Figure 2. Semi-quantitative assessment of nPVSs severity. nPVS severity was assessed using a semi-quantitative scale (none/mild = 0/1, moderate = 2, frequent/severe = 3/4). The severity is shown in the basal ganglia (A), CSO (B), midbrain (C) and thalamus (D). nPVS, normal-sized perivascular space; BG, basal ganglia; CSO, centrum semiovale; FOG, freezing of gait; TD, tremor dominant; HCs, healthy controls; FOG(-), PD patients without FOG; FOG(TD), PD patients with FOG TD subtype; and FOG(TD-) PD patients with FOG, but non-TD subtypes.