What Tourette Syndrome does to the brain

Nikolai is a perfectly normal, intelligent young man. But sometimes something goes wrong in his brain – and out of the blue his head starts twitching, his eyes start blinking and he starts grimacing. Sometimes Nikolai even can’t help but scream – obscene words burst out of his mouth without his control. It is as if something is forcing him to act this way.

No matter how hard he tries, Nikolai cannot control his tics. They seem to come and go at random. In medicine, this type of neuropsychiatric disorder is called Tourette syndrome. It is named after the French neurologist Dr. Georges Gilles de la Tourette, who first described it in 1825.

What it feels like to have Tourette Syndrome

Nicolai himself describes his condition as follows: “Imagine there is something inside you. It builds up pressure in your body, and it gets stronger and stronger, until at some point you have to release it – by screaming, by shaking, it’s like a hiccup. You notice it’s coming, you can suppress it for a moment, but then it just has to come out.”

Tourette Syndrome is a neuropsychiatric disorder characterized by motor and vocal tics. Many – but not all – people with Tourette Syndrome also suffer from compulsive behaviors. Holding a drinking glass gives Nikolai the urge to crush it with his hand. He cannot resist this compulsion, despite the risk of hurting himself.

These tics and obsessions vary from person to person. They usually occur at irregular intervals. Their frequency and intensity may change periodically. Sometimes they disappear for a short time and then suddenly reappear. Only about one percent of people with Tourette’s also have what is called coprolalia: the compulsion to utter obscene words.

Tourette’s syndrome usually first appears around the age of seven, increases during puberty, and decreases with age. One in a thousand people is affected by this neurological disorder. It is three times more common in men than in women. The reason is still unknown.

The Harvard Brain Bank

The Harvard Brain Bank is the world’s largest archive of human brains. Over four thousand are stored here for scientific purposes. But Tourette’s brains are very rare. With luck, the Brain Bank receives one a year.

To learn more about Tourette syndrome, scientists freeze the core of the brain, called the basal ganglia, in dry ice. The basal ganglia are the switching centers of the nervous system, comparable to telephone switchboards, and are responsible for motor function. Neurologists suspect that this is where the disease originates.

One by one, they scrape off thin slices, each 1/20th of a millimeter thick, from the frozen brain core to study the basal ganglia more closely. They place each slice in a special solution. This allows them to study which chemicals are present and in what concentrations.

The scientists are looking for chemicals that are neurotransmitters, which are necessary for communication between nerve cells. One neurotransmitter they are particularly interested in is dopamine. This chemical influences the way we act out our impulses. In the brains of Tourette’s patients, it appears to be released uncontrollably, most likely causing tics and involuntary movements.

In people without Tourette’s, dopamine is distributed evenly throughout the body. In people with Tourette’s, however, the concentration is extremely high in certain areas. If scientists can find out how, where and why this maldistribution is caused, they may be able to develop new therapies and medications with fewer side effects than those currently on the market.

Getting high for research

Fearing social rejection, some Tourette’s sufferers hide their symptoms by taking medication. But these so-called neuroleptics often have side effects. Nikolai has not yet found the right medication for him. So far, he prefers having tics to the side effects of medication.

In Germany, neurologists at the Hanover Medical School have been testing a new form of therapy. It is based on a familiar but still controversial drug: the cannabis plant. Tourette’s patients reported having fewer or no tics after using cannabis.

Marijuana is illegal in many countries. However, its active ingredient, THC (tetrahydrocannabinol), is legal and available in tablet or drop form. How THC is able to suppress Tourette’s syndrome is not entirely clear. It is possible that it affects specific nerve receptors in the brain.

Smoking weed for science

To find out more about how THC affects the brain, the Hannover Medical School conducted a placebo-controlled study with 24 test subjects in 2016, led by physician Dr. Kirsten Müller-Vahl. Nikolai was one of the participants in this cannabis study.

The researchers injected Nikolai with a radioactive liquid so they could take a look inside his brain. Using a procedure called single-photon emission computed tomography (SPECT), the researchers were able to determine how many cannabis receptors there were in Nikolai’s brain and where they were located.

It has been known for about ten years that there are receptors, also called binding sites, for cannabis and cannabis drugs in the brain. Initially, tests were performed on dead bodies and animals. The Hanover Medical School was the first in the world to develop and perform a method on living humans that makes it possible to visualize these binding sites.

Over the next few years, the experts at the Hanover Medical School plan to use this technology to examine more people and patients in order to further investigate the significance of this mechanism and whether there are specific diseases in which this system is disrupted.