Table 1 Brain magnetic resonance imaging grading system.

Size of lesion	Grade
Just seen (<2 mm)	1
Small (2.1–5.0 mm)	2
Medium (5.1–10 mm)	3
Large (>10 mm)	4
Patchy confluent	5
Number of lesions
1	1
2–5	2
6–10	3
>10	4
Confluent	1–5

Total severity score = lesion size grade×lesion number grade.

Adapted from Cuadrado et al.⁹