Based on the AVM size, location in eloquent areas, and presence of deep venous drainage, the scores are summed to range from 1 to 5, corresponding to grades I to V. The higher the grade, the greater the surgical difficulty and poorer the prognosis. Large AVMs completely located in eloquent areas or involving the hypothalamus and brainstem are considered grade 6, with extremely high risks for any treatment method.

Patients with Spetzler-Martin grades I to II are strongly recommended for surgical treatment. For grade III patients, a combination of endovascular embolization followed by microsurgery is recommended. For grades IV or V, the complications and mortality rates of surgical resection are significantly higher, thus surgical treatment is not recommended for these patients.

Volume refers to the maximum diameter of the lesion on an unmagnified angiogram (related to factors affecting AVM resection difficulty, such as feeding arteries and steal phenomenon).

Eloquent areas refer to the sensorimotor, language, and visual cortices, hypothalamus and thalamus, internal capsule, brainstem, cerebellar peduncles, and deep cerebellar nuclei.