In 1986, Spetzler et al. classified it into the following 5 grades. The grading performance and scoring criteria of cerebral arteriovenous malformation were as follows: (1) size of vascular malformation: 1 point for small (<3 cm), 2 points for medium (3-6 cm), and 3 points for large (>6 cm); (2) adjacent functional brain area: 0 points for non-functional area and l points for functional area; (3) draining veins: 0 points for shallow and 1 point for deep. Grading method: Grade = (size of vascular malformation + functional area + drainage vein). Grade Ⅰ: l points. Grade II: 2 points. Grade III: 3 points. Grade IV: 4 points. Grade V: 5 points.