Ototoxicity, Presbycusis and Noise Induced Hearing Loss Flashcards
Ototoxicity HL induced by
medications (& others)
Presbycusis HL associated with
aging
Noise-induced hearing loss (NIHL) HL induced by
noise exposure
Who is affected by ototoxicity, presbycusis, and NIHL?
Ototoxicity
Adults and children (high-risk register)
Presbycusis
Adults
Noise-induced hearing loss (NIHL)
Adults and children
How can ototoxicity affect cochleovestibular function?
Partial or total reduction of cochleovestibular function from exposure to toxic chemical substance
What are teratogens?
substances that cause birth defects
What is latrogenic?
complications caused by medical or surgical intervention (caused by HCP)
Ototoxicity =
Ototoxicity = iatrogenic
Do all patients who take ototoxic medications usually get HL?
Not all patients who take ototoxic medications will get hearing loss
Degree of ototoxicity varies
What are the susceptibility risk factors of ototoxicity HL?
Pre-existing hearing loss
Age
Renal function
Drug dosage
Method of administration
Susceptibility risk factors related to:
Mitochondrial gene mutation (12S ribosomal RNA gene in Chinese)
Ototoxic HL presents with: (5)
SNHL
Tinnitus
Dizziness/imbalance
Nausea
Reduced speech discrimination
Give 5 medications that cause ototoxic HL:
Aminoglycosides (antibiotics)
Diuretics
Salicylates
Antimalarial agents
Chemotherapeutic agents
When do we use aminoglycosides?
Commonly used to treat gram-negative bacteria associated sepsis
- UTI or pneumonia
Aminoglycosides are usually given:
IV lines
Poorly absorbed through GI tract
Rarely given as ototopical drops
How do Aminoglycosides affect IE structures?
Directly damage inner ear structures
- Cochlea
Basal turn > apical turn
Outer hair cells > inner hair cells > stria vascularis - Vestibular organ
Utricle and saccule
Vertigo/dizziness may be present
How does ototoxic HL due to aminoglycosides appear on the audiogram?
High frequency affected first (> 8 KHz)
May not initially be detected by audiogram
Bilateral SNHL
Irreversible
Acute or chronic loss
Aminoglycosides: Neomycin and Kanamycin
are more likely to cause________________
cochlear toxicity first
Aminoglycosides: Gentamycin and Streptomycin are more likely to cause________________
to cause vestibular toxicity first
Intratympanic therapy used in severe Meniere’s disease (close monitoring required)
When used in early pregnancy, some aminoglycosides may cause ______________________________________________________
When used in early pregnancy, some aminoglycosides may cause ototoxicity and other congenital anomalies in the newborn
How do diuretics affect your system and hearing?
Affects the fluid flow in your body
Damages the stria vascularis
Tinnitus and vertigo
May be temporary/reversible SNHL
High doses can cause permanent SNHL
Salicylates are commonly found in ________________________ and ____________________________
Salicylates are commonly found in antipyretics and analgesics
Antipyretics are:
Antipyretics-fever relieving drugs
Analgesics are:
Analgesics-pain relieving drugs
How do salicylate drugs affect hearing?
Mechanism of HL
Reduced blood flow to cochlea
(No hair cell loss)
What are features of salicylates hearing loss?
Common cause of high frequency tinnitus
Reversible, mild to moderate SNHL (rarely permanent)
What are antimalarial agents? (3)
Not commonly used in North America
Originally thought malaria caused hearing loss but it was the drug to treat malaria
Hearing loss depends on the dose
How do Quinine drugs affect hearing?
A similar mechanism as aspirin
Reduced blood flow to the cochlea
Reversible, bilateral SNHL
Rarely dizziness
High-pitched tinnitus
What are Chemotherapeutic Agents?
Systemic cancer treatment drugs
Most agents kill cells that divide rapidly (main properties of cancer cells)
Other normal cells that divide rapidly include bone marrow, digestive tract and hair follicles
They are also targeted
Chemotherapeutic Agents affect
Bone marrow causing:
Digestive tract:
Hair follicles:
Bone marrow causing: immunosuppression
Digestive tract: mucositis (inflammation of lining of GI tract)
Hair follicles: hair loss
In Chemotherapeutic Agents, what are the two platinum-containing agents?
Cisplatin
Carboplatin
Binds to DNA and interferes with normal repair mechanism
Mostly used in breast, head/neck, and ovarian cancers, lymphomas
How does cisplatin affect hearing? (3)
HL is dose dependent
Damages the cochlear hair cells starting at the basilar end
Stria vascularis also damaged
Risk of Ototoxicity from:
Aminoglycosides =
Diuretics =
Aspirin =
Cisplatin=
Aminoglycosides = 5-10% in ICU patients
Diuretics = 1-5%
Aspirin = <1%
Cisplatin= >50% (dose-dependent)
What are other causes of ototoxicity? (6)
Anticoagulants (blood thinners)
Anticonvulsants (seizure medications)
Beta blockers (heart medications)
Topical antimicrobials
Alcohol (fetal alcohol syndrome)
Radiation therapy
What are topical antimicrobials? (3)
Commonly prescribed for otorrhea
Garamycin, gentamycin, neomycin
Agents may enter the middle ear through TM perforations and eventually enter the inner ear, causing SNHL
What is fetal alcohol syndrome?
A recognizable pattern of congenital anomalies seen in children of women who use (abuse) alcohol during pregnancy
What are the clinical features of fetal alcohol syndrome? (5)
Dysmorphic characteristics (craniofacial anomalies)
Growth deficiency (low birth weight, failure to thrive)
Organ system defects (heart problems, GI issues)
CNS dysfunction (intellectual disability, hypertonia)
Hearing disorders (SNHL, CAPD, ± CHL)
What is radiation therapy?
Used in treating cancers
Ionizing radiation damages DNA
What are other sources of radiation? (3)
Nuclear power plant
Multiple x-rays, CT scans
Submarines, military
Which cancers tend to receive radiation treatment?
Head and neck cancers tend to receive radiation treatment
What is synergistic effects?
can occur when patients receive radiation and chemotherapy
How does radiation therapy affect hearing? (2)
SNHL
Atrophy of organ of Corti, spiral ligament, and stria vascularis
CHL
Otitis externa, EAC/middle ear damage, OME
What is Presbycusis? (2)
Progressive deterioration of hearing associated with aging
Most common cause of adult hearing loss
> 50% of elderly have presbycusis
What is apoptosis?
Process of programmed cell death
Part of normal aging in organisms
Orderly process ensuring renewal of cells
But over time, it results in aging
What occurs in apoptosis?
Billions of cells die daily in adult humans
Malignancies are thought to be related to a disruption of this process
What occurs in necrosis?
Cell death due to injury
Not a normal process (ototoxicity and NIHL)
How does presbycusis affect hearing?
Cumulative effect of aging
Apoptosis of auditory cells
Bilateral, symmetrical, progressive, and irreversible
The degree of loss is variable between individuals
What is the epidemiology of presbycusis? (4)
Prevalence is equal between males and females
Extent of HL worse in men
Rate of decline worse in men
Earlier onset HL in men
How does presbycusis affect structures in the IE and how does it look on the audiogram?
Loss of hair cells (basal end of the cochlea)
Flattening of the organ of Corti
High-frequency hearing loss
Reduced speech discrimination
What is Neural presbycusis? (4)
Damage and loss of cochlear neurons
Starts earlier in life and is progressive but pure tone thresholds are unaffected until later
Lower and higher frequencies involved
Marked reduction in speech understanding (central etiology)
How does presbycusis affect the Strial vascularis?
Strial presbycusis
1. Damage to stria vascularis
2. Occurs at both high and low frequencies
3. Hearing loss begins at 30s-40s and progressive
4. Good speech discrimination
5. Responds well to amplification
Explain undefined presbycusis:
About 25% have no distinguishable characteristics
No specifically defined problem
Specific types of presbycusis deal only with ______________________________________________________
age-related changes to the cochlea and 8th nerve
What are other aspects of age-related hearing changes?
