The diagnostic value of cortical thickness measures and diffusion tensor MRI metrics in the clinical phenotypes of MND (P6.088)

Objective. To test the diagnostic ability of the cortical thickness of the primary motor cortex (PMC) and diffusion tensor (DT) indices of the corticospinal tracts (CST) and corpus callosum (CC) in a large sample of patients with different motor neuron disease (MND) phenotypes. Background. There is no test available to make a reliable diagnosis and predict disease course early in amyotrophic lateral sclerosis (ALS) and other MND. MRI allows accurate measurements of cortical thickness and white matter (WM) abnormalities. Methods. 171 MND patients and 59 healthy controls underwent T1-weighted and DT MRI. We included 57 classic ALS, 22 bulbar ALS, 19 pyramidal ALS, 45 pure upper motor neuron (PUMN), and 28 pure lower motor neuron (PLMN). Cortical thickness of PMC bilaterally and DT MRI measures from the CST and CC fibers linking the PMC and supplementary motor area (SMA) were obtained. MRI feature individual classification was assessed. Results. Relative to controls, all MND groups showed thinning of the PMC, while damage to CST and CC motor fibers bilaterally was found in all phenotypes except for PLMN. MRI predictors providing optimal classification of each clinical phenotype were: CC-PMC FA (p<0.001) and right PMC thickness (p=0.005) with an accuracy of 71.2[percnt] in classic ALS; CC-PMC FA (p<0.001) with an accuracy of 93.2[percnt] in pyramidal ALS; CC-PMC FA (p<0.001) with an accuracy of 90.5[percnt] in PUMN; and right PMC thickness (p=0.02) with an accuracy of 71.5[percnt] in bulbar ALS and 71.9[percnt] in PLMN. The combination of DT MRI and cortical thickness measures provided an accuracy of 98[percnt] in distinguishing PUMN from PLMN. ALSFRS-R and UMN score correlated with CST and CC damage. Conclusions. Cortical thickness measures and DT MRI provide a sensitive quantitative method for distinguishing patients with MND at the individual level with high accuracy. Supported by: Italian Ministry of Health (#RF-2010-2313220).