Sociodemographic and clinical features of the three study groups.

Values are mean ± standard deviation [range] or number (%). P1 =  differences between all groups; P2 = differences between patient groups. *p<0.05 compared with healthy controls. Group differences in categorial variables (i.e., gender and onset type) were assessed using the Fisher Exact test. Continuous variables (i.e., age, WMH load, disease duration, ALSFRS-r, UMN score, and disease progression rate) were compared using the Kruskal-Wallis or the Mann-Whitney U-test. Disease progression rate = (48-ALSFRS-r score)/time from symptom onset. Abbreviations: ALSFRS-r =  ALS Functional Rating scale-revised; co =  cut-off; MMSE =  mini mental state examination; PLS-cd =  primary lateral sclerosis with cognitive deficits; PLS-cu =  cognitively unimpaired primary lateral sclerosis; UMN score =  upper motor neuron score; WMH =  white matter hyperintensity.