A&P Exam 3 Topic 14: Trauma, Ototoxicity, Fistula, Sudden SNHL & BPPV

Traumatic head injuries can cause which types of hearing loss?

• Conductive

• Sensorineural

• Mixed

Give examples of head trauma that can cause hearing loss

• Concussion

• Bleeding in the ear

• Temporal bone fracture

• Airbag deployment: enough sound pressure to perforate the eardrum (especially the driver)

Trauma: what causes the conductive hearing loss?

• Tympanic membrane tear

• Injury to the ossicles

Trauma: what causes the sensorineural hearing loss?

• Concussion to the inner ear

• Temporal bone fracture directly injuring the inner ear

What are the two types of trauma that cause hearing loss, with an example of each?

• Acoustic trauma: bomb blast, firework, firearm blast

• Physical trauma: traffic accident

How is physical trauma to the temporal bone classified?

By the fracture line, in reference to the petrous pyramid axis

Which temporal bone fracture more likely causes conductive hearing loss?

Longitudinal fracture

Longitudinal temporal bone fracture: what conductive damage can it cause?

• Tympanic membrane tear

• Ossicular chain discontinuity (OCD)

• Hemotympanum (blood inside the tympanum)

Which temporal bone fracture causes sensorineural hearing loss?

Transverse fracture

Transverse temporal bone fracture: which structures are injured?

• Cochlea

• Vestibular system

• Auditory nerve

Longitudinal temporal bone fracture: example

Bat throwing

Transverse temporal bone fracture: example

Getting mugged

What must happen after a traumatic brain injury?

Refer for hearing testing

What percentage of temporal bone fractures are longitudinal?

80%

How can a longitudinal fracture still produce sensorineural hearing loss?

Through inner ear concussion

Define concussion

• A violent shock, as from a heavy blow

• May lose consciousness for some period of time (non-specific)

Transverse fractures: what do they cut through, and what do they cause?

• Cut through the inner ear

• Often cause profound sensorineural hearing loss and vertigo (vestibular)

In what percentage of transverse trauma patients is facial paralysis seen?

50%

Besides longitudinal and transverse, what other fracture type is also common?

Mixed fractures

Trauma: how is conductive hearing loss treated, and what is the prognosis?

• Surgical correction of middle ear damage

• Prognosis good

Trauma: what is the outlook for sensorineural hearing loss?

• Often permanent

• No medical treatment available

• Hearing aids or a cochlear implant may help

Define ototoxicity

Damage to the ear due to the toxic effects of various chemical agents, especially drugs

Which class of antibiotics contains the most ototoxic medications?

• Aminoglycosides (gentamycin, amikacin, kanamycin, etc.)

• Delivered by IV

When are aminoglycosides generally given?

• Very severe or life-threatening infections

• Newborns in a state of sepsis

Which chemo drugs are very ototoxic, and what do they cause?

• Cisplatin and carboplatin (renal cancer)

• Severe hearing loss

Describe ototoxic monitoring

• Pre-test for a baseline

• Test after each dose

• By the 2nd-3rd dose there may be moderate to moderately severe hearing loss: fit flexible hearing aids

Salicylates (aspirin): when are they ototoxic, and is the loss permanent?

• Ototoxic in large doses

• Hearing loss usually reversible (if you stop taking it)

Name the loop diuretics listed as ototoxic

• Bumetanide (Bumex)

• Ethacrynic acid (Edecrin)

• Furosemide (Lasix)

Loop diuretics: is their ototoxic effect permanent, and what are they used for?

• The effect can be reversible

• Treat congestive heart disease (heart failure) and kidney dialysis

Besides antibiotics, aspirin and diuretics, which drugs are proven to affect hearing?

Drugs used to treat cancer

List the ototoxic chemicals

• Heavy metals (e.g., mercury)

• Tetrachlorocarbon

• Organic phosphates (fertilizers)

• Carbon monoxide (vehicle emissions)

What can exposure to ototoxic chemicals at industries or home lead to?

Sensorineural hearing loss

Which systems do ototoxic chemicals generally affect?

Both the cochlear and vestibular systems

Which drug is cochleotoxic?

Neomycin

Which drug is vestibulotoxic?

