MRI predictors of long-term evolution in amyotrophic lateral sclerosis

We investigated whether conventional and diffusion tensor (DT) magnetic resonance imaging (MRI) features of the corticospinal tract (CST) contribute to the prediction of the long-term clinical evolution in patients with amyotrophic lateral sclerosis (ALS). Brain conventional and DT MRI were obtained from 18 healthy subjects and 24 patients with sporadic ALS. Mean diffusivity (MD) and fractional anisotropy (FA) of the CST were obtained. Patients were scanned at baseline, then entered a longitudinal clinical follow-up. The ALS Functional Rating scale (ALSFRS) progression rate during follow-up was estimated. Patients were followed up prospectively for a median period of 3.4 years. Two patients were lost at follow-up and eight died during the observation period. The mean ALSFRS progression rate was 0.7/month (range = 0.0-2.0/month). At baseline, ALS patients showed significantly increased MD and decreased FA of the CST compared with controls. CST FA was associated with ALSFRS progression rate. ALSFRS deterioration rate and CST FA were independent predictors of survival in ALS patients. Survival at year 3 was 42% in patients with CST FA < 0.56 compared with 90% in patients with CST FA > 0.56. This study shows that more severe CST DT MRI abnormalities predict a poorer long-term clinical outcome in ALS patients. DT MRI of the brain has the potential to offer in vivo markers of disease severity.