Mimicking a neurotransmitter called GABA - which blocks nerve transmission - could be an effective treatment option for tics among people with Tourette syndrome, researchers find.
Study co-author Prof. Stephen Jackson, of the School of Psychology at The University of Nottingham, and colleagues publish their findings in the journal Trends in Cognitive Sciences.
Tourette syndrome (TS) is a nervous system disorder estimated to affect 1 in 360 children in the US ages 6-17. The condition is more common in boys, with boys three to five times more likely to be diagnosed with TS than girls.
Tics are the main symptom of TS, normally developing between the ages of 5-10. There are two types of tics: motor and vocal. Motor tics involve involuntary body movements, such as blinking or arm jerking. Vocal tics involve involuntary sounds made with the voice, such as humming or shouting words or phrases.
In most cases of TS, the occurrence of tics reduces by early adulthood, and the majority of children can suppress them. However, some people with the disorder can experience a worsening of tics as they get older.
There is currently no cure for TS, though there are treatments that can help manage the condition. Comprehensive Behavioral Intervention for Tics (CBIT) and medications such as neuroleptics are the most common forms of treatment for TS.
But Prof. Jackson and colleagues believe a new form of treatment could be in the cards for people with TS, involving a brain chemical called Gamma Aminobutyric acid (GABA).
Mimicking increased GABA levels in the brain may help treat TS
Previous research has suggested that TS may be associated with changes in levels of GABA in the brain - an amino acid that blocks nerve transmission in the central nervous system, including areas of the brain that control movement.
- It is unclear exactly what causes TS, but researchers believe it is an inherited condition
- TS often develops alongside other conditions, such as attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD)
- While TS is often linked to involuntary shouting of swear words - called coprolalia - this is a rare symptom.
For example, studies involving brain scans of people with TS have shown that GABA levels are reduced by up to 50%.
Based on such findings, researchers believe reduced GABA levels may lead to overexcitement of nerve cells in people with TS, which causes tics.
According to Prof. Jackson and colleagues, one long-held belief is that young individuals with TS can control their tics by making a deliberate, ongoing effort to suppress them, which leads to a "re-wiring" within the brain's neural pathways.
However, the team found that brain changes during adolescence lead to an increase in GABA production, which may explain why young individuals with TS have better control over their tics.
As such, the researchers believe that mimicking the way in which GABA blocks nerve transmission in brain areas responsible for motor function may offer a promising treatment strategy for people with TS who are unable to manage their tics.
Commenting on their study, Prof. Jackson says:
"The finding that individuals with Tourette syndrome exhibit increased GABA in brain areas linked to the planning and selection of movements offers a more parsimonious account for how tics might be controlled in Tourette syndrome. Namely that motor excitability is reduced locally within brain motor areas through the operation of GABA-mediated 'tonic inhibition.'
This finding needs to be further replicated but if it proves to be a robust finding it may have important implications for therapies for neurodevelopmental disorders."