Tourette's differences: MRI reveals

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  • Published: Nov 1, 2016
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Tourette's differences: MRI reveals

Sensory processing

Magnetic resonance imaging (MRI) has revealed that there are significant differences in parts of the brain between children with Tourette's syndrome and those without the neuropsychiatric disorder, according to data published by researchers at Washington University School of Medicine in St. Louis. Credit: Black et al/Mol Psychiatr

Magnetic resonance imaging (MRI) has revealed that there are significant differences in parts of the brain between children with Tourette's syndrome and those without the neuropsychiatric disorder, according to data published by researchers at Washington University School of Medicine in St. Louis. Details were published in the journal Molecular Psychiatry.

Tourette's syndrome is characterised by involuntary and repetitive movements, tics, blinking, coughing, throat clearing, sniffing, and facial movements as well as unwanted vocalizations. Estimates suggest that between and one and ten children in every thousand are affected. The tics can come and go and might be suppressed temporarily but are typically preceded by an unwanted urge or sensation in the affected muscles. Tourette's does not affect intelligence nor life expectancy. However, it is a worrying and troublesome condition for sufferers and their carers.

Kevin Black and his colleagues have now identified an important clue as to the origins of the disorder. "In this study, we found changes primarily in brain regions connected to sensation and sensory processing," Black explains. He points out that differences in those brain regions make sense because many people with Tourette's report that their tics happen in response to unusual sensations in the body. For instance, the feeling that a part of the body does not "seem right" might trigger an involuntary sigh, vocalization, cough or twitch.

Sensations

"Just as you or I might cough or sneeze due to a cold, a person with Tourette's frequently will have a feeling that something is wrong, and the tic makes it feel better," Black explains. "A young man who frequently clears his throat may report that doing so is a reaction to a tickle or some other unusual sensation in his throat. Or a young woman will move her shoulder when it feels strange, and the movement, which is a tic, will make the shoulder feel better." Although the notion that the tics are involuntary seems to conflict with this idea that the movements and vocalisations are done in response to a feeling in order to "correct" that feeling.

Black's team has carried out the largest study of its kind, carrying out MRI scans at four US sites to study the brains of 103 children with Tourette's syndrome and to compare those scans with the equivalent scan from an additional 103 children of the same age and gender but who do not have the disorder. The scans of the children with Tourette's syndrome showed that there is more grey matter in the thalamus, the hypothalamus and the mid-brain than in those children without the disorder. The grey matter is where the brain processes information. It is comprised mainly of neurons, glial cells and dendrites, as well as axons that extend from neurons to carry signals. The researchers also found that there was less white matter around the orbital prefrontal cortex, just above the eyes, and in the medial prefrontal cortex, also near the front, than in children without the condition.

Towards therapies

Given that the brain's white matter acts as the "wiring", transmitting signals to the grey matter. Less white matter could mean less efficient transmission of sensations, whereas extra grey matter could mean nerve cells are sending extra signals. It is not yet possible to know whether or not extra grey matter is transmitting information that somehow contributes to tics or whether it is the reduced amounts of white matter elsewhere in the brain that somehow influences the seemingly random movements and vocalizations. Regardless, the discovery of the differences will provide additional insights into the nature of Tourette's syndrome.

"This doesn't tell us what happened to make the brain look this way," Black adds. "Are there missing cells in certain places, or are the cells just smaller? And are these regions changing as the brain tries to resist tics? Or are the differences we observed contributing to problems with tics? We simply don’t know the answers yet." He adds that the researchers will next attempt to see whether their findings are corroborated by more MRI studies with patients and to begin to unravel how the brain regions identified as different are contributing to the symptoms of Tourette's syndrome. The ultimate goal being to develop new and more effective therapies.

Related Links

Mol Psychiatr, 2016, online: "Brain structure in pediatric Tourette syndrome"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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