Actualité en neuro-imagerie du Trouble Déficit d’Attention/Hyperactivité

Abstract

An increasing number of neuroimaging (in particular, magnetic resonance imaging [MRI]) studies has been published in the last two decades with the aim to elucidate the brain correlates of Attention-Deficit/Hyperactivity Disorder (ADHD). The amount of available evidence has allowed researchers to pool such body of studies in meta-analyses, which provide more reliable information than single and often underpowered studies. Meta-analytic evidence from structural MRI studies shows that, compared to non-ADHD controls, individuals with ADHD present with significant differences in the volume of fronto-parietal, striatal, thalamic and cerebellar regions, involved in inhibition, self-adjustment and goal-directed behaviors, functions typically impaired in ADHD. Converging evidence from diffusion tensor imaging studies also shows ADHD-related white matter alterations in fronto-striatal-cerebellar circuits as well as in parieto-temporal-occipital regions. Evidence from structural studies has been complemented by task-based functional MRI studies pointing to dysfunctions in the same brain regions. The relatively recent introduction of resting-state MRI has allowed the detection of complex patterns of dysfunctional interactions, at rest, among several brain networks, including the default and task-positive networks, in individuals with ADHD. To date, most of the neuroimaging literature in ADHD has focused on group comparisons; therefore, its results are not applicable at the single-patient level. However, the recent development of support vector machine and similar analytical approaches promises to turn the field towards useful application in terms of diagnosis and prognosis at the single-patient level, thus being informative for daily clinical decisions.