Neuroimaging of tic disorders with co-existing attention-deficit/hyperactivity disorder.
BACKGROUND
Tourette syndrome (TS) and Attention-Deficit/Hyperactivity Disorder (ADHD) are common and debilitating neuropsychiatric illnesses that typically onset in the preschool years. Recently, both conditions have been subject to neuroimaging studies, with the aim of understanding their underlying neurobiological correlates.


OBJECTIVE
The relation of TS and ADHD is discussed against the background of findings from previous Magnetic Resonance Imaging (MRI) studies.


METHODS
We review the designs and major findings of previous studies that have examined TS with comorbid ADHD, and we briefly contrast these findings with those in ADHD without comorbid tic disorders.


RESULTS
The frequent comorbidity of TS and ADHD may reflect a common underlying neurobiological substrate, and studies confirm the hypothesized involvement of fronto-striatal circuits in both TS and ADHD. However, poor inhibitory control and volumetric reductions in fronto-striatal circuits appear to be core features of ADHD, whereas reduced volumes of the caudate nucleus, together with activation and hypertrophy of prefrontal regions that likely help to suppress tics, seem to be core features of TS.


CONCLUSIONS
The etiological relationship between TS and ADHD must be clarified further with cross-sectional and, if possible, longitudinal imaging studies that examine samples of substantial size, including subgroups with pure TS and ADHD, as well as with comorbid conditions.
Center for Child and Adolescent Mental Health, University of Bergen, Norway. kerstin.plessen@rbup.uib.no
Kerstin J
KJ
Plessen
Jason M
JM
Royal
Bradley S
BS
Peterson
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D002421:Caudate Nucleus / Q000473:pathology / Q000503:physiopathology; D002648:Child; D003337:Corpus Callosum / Q000473:pathology / Q000503:physiopathology; D003342:Corpus Striatum / Q000473:pathology / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009415:Nerve Net / Q000473:pathology / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D017397:Prefrontal Cortex / Q000473:pathology / Q000503:physiopathology; D012016:Reference Values; D005879:Tourette Syndrome / Q000150:complications / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid