Ototoxicity

Ototoxicity is the term used when a substance has the property of being toxic to the inner ear.  Ototoxicity includes the hearing and vestibular portions of the inner ear. When the damage is restricted to the vestibular organ it is coined vestibulotoxicity.

Ototoxicity

Ototoxic medication can damage the haircells of the Organ of Corti in the inner ear.

The toxic damage that occurs within the inner ear include reversible and irreversible structural damage to the hair cells and other parts of the Organ of

Corti the vestibular organ and in rare cases the nerve.

Ototoxic agents include systemic and locally applied agents. Systemic ototoxicity refers to medication or toxins that is absorbed and then has a damaging effect on the inner ear. Luckily some of these drugs have reversible effects but unfortunately only some. A lot of medication that is ototoxic, unfortunately needs to be taken by a patient for a more serious, often life threatening condition.

Some of the most common ototoxic medication include:

  • antibiotics such as aminoglycosides and macrolides
  • loop diuretics (water pills) such as furosemide
  • chemotherapeutic agents such as Cisplatin
  • nonsteroidal anti-inflammatories (NSAIMS)
  • anti-malarial drugs

Ototoxic toxins include solvents, heavy metals such as mercury or lead and toluene. Local ototoxic agents include some antibiotic drops and cleaning agents such as alcohol inserted directly into the ear.

Ototoxicity presents with hearing loss, tinnitus and balance impairment. Balance impairment or disequilibrium is far more common than rotational vertigo. Oscillopsia (jumbling of the panorama) is a characteristic problem of patients with bilateral vestibulopathy due to ototoxicity. Whenever these patients move the whole world seems to move with them, only stabilizing when they stand still!

The diagnosis of ototoxicity is made with audiological and vestibular testing. High frequency audiometry, oto acoustic emissions may pick up early hearing loss whilst vestibular testing in the form of videonystagmography, (VNG), video head impulse testing (VHIT) and rotation chair testing will show vestibular damage.

Patients with hearing loss or vestibular damage due to ototoxicity should refrain as far as possible to use any ototoxic (and vestibulotoxic) medication. Care should be taken not to insert any drops into the ear without consulting a doctor. Hearing loss may be addressed with hearing aids and if severe with cochlear implantation(CI).

Vestibular loss is a bigger problem. For those with vestibular loss vestibular rehabilitation may be the only solution. Although a lot of experimental work is done on a vestibular implant it is not freely available on the market yet. As with a cochlear implant it aims to substitute the damaged vestibular end organ.

Many options for tinnitus exist, including tinnitus retraining therapy (TRT) with “you have to live with it” not one of them.

Further reading

An overview of pharmacotherapy-induced ototoxicity

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