International Meeting for Autism Research (May 7 - 9, 2009): Transverse Relaxation Time Imaging of Frontal Lobe White Matter in Autism

Saturday, May 9, 2009

Northwest Hall (Chicago Hilton)

11:00 AM

R. Spring , Department of Psychiatry, University of Western Ontario, London, ON, Canada

N. Rajakumar , Department of Psychiatry, University of Western Ontario, London, ON, Canada

Y. Gagnon , Department of Medical Biophysics, University of Western Ontario, London, ON, Canada

D. Drost , Department of Medical Biophysics, University of Western Ontario, London, ON, Canada

R. Nicolson , Psychiatry, The University of Western Ontario, London, ON, Canada

Background: Transverse relaxation time (T2) is a quantitative Magnetic Resonance Imaging (MRI) technique that has the potential to increase our understanding of the aberrant brain development underlying autism. T2 is influenced by tissue water content, with longer T2 reflecting increased “free” water content. Previous studies by our group have found increases in total white matter T2 in patients with autism using automated region of interest (ROI) segmentation.

Objectives: The purpose of this study was to examine frontal lobe white matter T2 relaxation to determine if total white matter increases were localized to the frontal lobes which have been previously implicated in autism.

Methods: Nineteen males with autism (age: 9.2 ± 3.0 years) and 20 male controls (age: 10.7 ± 2.9 years) underwent a magnetic resonance imaging study at 3.0 Tesla. T2 and proton-density weighted images were acquired and quantitative T2 maps were generated from the GESFIDE MRI acquisition (Ma and Werhli, J. Magn. Reson. 111:61-69, 1996). Right, left and total frontal lobe white matter were hand traced in Analyze and mean T2 was calculated in the selected regions.

Results: The groups did not differ significantly in demographic variables, although patients with autism did have a significantly lower verbal IQ. Preliminary results on a subset of 14 patients and 14 controls revealed that patients with autism had a significant increase in total frontal white matter T2 (p<0.04). There were no significant group differences in left or right frontal white matter T2.

Conclusions: The present results need to be considered as preliminary, particularly given the small sample size and the inclusion of males only. The increases in frontal white matter T2 in patients with autism likely reflects increased tissue water, which is consistent with other studies indicating an increase in the volume of frontal white matter in autism. The increased tissue water could be secondary to fluid within myelin or inflammation, either of which could cause abnormalities of neurotransmission within the frontal lobes and reduced cortical connectivity.

See more of: Poster V
See more of: Poster Presentations