The procedure, called deep brain stimulation ( DBS ), improved tic severity by nearly half in 171 patients with uncontrolled Tourette symptoms at 31 hospitals in 10 countries. Senior researcher Dr. Michael Okun, said, "To get that much improvement in these symptoms is difficult when using medication or behavioral therapy ."

With DBS, brain surgeons run thin electric leads to specific regions of the basal ganglia, a cluster of nerves in the brain related to motor control and behavior. Doctors then apply electricity to the brain circuits they have most closely linked to Tourette, to try to control the patient's tics .

However, the procedure still needs more work. More than a third of patients experienced adverse events, most often slurred speech or a pins-and-needles sensation. These side effects occur when electricity meant for one brain circuit unintentionally spreads to other nearby nerves, Okun explained.

"The circuits we want to drive or suppress are often next to circuits we do not want to disturb," Okun said. Future research will focus on improvements to electrical leads so they will more precisely deliver current to targeted brain circuits, he said.

Tourette patients are typically treated with medications and speech or behavioral therapy. An estimated 300,000 US children-about 1 out of every 160-are affected by Tourette, according to the Tourette Association of America.

Researchers wanted a better idea of ??whether DBS is effective in treating severe cases of uncontrolled Tourette , which can cause motor tics so strong that people end up hurting themselves. Unfortunately, even top institutions tend to use DBS on only one or two patients each year, Okun said.

This last study focused on the one-year follow-up results from 171 patients who underwent DBS implantation between 2012 and 2016, after other means of treating their Tourette had failed. Average tic severity in these patients improved by 45% within one year of DBS implantation, the data shows.

Diana Shineman said, "From this study, we could have some promise for those with severe Tourette syndrome that has not been responsive to other treatments." But more than 35% of patients treated with DBS developed adverse side effects. The most common were a pins-and-needles sensation and slurred speech. Two patients suffered from bleeding in their brain, and four patients developed an infection from their surgery.

The good news is that the pins-and-needles sensation called paresthesia  and the slurred speech ( dysarthria ) were reversible. "In almost all the cases, the effects solve by changing the program or turning the device off," Okun said.

To further reduce these side effects, future efforts will try to more precisely identify the nerves that cause Tourette symptoms, and then target them with better technology that more accurately monitors signals and delivers electrical impulses, Okun said.

Researchers are also developing to "smart" DBS that will only discharge current when needed, rather than maintain a continued electrical charge, Okun said. Okun said, "Now we are beginning to refine that with better leads and better technologies ."