Abnormal White Matter Microstructure in Posterior Cerebral Tracts Is Associated with Sensory Dysfunction and Impaired Multisensory Integration in Children with Sensory Processing Disorders

Background:

Sensory processing disorders (SPD) affect 5-16% of school-aged children and causes long-term deficits in intellectual and social development.  Current theories regarding the underlying basis of SPD implicate primary sensory cortical areas and higher-order multisensory integration (MSI) cortical regions.  The role of white matter in SPD has not been previously investigated.  We hypothesize that reduced microstructural integrity of white matter fibers in primary sensory tracts and/or in tracts projecting to multimodal association areas may result in loss of the precise timing necessary for sensory impulse propagation which serves sensory processing, integration, motor planning and the ability to suppress distracting stimuli. 

Objectives:

To test whether microstructural abnormalities of cerebral white matter are associated with sensory dysfunction, impaired MSI, and attention problems in children with SPD using diffusion tensor imaging (DTI).

Methods:

3 Tesla DTI was acquired in 16 boys with SPD and 24 age-, gender-, handedness- and IQ-matched neurotypical controls.  All subjects were ages 8-11 years, had full-scale IQ > 70, and a stable medication regimen for over 6 weeks.  Auditory, tactile, visual, multisensory, and inattention scores for all subjects were collected using the Sensory Profile, a parent questionnaire.  DTI was performed at 2.2-mm isotropic voxel resolution with 64 encoding directions at b=2000 s/mm².  FSL was used to calculate fractional anisotropy (FA), mean diffusivity (MD) and radial diffusivity (RD).  Nonparametric permutation testing from tract based spatial statistics (TBSS) was used to detect significant group differences in the white matter of the whole brain and to detect regions where DTI parameters were significantly correlated with behavioral variables (p<0.05, corrected for multiple voxel-wise comparisons).

Results:

Significant decreases in FA as well as increases in MD and RD were found in areas of cerebral white matter in the SPD cohort relative to controls, primarily in posterior white matter tracts including the splenium and posterior body of the corpus callosum, the bilateral posterior corona radiata and the bilateral posterior thalamic radiations, including the optic radiations.  Significant positive correlations were observed between FA of specific frontal and posterior cerebral tracts and the auditory, multisensory, and inattention scores (r=0.5-0.7; p<0.001). Conversely, negative correlations were detected between RD and the multisensory and inattention scores (r=0.5-0.7; p<0.001).

Conclusions:

This is the first study to demonstrate reduced white matter microstructural integrity in SPD patients versus matched controls.  We show that DTI microstructural parameters in posterior tracts correlate strongly with sensory dysfunction and abnormal MSI, while left frontal tract integrity correlates specifically with a behavioral measure of attention.  These findings suggest abnormal white matter as a biological basis for SPD and also help to establish SPD as a distinct disease separate from overlapping clinical conditions such as autism and ADHD which, at the level of group analysis, have divergent patterns of abnormality on DTI. Using brain-behavior correlations, we hope to move towards a more individualized model for understanding and treating children with sensory processing differences.