Phantom Rising

To some, it is a constant buzzing in their ears; for others, it is a sort of whistling, humming or even the usually calming sounds made by crickets.

Kim Scott, executive director of the Sudbury, Ontario branch of the Canadian Hard of Hearing Association, was born hard of hearing and has been living with tinnitus for as long as she can remember. “I have moderate to severe tinnitus depending on the day,” Scott says.

And depending on the ear, what she hears is markedly different. For one ear, the predominant sound (or sensation) is “a screeching wind in a tunnel, like a subway in Toronto,” while for the other, it is “more like a French horn,” she laughs.

Scott’s sense of humour may have helped her to adapt to the phantom ringing, whistling or humming that is tinnitus, but the condition is no laughing matter. The debilitating hearing impairment is a crippling experience for about 360,000 Canadians, with approximately 150,000 finding the quality of their lives seriously compromised, notes estimates by the Tinnitus Association of Canada in Toronto.

Whether tinnitus is linked to aging, injury or work conditions, it can wreak havoc on concentration and mental fitness, neither of which is good for worker health, safety or performance. “If they are getting inadequate amounts of sleep,” says Scott, “it can definitely affect workplace performance.” 

OLD GETS NEW

Tinnitus is receiving more notice of late. And several studies by universities north and south of the border are providing new insights to this old problem.

A team made up of university researchers from Canada and the United States reports that the tinnitus “sound” – described by most patients as a constant, high-pitched ring or hiss – is generated by neurons firing in the brain, not the ear. “Hearing loss associated with noise exposure or the aging process sets the occasion for the large majority of cases of tinnitus,” says Larry Roberts, Ph.D., a professor in the Department of Psychology, Neuroscience and Behaviour at McMaster University in Hamilton, Ontario. 

“Tinnitus itself is brought on by changes in the brain that take place when hearing loss occurs,” says Dr. Roberts, the study’s lead investigator for the McMaster group.

He explains that neurons in the brain are designed to receive input from the ear. When hearing loss causes the brain, in effect, to disconnect from the ear, neurons in the brain’s auditory regions start to “talk” among themselves to compensate for the loss of auditory input. This communication, or neural synchrony, generates the tinnitus sensation, he says.

As neurons communicate with one another, their connections are strengthened in a process called neural plasticity. Understanding the changes in the brain is “very helpful” in devising treatments that can reverse neural plasticity and mitigate tinnitus, Dr. Roberts suggests.

Professor Josef Rauschecker, Ph.D., lead investigator for a study out of Georgetown University Medical Centre in Washington, D.C., says the team found “very prominent changes in extra-auditory structures” or the limbic part of the brain in tinnitus patients.

Using functional magnetic resonance imaging, half of the 22 volunteers tested were diagnosed with chronic tinnitus. Moderate hyperactivity was present in the primary and posterior auditory cortices of tinnitus patients.

“We believe that a dysregulation of the limbic and auditory networks may be at the heart of chronic tinnitus,” says Dr. Rauschecker. “Hair cells in your inner ear die because of excessive noise, but the cells in the brain are still there and are behaving as if you hear that sound,” he explains.

NOISE AND MORE

While the majority of people with tinnitus do have some form of hearing loss, “it is not a one-to-one correspondence,” Dr. Rauschecker says. Aging, head injury, poor blood circulation or disruption of blood flow can trigger tinnitus.

“The ears are very sensitive organs. There’s blood flow to the cochlear and the poorer that blood flow, the more likely that person will get tinnitus,” notes Terence Miranda, doctor of audiology for Resonance Hearing Clinic in Duncan, British Columbia.

Like hearing loss, tinnitus typically starts off as a mild ringing and gradually increases in intensity. Those with the condition wait on average five to seven years before seeking medical attention, says Dr. Miranda.

“Anybody who is exposed to loud noises is at risk,” he suggests, including those who work in construction, transportation (such as in airports and road works), the resources sector (think logging and mining), or as musicians.

For example, tinnitus is a major cause of disability in soldiers returning from Afghanistan and Iraq, notes a statement from McMaster University. “The common denominator for all these is loud noise exposure,” Dr. Rauschecker says.

Duration of exposure is also an issue. Scott points to the forestry industry in and around Sudbury. “Because of the nature of our primary industries up here, people are exposed to excessive amounts of noise. As a result of that, the rate of hearing loss up here is almost 50 per cent higher for them than it is for the rest of the province as a whole,” she says.

However, determining whether or not tinnitus is the result of occupational exposures certainly can be tricky. There is no test to identify the exact cause of tinnitus, although work-related conditions may point the way.

