
SNHL, bilateral, initially a history of TTS
High-frequency losses rarely exceed 75 dB and low frequency losses rarely exceed 40 dB
Dose related
NIHL prevention
Information about what sounds can cause damage
Wear hearing protection
Be alert to hazardous noise in the workplace
Protect children
Baseline audiogram
Public awareness- educate, provide tools
Sensory hearing loss (according to Schuknecht)
From the cochlea
Degeneration of hair cells and supporting cells at the base of the cochlea
Atrophy of the organ of corti which then affects the auditory nerve
Abruptly sloping, high frequency loss
Starts at middle age and progresses slowly
Speech discrimination abilities should match audiogram
Neural hearing loss (according to Schuknecht)
Loss of dendrites and then cochlear neurons
High frequency, often mild HL
Poor speech discrimination scores (often worse than what would expect from audiogram)
Progresses rapidly with aging
Two types- primary (affects spiral ganglion cell directly, less common) and secondary (hair cells die, no input, nerve cells die)
Can cut half the nerve without changing thresholds
Can lose up to 90% without threshold change
Relevant to ANSD, central functions, hidden hearing loss
Can spiral ganglion cells survive a long time without hair cells?
Yes, there is evidence in hearing aid users
Summary of neural temporal bone studies
Number of ribbon synapses per IHC decreased with increasing age
Peripheral axon counts decreased linearly with age
Axon loss 3x greater than IHC degeneration
SGN count decrease linearly with age
Metabolic presbycusis (according to Schuknecht)
Flat SNHL with good preservation of speech understanding
Mechanical (cochlear conductive) presbycusis (according to Schuknecht)
Changes to cochlear mechanics due to mass/stiffness changes or atrophy of spiral ligament
Sloping hearing loss, including low frequencies
Speech understanding is generally good
Central presbycusis
Neuronal loss
Synaptic
Chemistry
Connectivity
Speech of processing
Physiology
Incidence/prevalence of presbycusis (for 65-75, 75+, 90+)
65-75- 30-35%
75+- 40-50%
90+- greater than 90%
General age related hearing loss (ARHL) clinical characteristics
Bilateral, symmetric SNHL (high frequencies most affected)
Progressive hearing loss with age
Initially word recognition scores consistent with PTA, but progressively poorer
Gradual onset
Negative history for noise
exposure
Normal otologic exam
DPOAEs decline independently of thresholds
SRT will increase with age
Tymps usually normal with some decreased compliance in age
ARHL trends for male/female
In U.S. females do better than males but there are ethnic differences
Female: 10-16kHz by 40s, 6-8kHz by 50s, speech frequencies by 60s
Male: 10-16kHz by 30s, 6-8kHz by 40s, speech frequencies by 60s
Does noise exposure accelerate aging of the auditory system?
Yes, will see effect on ABR
Physical effects of aging for the outer and middle ear (5)
Loss of tissue elasticity of pinna and ear canal
Stiffening of tympanic membrane
Degeneration of middle ear muscles
Calcification of ligaments
Ossification of ossicles
Clinical effects of aging for the outer and middle ear
Minor effects
Often normal tymps, immittance if HL allows
Women often have decreased compliance
Relation with extended high frequencies and ARHL
Lose them early
Most vulnerable part of the cochlea
Over the age of 40, may not have thresholds above 16k
What do extended high frequencies help with?
