Objective To investigate cerebral structural signatures of the bulbar- and spinal-onset amyotrophic lateral sclerosis (ALS) using voxel-based morphometry on magnetic resonance imaging.Methods The MR structural images of the brain were obtained from 65 ALS patients (15 bulbar-onset, 50 spinal-onset) and 65 normal controls (NC) on a 3.0T MRI system. Gray matter (GM) volume changes were investigated by voxel-based morphometry, and the distribution of the brain regions with volume changes was compared between ALS and normal controls, as well as between bulbar-onset and spinal-onset ALS based on Neuromorphometrics atlas.Results On voxel-level the decreased volume of brain regions in ALS patients was located in the right precentral gyrus (rPrcGy) and right middle frontal gyrus compared with that in NC. The bulbar-onset ALS presented extra-motor cortex atrophy (fronto-temporal pattern), including left medial orbital gyrus, left inferior temporal gyrus and right middle temporal gyrus; the spinal-onset ALS suffered from motor cortex atrophy (rPrcGy dominance) and extra-motor cortex atrophy (fronto-temporal and extra-fronto-temporal pattern) compared with NC. The spinal-onset ALS featured by GM volume loss of left postcentral gyrus and bulbar-onset ALS featured by GM volume loss of left middle temporal gyrus compared with each other.Conclusions The asymmetric GM atrophy of the motor cortex and extra-motor cortex represents the common MRI structural signatures of spinal-onset ALS, and sole extra-motor cortex atrophy represents the structural signatures of bulbar-onset ALS. The present study also demonstrated that the pattern of GM damage is likely to distribute wider in spinal-onset ALS than in bulbar-onset ALS.

Key words: amyotrophic lateral sclerosis, gray matter, magnetic resonance imaging, precentral gyrus, voxel-based morphometry