3. Neuroimaging data MRI examinations were performed either at 1.5 or 3 Tesla for all the patients upon routine clinical care. Sequences included T1-weighted pre and post contrast, T2, Flair, diffusion, T2-Gradient Echo sequencing (T2-GRE). SWI was performed in only 5 patients and was thus not included in the analysis. Imagings of all patients were reviewed by two neurologists (SC, XA) and a neuroradiologist (NM). On the first MRI performed at diagnosis, confluent T2/FLAIR white matter hyperintensity (WMH) Figure 1A, size was characterized using a qualitative score as follow: small (<50% of one lobe), medium (>50% of one lobe and less than an entire lobe) and large (the volume of confluent WMH uni or multifocal exceeding one lobe), and mass effect was classified as mild (sulcal effacement), moderate (mass effect on the lateral ventricle) or severe (subfalcine herniation).