Millions of US citizens hear ringing in their ears, a condition called tinnitus. According to new research an experimental device could help quiet the phantom sounds by targeting unruly nerve activity in the brain.
In a new study in Science Translational Medicine, a team from the University of Michigan reported the results of the first animal tests and clinical trial of the approach, which included data from 20 human tinnitus patients.
On the basis of years of scientific research into the root causes of the condition, the device uses precisely-timed sounds coupled with weak electrical pulses that activate touch-sensitive nerves, both aimed at restoring normal activity to damaged nerve cells.
Human participants reported that the loudness of phantom sounds decreased following four weeks of daily use of the device. Also their tinnitus-related quality of life improved, but a sham "treatment" which only used sounds did not produce such effects.
Results from studies with guinea pigs and a double-blind human study funded by the Coulter Foundation validate years of preclinical research funded by the National Institutes of Health, including previous tests in guinea pigs.
"The brain, and specifically the region of the brainstem called the dorsal cochlear nucleus, is the root of tinnitus," said Susan Shore, the U-M Medical School professor who leads the research team.
"When the main neurons in this region, called fusiform cells, become hyperactive and synchronize with one another, the phantom signal is transmitted into other centers where perception occurs.
"If we can stop these signals, we can stop tinnitus. That is what our approach attempts to do, and we're encouraged by these initial parallel results in animals and humans."
To do so, the researchers designed a gadget that perfectly times sound and skin stimulation to target the nerve activity that causes the signal.
''The device plays a sound into the ears, alternating it with precisely timed, mild electrical pulses delivered to the cheek or neck. This sets off a process called stimulus timing-dependent plasticity, or STDP. The approach aims to reset the activity of fusiform cells,'' the authors wrote.
The invention was then tested on 20 humans, who used it for a half an hour every day for one month. After they analysed the results the researchers found that two of the participants were cured completely, and 11 reported reduced noise and pitch levels.