We live in a world awash with sound. Vibrations in the air travel through the ears to the brain via electrical impulses. And the brain, in turn, interprets Beethoven’s Fifth Symphony, jarring car horns, and loving words from different vibrations.
Tinnitus, a maddening hearing disorder commonly characterized by a ringing in one or both ears, disrupts or even drowns out that background music of life. It blares with rings, clicks, or roars, even in the absence of an external sound.
For the majority of patients with tinnitus, the brain imagines the noise, which varies wildly from person to person in pitch, tone, and intensity. Sometimes hearing loss accompanies tinnitus, while for others, their hearing remains normal.
Tinnitus ranked first last year among service-related disabilities for veterans returning from Iraq and Afghanistan, and about 50 million Americans - civilians and vets alike - experience tinnitus at some point in their lives, according to the American Tinnitus Association.
It may be a symptom of underlying medical conditions including kidney disease, but it is a real illness for its sufferers, especially for chronic tinnitus patients who have no respite from the incessant noise. Treatment for those with chronic and severe tinnitus is a must to prevent compounding the condition with depression or other psychological disorders.
Dr. Alan Micco, an associate professor of otolaryngology (ear, nose and throat) and neurological surgery at Northwestern University, tackles tinnitus in his research and medical practice. Medill Reports spoke with Micco about what causes tinnitus, the challenges that remain in its treatment, and his personal experience with the condition.
Georgetown University Medical Center recently called for more research on the central nervous system’s role in tinnitus. What are your thoughts on a brain-centric approach to identify possible cures?
Brain research is hot right now, but we’ve known for a while that tinnitus is a central nervous system problem. Over 20 years ago, researchers found that people who used anti-anxiety and anti-depressant medications, such as amitriptyline and aprazolam, showed improvement in their tinnitus symptoms. This may have been because of the medications’ effects on the brain, possibly due to a sedative effect that decreases perception. Stress and anxiety can make you fixate on the tinnitus.
Have physical changes in the brain been documented in tinnitus patients?
Yes. PET scans, [imaging tests that use radioactive materials to display tissues and organs], show that patients with tinnitus have increased levels of activity in their left temporal lobe. The auditory cortex, [which processes sound], is in the left temporal lobe. Some drastic measures for tinnitus treatment in the past included implantable electrodes on the brain to stimulate the brain in this region. But this was obviously for people at suicide’s door.
What is the current understanding in the medical community of why tinnitus occurs?
The classic model thought tinnitus was caused by some sort of damage to the inner ear, like an acoustic trauma. Acoustic traumas can be caused by obvious events like a firecracker going off. But the second most common contributor can be medications. Anti-inflammatories such as aspirin and ibuprofen and certain chemotherapy and cardiac drugs may [contribute to] tinnitus. These medications can be toxic to the hair cells [that are critical to hearing] in the inner ear. But we’ve also known that there’s a central nervous system component. In other words, it’s a problem with the brain.
A brain problem? How so?
Tinnitus is a phantom noise. Instead of hearing something generated by the outside environment, you’re hearing something that’s not there. The brain gets stuck in a loop and fixates on the noise.
What’s the relationship between hearing and perception?
The brain is very plastic. The brain can selectively learn to hear and ignore sounds. Basically, we intake more sound waves through our ears than what actually registers in our brain.
So if you treat the brain by reversing the brain’s fixation on the phantom noise, will you be able to treat tinnitus?
If you can get the brain to focus in on another sound, it can potentially resolve tinnitus. So yes, that’s what all these therapies, such as tinnitus retraining therapy, are trying to do. Going back to the electrical stimulation, all they were doing was sending an erratic auditory signal to the auditory cortex. Regardless of where the electric stimulation is coming from, if you directly stimulate the brain stem with an electrical signal, you’ll hear something, even if you didn’t stimulate the ear. The brain can potentially hear it.
What is tinnitus retraining therapy?
Certain companies, such as Neuromonics, [located in Bethlehem, PA.], make a device that plays classical music with white noise in the background. The audiologist will present frequency tones at a comfortable level for the patient until he hits the pitch of the tinnitus. Then basically the audiologist will send that information to one of these companies, who will create these mp3 players with music and the white noise that matches the pitch of the particular tinnitus...and gradually, through repeated exposure, the sound becomes less significant.
But there’s no causal relationship between hearing loss and tinnitus, is there?
No. Just because you having hearing loss doesn’t mean you’ll develop tinnitus, and vice versa. You can have normal hearing and not have tinnitus. But it’s more common for tinnitus to accompany hearing loss, due to two things. If you have hearing loss, you have hair cell damage in the inner ear. Or you may have neural damage. So if you have either of those, you are bound to get an abnormal signaling to the brain. Whether you have cochlear damage or an acoustic tumor pressing on your nerve, all along the whole auditory chain, starting with your ear, there’s encoding going on. So if a person has something pressing on their brain stem or a nerve, they can get tinnitus. As long as there is something damaging or stressing the system, you can develop tinnitus.
How do the hair cells function?
Hair cells [in the inner ear] act like piano strings and are calibrated to hear certain pitches. When they are damaged, the vibration tends to localize, which causes electrical overload as the sound signal is transmitted to the brain. Basically, the auditory system tries to compensate for a hearing loss in a certain area of the cochlea. The edges of the damage become hypersensitive, and typically what happens is that they overcompensate. So that’s why a person with hearing loss may perceive a sound as really harsh, although it’s not. The cells can’t regenerate and they can’t re-grow themselves. Not in humans. Not yet, anyway. We know some animals, like birds, do it.
Although tinnitus is a phantom noise, it manifests as a real “disease” for sufferers, right?
Yes, although essentially it’s really a symptom and not a disease. Tinnitus can be a harbinger of other diseases, such as inner ear malfunction. It can also be a warning sign for [impending] hearing loss. There’s a lot of misinformation out there and [it can be frustrating because] insurance doesn’t cover hearing aids and treatments such as tinnitus retraining therapies. But when patients come into my office complaining about their tinnitus and say that I don’t understand, I say that, actually, I do. I’ve had tinnitus since I was a young boy. I can hear it right now if I pay attention to it.