Somatosensory-motor bodily representation cortical thinning in Tourette: effects of tic severity, age and gender.
BACKGROUND
Tourette syndrome (TS) implicates the disinhibition of the cortico-striatal-thalamic-cortical circuitry (CSTC). Previous studies used a volumetric approach to investigate this circuitry with inconsistent findings. Cortical thickness may represent a more reliable measure than volume due to the low variability in the cytoarchitectural structure of the grey matter.


METHODS
66 magnetic resonance imaging scans were acquired from 34 TS subjects (age range 10-25, mean 17.19+/-4.1) and 32 normal controls (NC) (age range 10-20, mean 16.33+/-3.56). Brain morphology was assessed using the fully automated CIVET pipeline at the Montreal Neurological Institute.


RESULTS
We report (1) significant cortical thinning in the fronto-parietal and somatosensory-motor cortices in TS relative to NC (p<.05); (2) TS boys showed thinner cortex relative to TS girls in the fronto-parietal cortical regions (p<.05); (3) significant decrease in the fronto-parietal mean cortical thickness in TS subjects with age relative to NC and in the pre-central cortex in TS boys relative to TS girls; (4) significant negative correlations between tic severity and the somatosensory-motor cortical thickness.


CONCLUSIONS
TS revealed important thinning in brain regions particularly involved in the somatosensory/motor bodily representations which may play an important role in tics. Our findings are in agreement with Leckman et al. (1991) hypothesis stating that facial tics would be associated with dysfunction in an orofacial subset of the motor circuit, eye blinking with the occulo-motor circuit, whereas lack of inhibition to a dysfunction in the prefrontal cortex. Gender and age differences may reflect differential etiological factors, which have significant clinical relevance in TS and should be considered in developing and using diagnostic and therapeutic interventions.
Fahim
Cherine
C
Department of Neurology and Neurosurgery, McGill University, 3081 University Street, Montréal, Quebec, Canada.
Yoon
Uicheul
U
Das
Samir
S
Lyttelton
Oliver
O
Chen
John
J
Arnaoutelis
Rozie
R
Rouleau
Guy
G
Sandor
Paul
P
Frey
Kirk
K
Brandner
Catherine
C
Evans
Alan C
AC
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001331:Automation; D002648:Child; D005260:Female; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000473:pathology*; D009929:Organ Size; D010296:Parietal Lobe / Q000473:pathology; D012720:Severity of Illness Index; D012737:Sex Factors; D013003:Somatosensory Cortex / Q000473:pathology*; D020323:Tics / Q000473:pathology; D005879:Tourette Syndrome / Q000473:pathology*; D055815:Young Adult