MANAGEMENT OF OTOTOXICITY OUTLINE• History• Examination • Investigations• Diagnosis• Differential diagnosis• Prevention and monitoring• Treatment• Prognosis• Follow up• Recent advances• Conclusion

HISTORY

Detailed history is required to - Establish a diagnosis - Ascertain severity of the condition - Identify those at risk

Bio data - AgeThe following symptoms are looked out for and

evaluated > Tinnitus – most often the first symptom > Hearing loss > Imbalance or vertigo

> History of intake of ototoxic drugs (type, dose & duration).

> History of risk factors -- impaired renal function -- impaired liver function --history of previous intake of ototoxic

agents -- family history of ototoxicity Recent organ transplantation.

Examination General examination Ear examination -- otoscopy- usually normal except in pre existing

pathology like csom – TM perforation ± discharge etc -- Tuning fork test -SNHL -Rhinne test –positive - Weber test – lateralized to better ear

Vestibular function test – for those who present with vertigo or sense of imbalance.

- Hallpike manoeuvre - Romberg testR/o other causes of vertigo -fistula test

Investigations• Pure tone audiometry – High frequency• Otoacoustic emissions• Brainstem evoked response audiometry• Electrocochleography – measures the signals

produced by the cochlea and cochlear nerve in response to acoustic stimulus

• Caloric test - canal paresis - unilateral preponderance

Diagnosis

From history - reveals intake of ototoxic medication

• Diagnosis is by exclusion• OAEs, high frequency PTA, BERA &

electrocochleography reveal cochlear damage but not specifically ototoxicity

Differential diagnosis

I. Sudden hearing lossII. PresbyacusisIII.Acoustic neuroma.

Prevention and monitoring• Ototoxicity is preventable• Ototoxic damage is often times irreversible • Treatment poses a great challenge• Prevention is therefore highly advocated

Measures• Avoidance of ototoxic drugs• Awareness – clinicians should be aware of drugs with

ototoxic potentials

• Recognition of at risk groups e.g. - previous history of ototoxicity - family history of ototoxicity - elderly - impaired kidney or liver function - patients already on ototoxic medication. Recent organ transplantation

Recognition of at risk group allows the modification of therapeutic regimen.

• Protection against ototoxicity.• - Co-administration of antioxidants or iron

chellators. • - otoprotective agents; vitamin A, alpha

lipoic acid, gingko biloba.• - study by Kocyigit et al suggested that the

antioxidant N-acetyl- cysteine can protect against Amikacin toxicity

• Avoidance of noisy environment.• Monitoring of serum levels of ototoxic agents.• Audiologic monitoring. - Pure tone audiometry - Otoacoustic emissions - Brain stem evoked response audiometry. - Electrocochleography• No official guideline for audiologic monitoring.• Routine monitoring is unnecessary unless patient is

at risk of ototoxicity.• Interval of testing should decrease with the first sign

of ototoxic damage.

TREATMENT• Medical - labyrinthine vasodilators. - labyrinthine sedatives - tinnitus maskers - vestibular rehabilitation exercises.• Amplification – use of hearing aids.• Surgical - Cochlea implants.

PROGNOSIS• Depends on ; - the ototoxic agent. - nature of ototoxicity- reversible,

irreversible, progressive. - severity of the toxicity.• For those that can benefit from amplification,

prognosis is good.• Cochlear implant where available and

affordable increases prognosis.

RECENT ADVANCES.Hair cell regeneration. - Possibility of hair cell recovery is recently an

area of active interest. -Avian inner ear has demonstrated regenerative

capacity of hair cells after gentamicin exposure. - Role of regenerated hair cell in relation to

functional recovery is yet to be clearly defined. -Further studies needed.• Otoprotection. - another area that requires further study.

• CONCLUSION.• Ototoxicity is a preventabe cause of

severe morbidity which is usually difficult to manage.

• The emphasis should be on prevention.