Tinnitus: the sound of silence

“The Sound of Silence” is not just a title of one of Simon and Garfunkel’s biggest 1960s hits, it’s also an ironic reality for millions of people who never experience real silence–because they hear noises all the time.

It’s a condition called tinnitus, and it’s one of the most common hearing afflictions around. The Tinnitus Association of Canada says more than 360,000 Canadians suffer from it “in an annoying form,” and the number of people who have it in a less-annoying form is undoubtedly far higher: estimates range from one in 10 to as high in one in five.

I’ve written about it before, about six years ago, but recently there’s been some new research that made me want to revisit it.

(Besides, tinnitus is always of interest to me, because I’m one of the people who has it: a constant, high-pitched ringing that I notice most when it’s very quiet, I’m very tired–or I decide to write a column about it, which draws my attention to it. Like right now. D’oh!)

One cause of tinnitus is exposure to loud noise: for example, in the U.S., nearly half of the soldiers returning from Iraq and Afghanistan who were exposed to explosions or gunfire suffer from it. That makes it the number-one war-related disability. (Presumably the numbers of First World War and Second World War troops suffering from it were astronomical, but it wasn’t tracked.)

In the past few years, several hearing organizations have issued warnings that the proliferation of portable music players like Apple’s iPod may be the precursor to an even greater epidemic of tinnitus down the road.

(What, you didn’t hear those warnings? Well, MAYBE IF YOU TOOK THE EARBUDS OUT OF YOUR EARS ONCE IN A…oh, never mind.)

Yet even though it’s common and poorly understood, relatively little research has been carried out on tinnitus and possible treatments.

One scientist trying to change that is Ernest Moore, an audiologist and cell biologist at Northwestern University, who is himself a tinnitus sufferer. (In his case, he figures, brought on by exposure to gunfire in the U.S. Army Reserves medical corps 20 years ago and possibly during opossum hunts as a kid in Tennessee.)

One of the challenges in researching tinnitus is developing an animal model. Researchers at John Hopkins university use rats that have been specially trained to stop drinking when they’re hearing things. But Moore has managed to produce the condition in a completely different animal, zebrafish, by exposing them to certain drugs. When they start swimming erratically, he examines their ear cells, and finds increased electrical activity.

He then attempts to block the effect with other drugs–and he’s had some success. Now he’s beginning to meet with doctors to discuss launching a clinical trial to test those drugs in human.

Some of the those drugs are already on the market for other uses, which could shorten the approval process.

Moore isn’t the only one working on the problem, of course. The aforementioned John Hopkins researchers have established, using their trained rats, that much of the problem originates in the brain, not in the ears.

When the brain’s auditory cortex receives diminished neural signals from the cochlea, the hearing organ in the ear, it “turns up the volume.” That means weak neural signals that arrive in the cochlea from other locations are amplified and interpreted by the brain as sound. (In another study, University of Michigan researchers have recently established that one source of the increased, tinnitus-producing signals are touch-sensitive nerves in the face and neck.)

In a newly funded five-year project, the John Hopkins researchers will be trying to identify precisely what aberrant pattern of neural activity in the auditory cortex is associated with the onset of tinnitus, monitoring over-all brain activity in tinnitus sufferers, and experimenting with the compounds that might be able to suppress the condition.

More research is likely in the offing: the Department of Defense’s 2008 Appropriations Bill in the U.S. includes $50 million for new research funding for tinnitus related to service in the armed forces.

Here’s hoping it pays off, and the true “sound of silence” will return to millions of people.

UPDATE (June 12/08): The following letter sent to the Red Deer Advocate after my column appeared there makes some important points, and is reprinted with the author’s permission:

Regarding the “Science” column in the Red Deer Life of Sunday June 1, 2008 [“Will that noise ever stop? By Edward Willett], I would like to thank the columnist for writing about tinnitus (ringing in the ears) for public consumption. Much of the content of the article is correct and accurate. However, in health care, perhaps the most dangerous errors are errors of omission. The columnist states that tinnitus is caused by exposure to loud noise. This is true for many people, particularly those that live and work in careers where they are exposed to industrial noise for long periods of time. It is important to understand though, that noise is not the only cause of tinnitus as the author seems to state. Tinnitus can be caused by, and be an indicator of, many different auditory or medical conditions ranging from simple impaction of wax against the eardrum to less common, but more serious conditions such as tumours that press on the auditory nerve. It can also be caused by outside factors such as side effects or interactions of medications or even issues with blood pressure. In many people, the source of the tinnitus is idiopathic (no known cause).

The bottom line is, while there is currently no cure for tinnitus per se, there may be treatment for the underlying cause of it, if and when that can be determined. Anyone who experiences tinnitus should have a complete and thorough examination by a clinical audiologist, and if necessary, otolarynglogist (ear, nose and throat physician).

Dr. Andrew D. Towers, AuD
Clinical Audiologist
Past President of the Alberta College of Speech-Language Pathologists and Audiologists (ACSLPA)
President of the Alberta Association of Audiologists