Ototoxicity

Question 1

What is ototoxicity?

Answer 1

An undesired effect of a substance (drug or chemical agent) on the auditory or vestibular system

Question 2

What are the two types of ototoxicity?

Answer 2

Cochleotoxic: cochlea
Vestibulotoxic: vestibular

Question 3

What are the types of ototoxic medications?

Answer 3

Chemotherapy and antibiotics

Question 4

How does ototoxicity occur? What determines the degree of damage?

Answer 4

• Toxic agents are carried via the blood supply into the perilymph and endolymph to the sensory cells
• Degree of damage is determined by toxicity of the agent, duration of exposure, individual susceptibility, previous use of ototoxic drugs

Question 5

What kind of hearing loss do aminoglycoside antibiotics cause?

Answer 5

SNHL, permanent in 2-5% of patients

Prolonged exposure causes programmed cell death (apoptosis)

Question 6

Aminoglycoside antibiotics typically cause damage to …

Answer 6

OHCs, supporting cells, stria vascularis, spiral ganglion cells, basilar membrane collapse
DOES NOT AFFECT IHCs

Question 7

What type of hearing loss do loop diuretics cause?

Answer 7

SNHL, immediate, precipitous (steeply sloping audiogram), usually temporary due to swelling of stria vascularis
Most dangerous when loop diuretics are given via IV

Question 8

Salicylates (like aspirin) cause what type of hearing loss?

Answer 8

SNHL, usually temporary

Toxic in high doses

Question 9

Anti-neoplastic drugs also referred to as chemotherapy cause what type of hearing loss?

Answer 9

SNHL, permanent

Occurs in about 90% of patients

Question 10

How does chemotherapy causes hearing loss?

Answer 10

Toxin enters all cells in the cochlea and destroys them at the level of the organelles causing premature death

Question 11

What is the primary site of lesion for chemotherapy?

Answer 11

Hair cells (IHC and OHC)

Question 12

Symptoms of cochleotoxic vs vestibulotoxic otoxicity

Answer 12

Cochleotoxic: Typically high-pitched tinnitus, Tinnitus may precede hearing loss

Vestibulotoxic – vertigo/dizziness/unsteadiness

Question 13

Ototoxicity effect on otoscopy and tympanometry

Answer 13

Both WNL

Type A tymps

Question 14

Ototoxicity effect on acoustic reflexes …..

Answer 14

Consistent with degree of hearing loss

Meaning will be present if SNHL below 50 dB and absent if SNHL greater than 50 dB

Question 15

Ototoxicity presentation on the audiogram

Answer 15

SNHL that begins as high-frequency

Worsens with increased or prolonged dosages

Question 16

With ototoxicity, the onset of hearing loss ….

Answer 16

May appear shortly after the administration of the drug

May not appear until several months or even later after administration has ceased (toxins lingering in the body)

Question 17

Ototoxicity effect on OAEs

Answer 17

Wipes out OAEs, typically the first to go