Clinical correlations of grey matter reductions in the caudate nucleus of adults with attention deficit hyperactivity disorder

Abstract

Background: Magnetic resonance imaging (MRI) studies have shown decreased caudate volumes in individuals with attention deficit hyperactivity disorder (ADHD). However, most of these studies have been carried out in male children. Very little research has been done in adults, and the results obtained in children are difficult to extrapolate to adults. We sought to compare the volume of the caudate of adults with ADHD with that of healthy controls; we also compared these volumes between men and women.

Methods: We performed an MRI scan on 20 adults with ADHD (10 men and 10 women) aged 25-35 years and 20 healthy controls matched by age and sex. We used voxel-based morphometry with the DARTEL algorithm for image analyses. We used the specifically designed Friederichsen, Almeida, Serrano, Cortes Test (FASCT) to measure the severity of ADHD; both the self-reported (FASCT-SR) and the observer (FASCT-O) versions were used.

Results: The statistical parametric map showed a smaller region with low grey matter volume and a smaller concentration of grey matter in this region of the right caudate in ADHD patients than in health controls, both in the entire sample and within each sex. There was a significant correlation between the volume of this region of the caudate with the number of DSM IV-TR criteria, as well as with the total scores and most of the factors of the FASCT-SR and FASCT-O scales. A separate correlation analysis by sex gave similar results.

Limitations: The study design was cross-sectional.

Conclusion: The region of the right caudate with low grey matter volume was smaller in adults with ADHD in both sexes and was correlated with ADHD severity.

Fig. 1

Portion of the right caudate where voxel-based morphometry showed statistical differences in the concentration of grey matter between 20 adults with attention deficit hyperactivity disorder and 20 healthy controls. The statistical parametric mapping (SPM), design matrix and SPM projection over the Montreal Neurological Institute T1 template are shown. The SPM contrast was set at a p value threshold of 0.001 and a voxel threshold of 20. The settings for small volume correction with a volume-of-interest search were a radius of 10 mm at global maxima 18, 6 and 22.

Fig. 2

Portion of the right caudate where voxel-based morphometry showed statistical differences between 10 controls and 10 adults with attention deficit hyperactivity disorder (left) in men and (right) women. The statistical parametric mapping (SPM) projection over the Montreal Neurological Institute T1 template is shown. The SPM contrast was set at a p value threshold of 0.01 and a voxel threshold of 20. The settings for small volume correction in men with a volume-of-interest search were a radius of 5 mm at global maxima of x = 21, y = 9, z = 18, and the settings in women were a radius sphere of 5 mm at global maxima of x = 17, y = 0, z = 25.

Fig. 3

Comparison by sex of the volume of the portion of the right caudate where voxel-based morphometry (VBM) showed differences in the concentration of grey matter between healthy controls and patients with attention deficit hyperactivity disorder (ADHD). The bars represent the mean volume of the portion of the right caudate where VBM showed differences in concentration between healthy and ADHD individuals. *t₁₈ = 2.36, p = 0.029, difference between means = 36 mm³, 95% confidence interval (CI) 4–68 mm³, Cohen d = 1.11. **t₁₈ = 2.32, p = 0.032; difference between means = 20 mm³, 95% CI 2–48 mm³, Cohen d = 1.09. SE = standard error.