International Meeting for Autism Research (London, May 15-17, 2008): White Matter Integrity in Patients with Autism Spectrum Disorders

Friday, May 16, 2008

Champagne Terrace/Bordeaux (Novotel London West)

9:30 AM

D. K. Shukla , Dept of Psychology, San Diego State University, San Diego, CA

B. M. Keehn , Joint Doctoral Program Language and Communicative Disorders, San Diego State University and University of California, San Diego, San Diego, CA

E. L. Grenesko , Dept of Psychology, San Diego State University, San Diego, CA

M. Shen , Dept of Psychology, San Diego State University, San Diego, CA

A. J. Lincoln , Alliant International University, Los Angeles, CA

R. A. Mueller , Dept of Psychology, San Diego State University, San Diego, CA

Background:

Autism Spectrum Disorders (ASD) are pervasive neurodevelopmental conditions that are characterized by atypical behavioral profiles including deficits in social reciprocity and communication. Recent MRI studies have shown that white matter tissue is affected in patients with ASD. This may impair the brain tissue connectivity resulting in neurofunctional defects.

Objectives:

The aim of this study was to assess the integrity of whole brain white matter tissue in patients with ASD.

Methods:

Diffusion tensor imaging (DTI) data of 6 children with ASD and 7 typically developing (TD) children was acquired from a 3T MRI scanner using single-shot diffusion-weighted EPI pulse sequence with two degrees of diffusion weighting (b=0 and 2000 s/mm², 15 non-linear directions, four repetitions). Geometric distortions due to local magnetic field inhomogeneities were corrected using field maps. DTI data were analyzed for fractional anisotropy (FA), mean diffusivity (MD), axial and radial diffusion of the whole brain with 80 percent probability for white matter tissue classification. Between group comparisons were performed using Wilcoxon Signed Ranks tests.

Results:

A significant difference between ASD and TD groups was observed for FA, MD and radial diffusion. In the ASD group, FA was significantly lower (0.23 ± 0.05 for ASD versus 0.37 ±0.04 for TD (p=0.03)); mean diffusivity was significantly higher (0.69 ±0.05 versus 0.61 ±0.05 *10^-3 mm²/s (p=0.03)), as was radial diffusion (0.60 ± 0.06 versus 0.48 ±0.05 *10^-3 mm²/s (p=0.03)). Decreased axial diffusion in the ASD group was non-significant (0.85 ± 0.03 versus 0.88 ± 0.04 *10^-3 mm²/s (p=0.17)).

Conclusions:

These results suggest widespread abnormalities in white matter tissue microstructure in patients with ASD. Significantly higher radial diffusion in ASD group may reflect disruption of myelin sheaths responsible for maintaining axonal integrity. Increasing sample sizes in the ongoing study will permit the examination of links between white matter integrity and cognitive performance.

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