Volumetric abnormalities of basal ganglia 
have been associated with attention deficit hyperactivity disorder (ADHD) especially in boys. ADHD is a prevalent neuropsychiatric syndrome characterized by excessive difficulty with focusing attention, sitting still and controlling impulses. Before the era of neuroimaging, neurologists reported motor impairments and cognitive anomalies that implicated the frontal lobe. Among these subcortical regions, the basal ganglia have been particularly emphasized because they are important for selecting appropriate goal-directed behavior.
The authors examined the effects of ADHD, sex and their interaction on the shapes and sizes of three basal ganglia structures (caudate, putamen, globus pallidus) by using large deformation diffeomorphic metric mapping (LDDMM). LDDMM mappings from 35 typically developing children were used to generate basal ganglia templates. The basal ganglia (caudate, putamen, globus pallidus) were manually delineated on magnetic resonance imaging from 66 typically developing children (35 boys) and 47 children (27 boys) with ADHD. Shape variations of each structure relative to the template were modeled for each subject as a random field using Laplace-Beltrami basis function in the template coordinates. Linear regression was used to examine group differences in volumes and shapes of the basal ganglia.
Boys with ADHD showed significantly small basal ganglia volumes compared with typically developing boys, and LDDMM revealed the groups differed to a large degree in the shapes of the various structures that make up the basal ganglia. Volume compression was seen bilaterally in the caudate head and body, the anterior putamen, the left anterior globus pallidus, and the right ventral putamen. Volume expansion was most pronounced in the posterior putamen. No volume or shape differences were revealed in girls with ADHD.
The shape compression pattern of basal ganglia in boys with ADHD suggests that ADHD-associated deviations from typical brain development involved multiple frontal-subcortical control loops, including circuits with premotor, oculomotor, and prefrontal cortices. Further investigations employing brain-behavior analyses will help to discern the task-dependent contributions of these circuits to impaired response control that is characteristic of ADHD.
COMMENT:
The finding that girls with ADHD did not exhibit differences in basal ganglia volume and shape when compared with normally developing girls suggests several possibilities:
♣ The underlying neuropathophysiologic processes in boys and girls with ADHD is fundamentally different.
♣ The core neuroanatomic abnormalities for girls with ADHD are to be found elsewhere, but not in the basal ganglia.
♣ The seeming correlation between smaller basal ganglia volumes together with shape compression and ADHD in boys may mask a subtler problem, suggesting that a good research path would be to do an in-depth comparison of the brains of girls with ADHD and normally-developing girls.
To read this study in its entirety, go to Am J Psychiatry 166:1 January 2009, pp. 74-82.
-–Cynthia Haggard is a medical writer and teacher who lives in Washington DC. She owns her own business, Clarifying Concepts, which provides technical writing, writing for the public, teaching, and regulatory affairs services. To see more, please go to clarifyingconcepts. (c) 2009 All rights reserved.
As far as I know this research is ongoing. I expect that we will hear more sometime next year. Stay tuned.