Streptomycin

Ototoxicity: list the signs and symptoms

• Bilateral hearing loss (sometimes unilateral), high frequencies affected first

• Tinnitus

• Vertigo, general unsteadiness

• Symptoms soon after drug administration; effect can last for months after the drug stops

Ototoxicity: treatment

• Closely monitor the patient to detect ototoxicity

• Change dosage, stop the medication, change the drug combination or frequency

Define perilymphatic fistula

• Leak of perilymph due to rupture of the oval or round window

• Can be small, even microscopic

Define barotrauma

Injury from a rapid change in pressure

List the causes of perilymphatic fistula

• Explosions

• Barotrauma

• Increased intracranial pressure from straining or physical exertion, sneezing, coughing, Valsalva maneuvers

• Cholesteatoma

• Side effect of surgery

Perilymphatic fistula: symptoms

• Vertigo and nystagmus when pressure increases in the ear canal

• Sudden hearing loss

Define nystagmus

• Rapid back-and-forth movement of the eyes

• The eyes trying to compensate because you're dizzy

Which condition shows twisting nystagmus?

BPPV

What three systems are required to maintain balance?

• Eyes (ocular system)

• Ears (vestibular system)

• Somatosensory system / proprioception (where you are in space)

Define sudden sensorineural hearing loss (SSNHL)

• Hearing loss greater than an average of 30 dB HL

• At three contiguous frequencies

• Occurring in less than three days

How urgent is sudden sensorineural hearing loss, and what is needed?

• Considered a medical emergency

• Requires steroids immediately

SSNHL: what is the pathogenesis?

Multi-factorial: viral infections, affected blood supply, perilymphatic fistula, tumor, trauma, etc.

SSNHL: when does spontaneous improvement occur?

Over the first two weeks after onset

SSNHL: how does symptom duration affect prognosis?

• Prognosis gets worse the longer symptoms persist

• No recovery in the first 2 weeks means minimal chance of recovery

SSNHL: expected presenting complaints

• Unilateral hearing loss

• Tinnitus (70% of patients)

• Vertigo (50% of patients)

• Often report waking up with a hearing loss

SSNHL: what is it often blamed on, and is that correct?

• Autoimmune disorders (e.g., lupus)

• But it is not

SSNHL: expected past medical history

• Diabetes

• Syphilis

• Chronic renal disease

• Cardiovascular disease

SSNHL: expected signs on physical examination

Nothing in particular

SSNHL: expected audiologic test results

• Unilateral sensorineural hearing loss

• Tympanograms normal

• Otoacoustic emissions consistent with the degree of loss

• ABR: wave latency prolonged, amplitude decreased, morphology variable

• ENG: calorics may show decreased function on the affected side (or contralateral, depending on etiology)

SSNHL: which audiogram patterns have a poor prognosis?

• Downward sloping

• Flat moderate

• Severe loss

SSNHL: which audiogram pattern has a better prognosis?

Mild low-frequency loss

Sudden hearing loss: list the referrals

• Physician

• Neurological examination

• Radiology examination

• Pathology (infections, hormones, etc.)

SSNHL: expected medical treatments

• Corticosteroids (prednisone)

• Vestibular suppressants (prescription strength Dramamine)

SSNHL: when is surgery expected?

None, unless there is a perilymphatic fistula

SSNHL: expected long-term sequelae

• Recovery of hearing: complete, partial or non-existent

• Vestibular symptoms usually subside

• Hearing aids may be helpful

What causes benign paroxysmal positional vertigo (BPPV)?

• Dislocation of otoconia in the vestibular system

• Otoconia fall off into the fluid of a semicircular canal and send signals to the brain about movement the body isn't doing

BPPV: what happens when the person changes body position?

• The otoconia move inside the ear, causing a sensation of movement or vertigo

• Only in the offending ear; makes the person violently dizzy

BPPV: list the symptoms

• Vertigo when body position changes

• Nausea and vomiting

• Visual problems: things seem to move or jump

• Hearing loss (very rare)

BPPV: who gets it, and can it be prevented?

• Common in people in their 40s and 50s; can be episodic

• Not preventable; very common

Which test checks for nystagmus in BPPV?

Dix-Hallpike test

BPPV: list the causes

• Head trauma

• Activities with sudden high intensity (brisk) head movement: bike riding on rough trails, high intensity aerobics

• Aging (increases susceptibility)

• Other inner ear disease (ischemic, inflammatory, infectious)

BPPV: treatment and an example

• Vestibular therapy

• Example: Epley maneuver

Conductive hearing loss: site of lesion

Outer and/or middle ear

Sensorineural hearing loss: site of lesion

Inner ear

Conductive hearing loss: list the difficulties

• Less sound transmission; sound reaching the inner ear is weaker

• Difficulty hearing soft to moderate sounds

• Speech understanding not affected

• Treated with a hearing aid

Sensorineural hearing loss: list the difficulties

• Less sound transmission; sound reaching the brain is weaker

• Difficulty hearing soft to moderate sounds and tolerating loud sounds

• Poor speech clarity; difficulty understanding speech

• Difficulty understanding speech in background noise