Sound localization, hearing in noise and auditory segregation
Underlying physiological effects with ARHL
Down regulation of neural activity that are important for speech processing
Loss of grey matter volume in primary auditory cortex
Resource allocation (sensory abilities affect which and how much brain regions are recruited for functions)
Efferent function changes with ARHL
Gain control
Inhibit cochlear amplifier
Role in signal detection in noise
Protective role during acoustic over-stimulation
Likely affected but lack of clinical testing
Cortical responses in older adults
Delayed response latency- stimulus audibility, not hearing loss related but rather neurophysiological changes
Presbycusis treatment and rehab
Counsel, alleviate symptoms, difficulty separating effects of aging from effects of noise exposure
Rehab options: HA, assistive devices, group rehab
All senses decline with age
Retrograde process
Lose ribbon synapses then auditory nerve fibers then spiral ganglion cells
Incidence of Menieres
0.2-2%
Common factors of Menieres
More common in women, 40s and 50s diagnosis
Associated with history of allergies, smoking, virus or respiratory infection
Pediatric Menieres
2.3% of MD are in children
1/3 of the children have a family history
Higher prevalence bilaterally
Overlaps with vestibular symptoms of vestibular migraines, BPV, SSNHL
Sign and symptoms of adult Menieres
Classic:
-HL
-tinnitus
-vertigo
-fullness
-fluctuation
Other:
-hydrops can be associated with the classic symptoms without vertigo
Symptoms can vary
Usually unilateral but about 40% of patients will become bilateral
70% of patients vertigo will resolve/burn out in 8-10 years
Differential diagnosis for Menieres
-CPA tumor
-BPPV
-Lyme disease
-neurosyphilis
-labyrinthitis
-vestibular neuritis
-perilymph fistula
-vestibular migraine
Meniere Syndrome
Very similar to Menieres disease but this is secondary to another disease like thyroid or an endolymphatic tumor
Basic definition of Menieres
Disorder of the inner ear characterized by dysfunction in the fluid balance-regulating system
Characteristics of definite Menieres (according to guidelines)
-two or more spontaneous attacks of vertigo, each lasting 20 minutes to 12 hours
-audiometrically documented low to midfrequency SNHL in the affected ear on at least 1 occasion before, during or after 1 of the episodes of vertigo
-fluctuating aural symptoms (HL, tinnitus, or ear fullness) in the affected ear
-other causes excluded by other tests
Characteristics of probable Menieres
-at least 2 episodes of vertigo or dizziness lasting 20 minutes to 24 hours
-fluctuating aural symptoms (HL, tinnitus, fullness) in the affected ear
-other causes excluded by other tests
Menieres HL characteristics
-HL
-low frequency SNHL initially, but declines with time across frequencies
-may not be the most disturbing symptom unless interferes with work
-reduced discrimination, tinny
-recruitment
-diplacusis (ears perceive different pitch)
Menieres fullness characteristics
-no objective measures for this so really have to rely on patients
-about 66% report
-associated with gait difficulties, drop attacks and hyperacusis
Menieres vertigo characteristics
-spinning when nothing is and neither are you
-earliest symptom
-usually lasts 1-2 hours but can last up to 24
-nausea, vomiting
-afterwrds, feel tired, unsteady, and nauseated
-periods of interim non-symptomatic
-triggers may be diet, menstrual cycle or stress
Drop attacks (Tumarkin crisis)
Usually mild (72%), 6% serious
Associated with utricular/saccular dysfunction
Describe the components of perilymph
Similar to CSF
High sodium and low potassium
Describe the components of endolymph
Similar to intracellular fluid
Low sodium and high potassium
Stria vascularis
What structure separates endolymph and perilymph
Membranous labyrinth
How do hydrops affect the membranous labyrinth?
Causes distortion of the structure
Pathophysiology of Menieres
-build up in pressure may lead to microtears of membranous labyrinth
-temporal bone histology (maybe due to degeneration but could be a secondary cause)
-vascular risk factors/ischemia
-fluid imbalance
-ion imbalance
-endolymphatic hydrops
Natural history of Menieres
-eventual resolution of vestibular symptoms
-57-60% of patients in 2 years
-71% in 8 years
-long term PTA in affected ear is about 50
-speech discrimination is about 53%
-caloric response reduction 50%
-vestibular function does not become normal
-symptoms decrease due to loss of function
-hearing issues will progress
-initial audio is tent curve
-5 years is sometimes peak and sometimes flat
-10 years is mostly flat curves
Diagnostic testing for Menieres
-unilateral vs. bilateral
-case history
-complete hearing eval including LDLs
-maybe vestibular testing like dix-hallpike
-maybe EcochG, ABR, EEG, DPOAEs, osmotic dehydration
-rule out tests: blood tests, allergy tests, MRI
Menieres and glycerol/urea/mannitol tests
-rarely done
-process:
-osmotic diuretics
-measure PTA or low/mid frequency thresholds
-patient ingests
-measure PTA or low/mid frequency thresholds
-compare PTA
-expectation is that it improves in Menieres, no change is not Menieres
EcochG and Menieres
-SP/AP ratio is greater than 0.5 or area ratio
-some labs report better sensitivity and specificity with more symptoms but variability
-recent work may improve sensitivity/specificity
What does new research show with Menieres?