Take an employee who works in an environment where the sound level exceeds 90 decibels for a long period of time, notes Dr. Roberts. “If a person in this situation develops tinnitus, the likelihood that tinnitus is related to their occupational exposure is pretty substantial.”

MATTER OF RANGE

While tinnitus sufferers usually experience hearing loss in the high-frequency spectrum, many retain fairly normal conversational hearing, which registers in the low-frequency range. So what might be the work-related ramifications?

“It all boils down to whether the sounds you need to hear are in the frequency region of the tinnitus,” suggests Dr. Roberts. “If you are a railroad engineer and you can’t hear the whistle,” either because of hearing loss or the frequency of the whistle, “that might be risky,” he says.

Dr. Miranda agrees, citing a worker with tinnitus who may not hear the high-frequency beeping that accompanies a reversing truck.

The severity of tinnitus must also be considered. Since the humming associated with chronic tinnitus is usually more intense at night, this can increase the likelihood of sleep deprivation and greater stress.

Sleep challenges also threaten to set in motion a series of involuntary bodily responses that include elevated blood pressure and muscle contraction – all of which can aggravate tinnitus and compromise work-related safety, says Scott.

“If you are getting caught in a cycle,” she says, it becomes important to recognize that and to identify the steps needed to break out of that cycle.

“The emotional consequences of having tinnitus are very disruptive in the workplace,” Dr. Roberts says. “It certainly is a cause for anxiety, depression and a lot of emotional distress,” he reports.

But all is not lost. The hard knock of emotional consequences tends to subside as a person becomes more familiar with the condition and develops coping strategies, he says.

EXTEND A HAND

Tinnitus has no cure, but there are certainly coping strategies. One option is sound or masking therapy, which involves getting a tinnitus patient to listen to sounds engineered to contain the frequency or pitches within his or her range to help reverse the neural plasticity, Dr. Roberts explains.

Another approach calls for injecting magnetic pulses into the brain via a procedure known as transcranial magnetic stimulation, which disrupts synchronous activity.

And a recent study out of the University of Texas in Dallas offers
hope that a new treatment may be on the horizon. Researchers reported that pairing sounds with stimulation of the vagus nerve – a cranial nerve with branches to, among other places, the larynx, throat, windpipe, lungs, heart and most of the digestive system – eliminated tinnitus in rats.

By pairing tones with brief pulses of vagus nerve stimulation, the process retrains the brain to ignore the nerve signals that stimulate the ringing, notes a university statement.

“This minimally invasive method of generating neural plasticity allows us to precisely manipulate brain circuits which cannot be achieved with drugs,” Dr. Navzer Engineer, lead author of the study from Texas, notes in the statement.

Precision is provided “by rewiring damaged circuits and reversing the abnormal activity that generates the phantom sound,” Dr. Engineer says. A clinical trial in humans was scheduled to begin in early 2011.

As understanding of tinnitus gains ground through new research, sufferers are given more hope that the ringing in their heads may some day be silenced.  

Jean Lian is assistant editor of OHS CANADA.

Sidebar:

KEEP IT DOWN

The goal should always be to reduce workplace noise, something that Josef Rauschecker, Ph.D., a professor at Georgetown University Medical Centre in Washington, D.C., says both businesses and governments need to do more about. While noise remains too high, protective gear is a must – as is worker compliance.

Conducting an audiological assessment every couple of years is a good practice, suggests Kim Scott, executive director of the Sudbury, Ontario branch of the Canadian Hard of Hearing Association. Scott says that if the assessment indicates hearing loss, medical intervention can then be explored; if there is no hearing loss, the assessment helps to rule out possible underlying health concerns.

Scott recommends that people suffering from tinnitus read up on the condition. “A lot of people find if they learn what their triggers are, what can aggravate it and make it louder, they can learn to take steps to minimize that,” she says.

Tinnitus patients should avoid extreme silence as the brain generates the buzzing sensation to compensate for the lack of auditory stimulus, notes information from the Tinnitus and Hyperacusis Centre in the United Kingdom. Consider always having a pleasant, non-intrusive background sound such as a running fan, an open window or a device that plays white noise or sounds of nature.

For her part, Scott says she finds that wearing a hearing aid is tremendously helpful. “As soon as you put them on, your tinnitus seems lower,” she advises.

Maintaining good health, both mental and physical, can also be supportive. “Tinnitus does get worse when you are under a lot of emotional strain,” says Larry Roberts, Ph.D., a professor in the Department of Psychology, Neuroscience and Behaviour at McMaster University in Hamilton, Ontario.

Employers can offer a supportive work environment by being sensitive to employees with tinnitus and acknowledging that phantom ring is not just a psychological issue, but also a physical one, Scott recommends.