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 - Age The 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 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 test R/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 Sudden hearing loss Presbyacusis 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.