-increased attention to vestibular, WAI and EP tests
-imaging
-endolymphatic sac surgery is back in China
-CI’s are a good option
New diagnostic approaches to Menieres
-high resolution MRI
-proteomics
-EvestG (electrovestibulography), similar to EcochG but with tilt and measure
-subjective visual vertical (SVV) perception
Gold standard for diagnosing Menieres
-imaging
-high pass masking of ABR (CHAMP), maybe this has not been able to replicate
-clinical history
-audiology eval
-exclude other conditions
Conservative management and treatment of Menieres
-minimize symptoms, particularly vestibular
-conserve hearing
-complications with this though: consistent diagnosis, fluctuation, assessing effectiveness and time frame
-conservative treatment has good results with about 85% of patients being helped
-lifestyle changes: regular meals, low salt, no MSG, no caffeine, no smoking, avoid triggers
Staging HL in definite/certain Menieres
-stage 1 is less than or equal to 25
-stage 2 is 26-40
-stage 3 is 41-70
-stage 4 is greater than 70
Medical management of Menieres
-diuretics and salt restriction (salt is believed to alter fluid balance in inner ear leading to depletion of endolymph)
-acute therapy: meclizine, benzodiazepines, corticosteroids, betahistine
-maintenance therapy
-vasodilators (allows the blood to slow more freely, allows for better metabolism of endolymph
-immunologic management (systemic steroids and intratympanic dexamethasone)
-steroids-intratympanic (autoimmune/inflammatory disease), lack of effect on hearing
-PE tubes
-antiviral drugs
-anti-nausea drugs
-homeopathy
-herbal (gingko)
-chiropractic
-acupuncture
-Meniett
-Intratympanic corticosteroids
-endolymphatic shunts
-intratympanic gentamycin
-endolymphatic sac vein decompression
Mechanical management of Menieres
-transtympanic micropressure
-Meniett device (portable low intensity alternating pressure generator)
Meniett
-has to be prescribed
-low frequency, low amplitude pressure pulses within the middle ear via a close-fitting ear cuff and tympanostomy tube
-use 3x a day, 3 minutes a session
Intratympanic treatment of Menieres
-purposefully damage the inner ear to stop vertigo
-injected through the TM using a narrow needle then the drug is left in the ME for a period of time then allowed to drain out
-destroys sensory cells
Intratympanic gentamicin for Menieres
-side effects can include temporary imbalance or nygstagmus, hearing loss
-often relieves symptoms but not always
Endolymphatic sac surgery
-addresses the site of obstruction causing hydrops
-different types:
-decompression
-shunting
-drainage
-removal of sac
-damage to sac
-blocking the sac
Vestibular nerve selection
-possible vestibular suppression without any effect on hearing
-single step procedure
-tricky and can have intraoperative complications of damage to facial nerve, cochlear nerve or CSF leak
Labyrinthectomy
-considered for patients with intractable vertigo and no functional hearing
-similar efficacy to vestibular nerve section
Menieres rehab
-physical/audiological issues:
-fluctuating HL
-tinnitus
-poor word rec
-rising configuration
-loss of dynamic range
-emotional issues:
-stress of illness
-restriction of activities
-vestibular rehab
Strategies for fluctuating HL
-hearing aids
-multiple memories to match the fluctuating hearing
Menieres counseling
-recognize emotional and social aspects
-reaosnable expectations
-support for identifying triggers
-reporting back
-use of earplugs
-support use of amplification
-support groups
Secondary endolymphatic hydrops
-trauma
-postoperative (CI, stapedectomy)
-otosclerosis
-CPA tumors
-other disease (autoimmune, infection)
-drugs (fluid balance)
Vestibular migraine
Vertigo, imbalance, dizziness, unsteadiness, motion sensitivity, muffled hearing, tinnitus, fullness
Genetic component for Menieres and vestibular migraines
5-20% familial for Menieres
Some families show a strong association with migraine
Maybe multifactorial
What is the most common vestibular disorder
BBPV
Mal de debarquement
Intense rocking, swaying sensation
Usually after a cruise
More common in women
Etiology unknown
May not resolve on its own
may resolve with vestibulo-ocular reflex reset
Chiari malformation
-1/1000 clinically
-type 1 may not be diagnosed
-symptoms include dizziness, muscle weakness, numbness, vision problems, headahce, progressive SNHL, tinnitus and problems with balance and coordination
-part of the cerebellum is displaced into the spine
-occipital headache with valsalva
-post surgery tinnitus
Perilymphatic fistula
-abnormal connection between inner and middle ear that allows leakage of perilymph
-like Menieres also a fluid imbalance
-unilateral HL, flucutating SNHL, sudden or progressive and/or fluctuating word discrimination, vestibular symptoms (vertigo, dysequilibrium, tullio, hennebert), tinnitus, aural fullness, flat tymps
Define vertigo
sensation of self-motion when no self-motion is occurring or the sensations of distorted self-motion during an otherwise normal head movement
Define dizziness
Sensation of disturbed spatial orientation without a false or distorted sense of motion
Most common etiologies of dizziness and vertigo
-physical trauma
-acoustic trauma
-barotrauma
-spontaneous
-ear surgery, particularly stapes surgeries
-neoplasms, cholesteatomas
-congenital, especially cochlear abnormalities