Ototoxicity is a medical term for ear poisoning. It is diagnosed when you have hearing issues or balance problems due to a high dose of certain medicines. Drugs that treat cancer, infections, and other serious health issues can cause ototoxicity.
Early diagnosis and treatment can prevent the condition from worsening, though.
What Is Ototoxicity?
Some medicines can damage your ear and lead to hearing loss or balance problems. They are known as ototoxic medicines or ototoxins. Ototoxicity occurs when you get ear poisoning due to such medications.
Ototoxicity symptoms can be reversed when you stop taking the underlying medication, but if the condition is not treated immediately, you may suffer permanent ear damage.
What Are Ototoxicity Causes?
More than 200 known ototoxic medications exist on the market. These medicines are used to treat serious infections and illnesses like cancer and heart disease.
Unfortunately, they can be toxic for sensory cells present in the inner ear. Sensory cells are responsible for hearing and balance. Ototoxic medicines damage these cells, resulting in hearing and balance problems.
Ototoxicity causes include the following medicines:
1. Aspirin.Aspirin is known to cause ototoxicity and ringing in the ears, or tinnitus. If you have high doses of aspirin, you can develop hearing loss.
2. Quinine. In high doses, quinine can cause temporary loss of hearing and balance. Quinine products that cause ototoxicity include chloroquine, quinidine, and tonic water.
3. Loop diuretics. These drugs are called “ water pills” because they help clear water from your body. They can cause ototoxicity. They lead to ringing in the ears or hearing loss. These symptoms are temporary and can be reversed when diuretics are discontinued. Ototoxic diuretics include bumetanide, ethacrynic acid, furosemide, and torsemide.
4. Aminoglycoside antibiotics. Aminoglycoside antibiotics are well-known ototoxins. If they enter the inner ear, they cause hearing loss and balance problems. Aminoglycoside antibiotics like amikacin, netilmicin, gentamicin, kanamycin, and neomycin can cause ototoxicity.
5. Anticancer drugs. Anticancer or chemotherapy drugs can kill other cells along with cancer cells. They can be ototoxic and damage the sensory cells in the inner ears. Anticancer drugs like Cisplatin and Carboplatin are well known to cause ototoxicity and hearing loss.
6. Environmental chemicals. Environmental toxins can cause ototoxicity and lead to permanent hearing problems.
Environmental ototoxins include:
- Mercury
- Tin
- Lead
- Toluene
- Manganese
- Butyl Nitrite
- Hexane
- Styrene
- Xylene
- Carbon Disulfide
- Carbon Monoxide
- Trichloroethylene
What Are the Risk Factors of Ototoxicity?
The risk of ototoxicity depends on the type of medicine you’re taking, its dose, and how long it’s been in your body.
The risk of ototoxicity increases if you take a combination of ototoxic medicines. For example, taking loop diuretics along with aminoglycoside antibiotics can cause ototoxicity. If you have kidney problems or are taking medicines that affect kidney function, taking aminoglycosides can increase your risk of developing cytotoxicity.
Sometimes, you may have to take an ototoxic medication to cure a serious illness, but check with your doctor about the risk of ototoxicity beforehand.
What Are Ototoxicity Symptoms?
Ototoxicity symptoms can start suddenly or develop slowly over time. Usually, the first sign of ototoxicity is tinnitus or ringing in the ears. Tinnitus causes buzzing, hissing, or humming sounds in your ears.
Ototoxicity symptoms include hearing loss. This can cause difficulty while communicating in daily life.
You’ll also feel dizzy or unsteady and lose your balance. Such symptoms may be temporary, but they can be debilitating in some cases.
The severity of balance problems due to ototoxicity depends on these factors:
- The amount of damage done by the ototoxins
- How long ago the damage started
- Whether the damage is rapid or slow
- Whether it affects one or both ears
Slow damage on one side may not cause dramatic symptoms, but rapid damage can cause vertigo, vomiting, and eye jerking or nystagmus. These symptoms may become less severe over time.
Severe ototoxicity, though, can cause long-lasting symptoms. When both your ears are affected, you may notice these symptoms:
- Headache
- Imbalance
- Oscillopsia (i.e., bouncing or blurry vision when you move your head)
- Feeling that your ears are full
- Difficulty walking
- Inability to move your head
- Walking with your legs too far apart to maintain your balance
- Trouble walking in the dark
- Feeling unsteady, lightheaded, and tired
How Is Ototoxicity Diagnosed?
If you notice ototoxicity symptoms, you’ll have to visit an audiologist, a doctor who treats hearing and balance problems. They’ll ask you what medicines you’re taking and record your baseline hearing and balance using tests.
Ototoxicity diagnosis involves the following tests:
Audiometric or behavioral hearing tests. These hearing tests check the sounds that you can or can’t hear. Your audiologist will use pure tones, high-pitch sounds, word recognition, and other tests. They will continue to monitor and compare the results during your drug therapy. Based on the test, your doctor will decide whether to stop or change your medicines before they potentially cause ear damage.
Auditory brainstem response (ABR) test. For this test, small earphones are placed in the ear canal, and electrodes or small stickers are placed on the scalp and behind the ears. The electrodes measure the signals from the auditory nerve and parts of the brainstem responsible for hearing.
Otoacoustic emissions (OAE) test. A tiny instrument called a probe is placed in the ear canal. Sound waves are passed through it. The probe records the echo or reflection of the sound waves from the inner ear cells. If the recording is normal, the inner ear is not damaged. OAE and ABR are used to check for hearing problems in babies and young children.
Tympanometry. This test checks if sound moves through the eardrum and ear bones by creating air pressure variations in the ear canal.
Electronystagmogram. This test is used to check your balance and whether you have vertigo or nystagmus. A computer records your eye movements to see if you have balance problems.
Posturography. This test checks how well you can balance while standing on stable or unstable platforms.
Questionnaires. Your doctor may ask you to fill up questionnaires related to balance, dizziness, and other symptoms during daily activities.
Other tests. Your audiologist may also use tests like vestibular autorotation test, vestibulo-ocular reflex testing equipment, head-shaking test, and rotary chair test to check your balance. They may also use electrocochleography to check the signals in your inner ear and the auditory nerve.
What Is Ototoxicity Treatment?
The ideal ototoxicity treatment is to stop taking ototoxic medicines. This often helps reverse the symptoms. Your doctor may reduce the dose of the medicine or change your prescription.
If the medicine can’t be stopped or changed, the audiologist will help you manage hearing and balance problems through other treatments. They may also use listening therapy and lip-reading. The audiologist will regularly monitor your hearing and balance throughout the treatment period.
If you have serious inner ear damage you may need the following to manage your condition:
1. Amplification device. This device is a frequency modulation or FM system. It helps reduce background noise and improves hearing.
2. Hearing aids. These devices can be placed inside or behind the ear. They help you to hear well.
3. Cochlear implants. These are hearing devices that are surgically implanted into the scalp. A microphone behind the ear catches sound waves and sends them to the implanted device. It sends signals directly to your auditory nerve instead of passing them through the damaged inner ear. This allows you to hear.
4. Balance therapy. If you have balance problems, you will be prescribed balance therapy. It is also called vestibular rehabilitation. A physical therapist will help you with exercises to improve your balance, posture, and coordination. Physical therapy involves bending exercises and standing or walking with your eyes open and then closed.
Your doctor will recommend follow-up tests to check if your hearing and balance have improved. They may use questionnaires and other diagnostic tests to ensure recovery.
What Are the Complications of Ototoxicity?
If you have ototoxicity symptoms, it’s best to get diagnosed and start treatment without any delay. Ototoxicity can lead to long-term hearing loss and balance problems. Balance problems can increase your risk of falling and affect your daily activities.
In children, meanwhile, early diagnosis is crucial to prevent hearing, speech, and language problems.
If you notice symptoms while you are taking high doses of certain medicines, consult your doctor about potentially changing your prescription.
Prevention and Other Considerations
The best way to prevent ototoxicity is to avoid using ototoxic medications unless absolutely necessary. Additionally, if you come in contact with an environmental ototoxin, make sure you’re in a ventilated place. Open windows, turn on a fan, and stay away from the chemical as much as possible.
Monitor your hearing and balance regularly if you suspect that you are dealing with ototoxicity. If you're on an ototoxic medication and are concerned about your health, contact your doctor for more information.