The scientists at the University of Düsseldorf were researching the mechanism behind one of the symptoms of Tourette’s, known as “echophenomena” – involuntarily repeating the words or movements of others.
They managed to induce this reaction in healthy human subjects by stimulating the supplementary motor area (SMA) of the brain, which controls movement. This could lead to non-drug therapy to reduce tics and repetitions in Tourette’s patients.
Tourette’s sufferers often carry out quick, involuntary movements – common tics include shrugging shoulders, nodding, or suddenly lifting their arms. They also often copy the movements of people they happen to be looking at.
Between 300,000 and 500,000 adults are said to have the syndrome in Germany, according to estimates from the German neurology society (DGN).
“The causes and mechanisms of this echoing have hardly been studied,” the researchers wrote in the scientific journal Cortex. In particular, it had not been clear before whether the different types of tics – movement and noises – originated from the same part of the brain.
“We now know more about Tourette’s and how it works,” Jennifer Finis of Düsseldorf University, one of the scientists behind the experiment, told The Local. “It’s a good starting point.”
At the moment, Tourette’s is generally treated with neuroleptic medication. “But a lot of people don’t like to take them, because they have a lot side-effects – they get very tired – and for some people they don’t even work,” said Finis.
The researchers carried out “repetitive transcranial magnetic stimulation” (rTMS) on 30 healthy volunteers. This involved attaching a probe to their heads, sending out strong magnetic pulses. Depending on the length of the pulses, these either stimulated or suppressed activity in the SMA.
The researchers attempted to stimulate the reaction in 15 of the subjects, and suppress it in the other 15. Before and after each treatment, the subjects were shown videos of people carrying out spontaneous movements – such as raising an eyebrow, moving the mouth or the eyes.
The subjects whose brains had been stimulated by the rTMS imitated the movements three times as much as those whose SMA activity had been suppressed.
The scientists now want to test whether rTMS can be used to reduce tics and echophenomena in Tourette’s sufferers. “So the logical consequence now would be to try the rTMS on the SMA on Tourette’s patients to see if that works,” said Finis.
But she stressed that scientists were unsure if successful rTMS treatment would cure the syndrome itself, or just its symptoms.
“It’s very complicated with Tourette’s,” she said. “We do know now that the SMA is overactive in Tourette’s patients, but we don’t know why. We don’t know if this is the cause or if it’s just a consequence of something else which is wrong.”