A fascinating publication from the University of Nottingham describes a non-invasive method that may reduce tics. The idea is that rhythmic input to a brain region can entrain that region to fire in synchrony with the input, and some rhythmic firing patterns seem to inhibit movement. The stimulation was delivered by generating a small electrical current to the skin over a nerve in the wrist (the median nerve). The current is dialed down to just barely enough to make the thumb twitch.
The authors tested this new idea in two ways. First, they showed that brain activity in an area of the brain corresponding to sensation and movement could be synchronized with the electrical pulses at the wrist. A control condition with the pulses delivered differently did not produce the same effect.
Second, 19 volunteers with TS engaged in a 4-minute-long study in which 2 of the minutes included median nerve stimulation (MNS) and 2 minutes did not. The order of stimulation vs. no stimulation varied across participants. Six of the 19 people found the stimulation uncomfortable. The participants were video recorded during the 4 minutes, and a tic doctor who didn’t know when the stimulation was on or off counted tics and rated their severity for each minute of the 4 minutes. Different people had different results, but on average, tic frequency and severity decreased (by about 30%; see Figure 5 in the paper referenced below). A few participants reported dramatic benefit during stimulation (see video S1 in the paper referenced below). Their experience was shared in the news, which of course has generated substantial interest from the public.
The Nottingham experiment is very clever, and provides a potential new treatment. However, important questions remain. Can the improvement be made to last more than a few minutes? How many people improve with MNS? Can we predict who will benefit and who won’t? Does the stimulation have to be delivered they way they did it to produce clinical benefit? Can the stimulation be provided, say, for 5 seconds every minute, or does it need to be continuous? We need to know some of these answers before we know how useful MNS may be in real life.
I have been working with the researchers from Nottingham, who are continuing with this line of research, and we are starting a follow-up study here at Washington University.
It’s worth remembering that MNS is far from the only option for treatment. Several effective treatments for tics are already available, and we are also testing new medications and behavior therapies.
UPDATE June, 2021: We are enrolling! Click here to find out how to volunteer.
Morera Maiquez B et al.: Entraining Movement-Related Brain Oscillations to Suppress Tics in Tourette Syndrome. Current Biology 2020; DOI 10.1016/j.cub.2020.04.044.