Scientists unravel the complex brain mechanisms responsible for tinnitus

For the first time, researchers have recorded directly from the brain of someone with the condition to find the brain networks linked to causing the debilitating problem in order to gain a better understanding of the issue.

Dr William Sedley, from Newcastle University’s Institute of Neuroscience, co-led the international research with Dr Phillip Gander, from the University of Iowa in America. Their research contrasted brain activity during periods when tinnitus was relatively stronger and weaker.

The research was only possible because the 50-year-old man they studied required invasive electrode monitoring for epilepsy. He also happened to have a typical pattern of tinnitus, including ringing in both ears, in association with hearing loss.

Findings of the research, which are today (April 23) published in the Cell Press journal Current Biology, shed new light on the mechanisms of tinnitus and it is hoped that this will eventually lead to better treatments for patients. 

The researchers found the expected tinnitus-linked brain activity, but they report that the unusual activity extended far beyond circumscribed auditory cortical regions to encompass almost all of the auditory cortex, along with other parts of the brain. 

Dr Sedley said: “This is a big step forward in our understanding of tinnitus, as it is the first time we have been able to clearly associate the patient’s own subjective experience of tinnitus with direct and precise measurements of brain activity.

“Perhaps the most remarkable finding was that activity directly linked to tinnitus was very extensive, and spanned a large proportion of the part of the brain we measured from. In contrast, the brain responses to a sound we played that mimicked the tinnitus were localised to a tiny area.

“We hope that the extra amount of knowledge we have gained will indirectly help us to develop more treatments for patients in the future. For Newcastle University to collaborate with scientists in America reflects the great work that’s going on into this common condition.”

Approximately one in five people experience tinnitus, the perception of a sound – often described as ringing – that isn’t really there. In the UK it is estimated that around six million people have mild tinnitus, with around 600,000 experiencing it to the severity where their quality of life is affected.

The study may help to inform treatments such as neurofeedback, where patients learn to control their ‘brainwaves’, or electromagnetic brain stimulation, according to the researchers. A better understanding of the brain patterns associated with tinnitus may also help point towards new pharmacological approaches to treatment.

Dr Sedley, who also works for Newcastle Hospitals NHS Foundation Trust’s neurology department, added: “We now know that tinnitus is represented very differently in the brain to normal sounds, even ones that sound the same, and therefore these cannot necessarily be used as the basis for understanding tinnitus or targeting treatment.”

Studies on the patient took place in the University of Iowa’s Institute for Clinical and Translational Science, where patients requiring epilepsy surgery are often studied for up to two weeks with electrodes implanted in their brains, in order to locate the part of the brain responsible for the epilepsy so that it can be removed.

Dr Gander said: “It is such a rarity that a person requiring invasive electrode monitoring for epilepsy also has tinnitus that we aim to study every such person if they are willing.

“The sheer amount of the brain across which the tinnitus network is present suggests that tinnitus may not simply ‘fill in’ the ‘gap’ left by hearing damage, but also actively infiltrates beyond this into wider brain systems.”

The research was funded by the Wellcome Trust and Medical Research Council in the UK, and the National Institutes of Health in the USA. At present the research is based on a single patient, but over time the researchers are hopeful of being able to study more patients with tinnitus in a similar way.

Dr Ralph Holme, Action on Hearing Loss Head of Biomedical Research, said: “Tinnitus is a debilitating condition, for which there is currently no cure. 

“We welcome investment and research into tinnitus as the mechanisms behind it are still not fully understood and more progress is needed to improve the chances of effective treatments in the future.”

Case study

Father-of-two Lindsay Waddell has suffered from tinnitus for 10 years and welcomes the new research.

The head gamekeeper has spent most of his life working on farms and believes the constant noise of heavy machinery has contributed towards his condition.      

Mr Waddell, 64, from Middleton-in-Teesdale, County Durham, said: “My tinnitus has got worse over the years and it sounds like a constant hissing in my ears. Since I was a teenager I’ve been surrounded by the loud noise of farm machinery and I think this has damaged my hearing.

“I’m delighted that this research has been carried out as it’s a great step forward in understanding tinnitus, which will hopefully help lead to the development of new treatments in the future for those suffering the condition.

“Newcastle University is often leading the way with research and this is another example of that.”

 Photo caption: Dr William Sedley, from Newcastle University’s Institute of Neuroscience




published on: 23rd April 2015


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