Central auditory processing delays
Recruitment
Reduced sound localization abilities
Reduced speech perception in noise
What could be age-related ear changes at the level of the EE, ME and IE?
External ear
Elongation of lobule
Calcification of ear cartilage
Middle ear
Reduced blood supply to TM (stiff)
Increased density of ossicles
Inner ear
Hair cell changes
What are other aging changes?
Loss of muscle tone
Skin changes
Neurologic changes
Presbylarynges
Against NIHL:
OSHA regulations
Exposure equivalent above ____dBA time-weighted average for ___hours requires hearing protection programs
95 dBA for_______________
100 dBA for ___________
130 dBA for ___________
OSHA regulations
Exposure equivalent above 85 dBA time-weighted average for 8 hours requires hearing protection programs
95 dBA for 4 hours
100 dBA for 2 hours
130 dBA for < 2 mins
What is TTS?
Temporary SNHL that resolves within 24 hours
Intense, short duration of exposure
What is PTS?
Permanent SNHL
Chronic exposure
What could be work-related risks NIHL in adults?
Factory workers
Military
Heavy machinery
What could be work-related risks NIHL in adults?
Factory workers
Military
Heavy machinery
Guns
Estimates suggest up to ______% of children will experience NIHL
Estimates suggest up to 15% of children will experience NIHL (ex: from toys)
Explain the culture of noise from NIHL like fitness clubs, movies and concerts:
Fitness clubs
Noise measured at 90 clubs across USA
Levels reached 120 dB
80% reached 100 dB for 1 hour classes
Movies
Armageddon: 117 dB shuttle take off scene
Godzilla: 115 dB shriek
Concerts
Standard rock concert level is 125 dB
Consider hearing protection at rock concerts
How does NIHL mechanically damage our hearing organs?
Outer hair cell damage from chronic loud noise due to oxygen radical formation
Single intense exposure (eg explosion, gunfire) may mechanically damage the organ of Corti or rupture cochlear membranes
What are the features and diagnosis of NIHL?
SNHL (mostly bilateral)
High-pitched tinnitus
History of noise exposure
Audiogram
How can we manage NIHL?
Hearing conservation programs having for objective to reduce the risk of developing a permanent NIHL
What are the elements of the hearing conservation program?
Noise measurement and reducing exposure
Audiometric testing
Employee training and education
Record keeping
Program evaluation
How can we reduce exposure to loud sounds for NIHL?
Repair or change machinery
Isolate worker from machinery
Limit time exposure to noise
Ear protection
What is the purpose of audiometric testing?
Identify significant threshold shift
Monitor the effectiveness of the hearing conservation program
Establish readiness and fitness for work
Ensure proper referral and diagnosis
What is pseudohypocusis?
Pseudo-false or fake
Aka-functional hearing loss
Subjective loss of hearing by a person with absence of organic pathology
What are clinical features we see in pseudohypoacusis?
Suspect when the patient hesitates, shifts pure tone thresholds or expresses confusion
PTA at 500, 1000, and 2000 Hz should be within 10 dB of SRT
Acoustic reflexes should be absent if tests suggests significant hearing loss
Normal ABR/OAE
Why would people fake a hearing loss?
Mostly deliberate for psychological reasons or for compensation
Rarely it is unrealized by the client
How do you test for pseudohypacusis?
OAE
ABR
Startle or gentle confrontation
Stenger’s test
Lee’s speech delay test
Lombard test
How does the stenger test work?
2 tones of same frequency presented to each ear cannot be heard simultaneously if one is louder
Client given 2 simultaneous tones with matched frequency but the alleged poorer ear receives louder tone
For real HL, the tone should be heard in the better ear
Fakers will report hearing nothing
How does Lee’s speech delay test works?
Client is played back his or her own speech at a delay that would cause the subject to stutter
How does the Lombard test work?
Background noise is gradually introduced below the client’s recorded response threshold as the client is asked to read aloud
Volume of the reader’s voice increases as the masking noise is presented in pseudohypacusis
