MRI Morphometry of Basal Ganglia in Children with Pervasive Developmental Disorders

Background: In the last decade, neuroimaging studies suggested that basal ganglia (BG: caudate nucleus, putamen and globus pallidus) are involved in the third diagnostic domain of pervasive developmental disorders (PDDs), i.e. repetitive interests, behaviours and activities (RIBAs). In particular, few reports (Sears et al., 1999; McAlonan et al., 2002; Hollander et al., 2005; Rojas et al., 2006) explored specifically the relationship between caudate volumes and RIBAs in PDDs. To our knowledge, however, no studies of this kind were reported on samples exclusively composed of children. On the other hand, caudate nucleus is also a structure of fronto-striatal circuit that supports executive cognitive functions, often impaired in PDDs and a recent study (Voelbel et al., 2006) founded an inverse correlation between caudate volume and neuropsychological test performance in PDDs children. Furthermore, an inverse correlation between IQ and RIBAs (Cuccaro et al., 2003; Szatmari et al., 2006), and in particular with the lower order subgroup "sensory and motor repetitive behaviours" (Carcani-Rathwell et al., 2006), has been recently reported.

Objectives: This project attempts to further assess BG morphometry in PDDs children versus matched controls. Work is in progress in order to evaluate the effects of RIBAs (assessed through the ADI-R Repetitive and Stereotyped Behavior Domain) and IQ on BG volumes.

Methods: Twenty-seven patients (19 male, 8 female) meeting DSM-IV criteria for PDDs (mean age: 66 months +/- 22) and eighteen demographically matched controls underwent a 1,5 T MRI T1 weighted acquisition. The children with PDD were evaluated with ADOS–G and with ADI-R. Patients resulted with or without associated mental retardation at non verbal IQ evaluated through WISC-R or Leiter-R (if the subject was nonverbal), while controls are composed of typically developing children. The PDDs partecipants had normal results on screening tests for inborn errors of metabolism, normal chromosomal constitution and negative test for fragile X syndrome. Exclusion criteria included severe sensory problems, significant motor impairments or progressive neurological disorders. All the subjects were medication-naive. The anatomical T1-weighted volume is automatically segmented and meshed using Freesurfer software and BG volumes were compared between the two groups. BG have been separated into caudate, putamen and pallidus based on the regional anatomy and the volumetry of the separate structures has been analytically determined.

Results: Preliminary data indicate that differences between groups on caudate volume are not statistically significative. Nevertheless, in a subgroup of PDDs patients is possible to detect a caudate volume significantly larger then in controls. Further analysis is needed in order to correlate clinical variables with anatomical volumes.

Conclusions: These preliminary results do not give any evidence of statistically significative differences in caudate nucleus volume between PDDs children and controls. However, the hypotesis of a significant statistical correlation between BG volume with age, IQ and RIBAs scores in PDDs children calls for further investigations.