Ototoxicity

Ototoxicity (oh-tuh-tok-sis-i-tee) is damage to the hearing or balance functions of the inner ear caused by drugs or chemicals. The inner ear contains the hearing mechanism, the end organ of the balance mechanism and the vestibulocochlear nerve, which sends hearing and balance information to the brain. Damage to these areas by ototoxic drugs may cause loss of hearing, tinnitus (ringing or noise in the head or ears) and vertigo or sense of imbalance.
The extent of ototoxicity varies with the drug, the dose, duration of exposure and other conditions. In some cases, there is full recovery of any acquired hearing loss, tinnitus, or balance disturbance after the drug has been stopped. In other cases, the extent of damage is limited but permanent. An example of limited damage is high-frequency hearing loss, in which damage to the ear makes it difficult to hear high-pitched speech sounds such as “s,” “th,” “f” and “sh” and other high-pitched sounds such as musical notes or birds chirping. In more rare cases, there may be more wide spread hearing loss.

Many drugs can cause ototoxicity.  Patients receiving certain treatments known or suspected to have cochleotoxic or vestibulotoxic side effects (such as cisplatin, carboplatin, radiation, loop diuretics, or aminoglycoside antibiotics) may experience hearing loss, tinnitus, and dizziness/vertigo.  Cochleotoxic refers to medications that are toxic to the cochlea (the hearing portion of the inner ear) and vestibulotoxic refers to medications that are toxic to the vestibular (balance) portion of the inner ear.  Ototoxic medications can affect one or both portions of the inner ear.  The rate of ototoxicity is dependent on the drug dosage, whether the medication is given along with other ototoxic treatments, and other individual patient factors.

Other drugs and chemicals may also cause ototoxicity.  Hundreds of prescription drugs and over the counter medications are recognized as having the potential to be ototoxic and can result in temporary or permanent changes in hearing and balance function.  Aspirin overdose can cause ringing in the ears. The antimalarial drugs quinine and chloroquine may also cause ear damage. Among the environmental chemicals that can cause ear damage are: tin, lead, mercury, carbon monoxide and carbon disulfide. This list is not complete, and many other drugs and chemicals, such as industrial solvents, may cause ear problems.

Why Should Testing Be Completed?

Ototoxicity may often be undiagnosed as patients may not recognize the relationship between their treatment and the changes in their hearing and balance.   It is common for patients receiving ototoxic medications to report hearing loss, plugged sensations in their ears, ringing or buzzing noises, and mild to more significant balance concerns.  These changes can occur gradually and may be more difficult for a patient to notice.  This is why a pre-treatment baseline hearing test is recommended as well as monitoring hearing testing to track any changes that may be occurring. Monitoring any changes during treatment will allow your physician to determine if a change in medication, dosage or exposure time may be beneficial.

If permanent hearing loss does occur, an audiologist can counsel the patient regarding the hearing loss as well as offer strategies and options to improve hearing, communication and understanding.   Hearing Aids and other Assistive Listening Devices (such as amplified telephones) can be discussed and generally are fit on a 30 day trial basis.    

What Is An Audiologist?

Audiologists are professionals who specialize in the assessment, treatment and prevention of hearing and balance disorders. Our audiologists have a doctorate or master’s degree, hold a national Certificate of Clinical Competency in Audiology (CCC-A) and are licensed by the State of Wisconsin.

Ototoxicity Hearing Monitoring Program

Baseline Audiometry

Before receiving treatment involving therapeutic drugs known or suspected to have cochleotoxic side effects (such as cisplatin, aminoglycosides, or loop diuretics), the patient should undergo audiologic testing. Tests would include a Comprehensive Hearing Evaluation (including ultra high frequency testing) as well as Distortion Product Otoacoustic Emission (DPOAE) which evaluates the status of the outer hair cell function of the cochlea.

Ongoing Audiologic Monitoring

Ototoxicity protocols indicate the need for ongoing monitoring during treatments with ototoxic medications. These are usually scheduled 24 hours before each round of ototoxic medication, or weekly, depending on the type of medication the patient is taking. Because permanent drug-induced hearing loss may be delayed weeks or months after therapy, we continue to perform hearing evaluations immediately following completion of ototoxic drug therapy as well as at three- and six-month post-treatment intervals.

Counseling Regarding Communication

Every appointment with an audiologist includes counseling regarding any patient specific concerns.  It is important that patients are aware of how hearing and balance disorders can affect daily activities. Communication strategies and realistic expectations are an important part of living with hearing loss.

Hearing Preservation

It is important to limit your exposure of hazardous noise levels and wear hearing protection in loud environments. Prolonged exposure to loud sounds (whether you consider it noise or something more pleasant such as music) can worsen the effects of ototoxic drugs. Hearing protection should always be worn in the presence of these loud sounds, however, it is especially important during the entire course of cancer treatment and for at least 12 months after ototoxic therapy, to avoid the combined effects of high volume exposure and ototoxic drug therapy on the inner ear.   Custom-made and disposable ear protection is available through the Audiology Service at Froedtert Hospital.

Additional Audiology Services Provided

Hearing Aids and Assistive Listening Devices

Untreated hearing loss can have a negative effect on social interactions, occupational and educational success, and our general quality of life.   If the patient’s hearing loss indicates the need for hearing aids or assistive listening devices, the audiologist will evaluate your options and dispense high-quality devices through our clinic. Even if hearing aids are not used or recommended, there are many other assistive listening devices available for television, telephone, alarm clocks, smoke detectors and other alerting devices. 

Vestibular Evaluation

A person’s loss of balance can be discouraging and can cause difficulties in performing everyday tasks. The first step in monitoring and treating damage to the vestibular portion of the inner ear is to evaluate the person’s balance system. Common balance tests provided are Videonystagmography, Rotary Chair and Platform Posturography. Following these evaluations, a referral to an appropriate physician or rehabilitation program will be made.  Our facility has an onsite physical therapist that specializes in the treatment of certain types of dizziness and balance impairments.

Tinnitus Evaluation and Management

Tinnitus (ringing, buzzing or any other noises in the head or ears) can indicate that the outer hair cells of the cochlea (inner ear) have become damaged and/or that hearing loss has occurred.  Froedtert & the Medical College of Wisconsin have a Tinnitus & Hyperacusis Program with audiologists that specialize in the evaluation and treatment of tinnitus.  For those patients whose tinnitus is not medically remediated, the audiologists at Froedtert & Medical College of Wisconsin can provide patients with treatments and tools to obtain control and relief of their tinnitus.

Contact/Scheduling Information

Please inform the scheduler that your appointment is for ototoxicity. Baseline and follow-up evaluations for ototoxicity are given special scheduling consideration.  We will work with the patient to ensure their tests are performed prior to their next scheduled cancer treatment.