Diffusion tensor MRI of the corpus callosum in amyotrophic lateral sclerosis

To determine if decline in corpus callosum (CC) white matter integrity in patients with amyotrophic lateral sclerosis (ALS) is localized to motor-related areas.

Twenty-one ALS patients and 21 controls participated. Diffusion tensor images (DTI) were acquired using 3 Tesla (T) MRI. Tract-based spatial statistics were used to examine whole-brain white matter damage. A segmentation schema was used to define CC volumes-of-interest (VOI). Fractional anisotropy (FA) and radial- and axial-diffusivity (RD, AD) were extracted from VOIs and compared between groups. DTI measurements in motor-related Area III were tested for correlation with symptoms and disease duration.

Extracted FA values from CC VOIs were reduced in ALS patients (P≤0.0001), particularly in Areas II and III (P≤0.01). Reduced FA in Area III correlated with disease symptomology (P≤0.05) and duration (P≤0.02). Between-group whole-brain comparisons (P≤0.05, corrected) showed reduced FA and increased RD throughout white matter regions including the CC, corona radiata, and internal capsule. AD was increased in the left corona radiata and internal and external capsules.

FA in motor-related regions of the CC is more affected than other CC areas in ALS patients. Microstructural pathology of transcallosal fiber tracts may represent a future component of an imaging biomarker for ALS.