The Spetzler Martin Grading Scale estimates the risk of open neurosurgery for a patient with AVM, by evaluating AVM size, pattern of venous drainage, and eloquence of brain location. A Grade 1 AVM would be considered as small, superficial, and located in non-eloquent brain, and low risk for surgery. Grade 4 or 5 AVM are large, deep, and adjacent to eloquent brain. Grade 6 AVM is considered not operable.

Note however, that this scale does not necessarily correlate with risk of treatment by embolization or radiosurgery.

Spetzler Martin Grading Scale

Size of AVM

Small (< 3 cm) 1
Medium (3-6 cm) 2
Large (> 6 cm) 3


Noneloquent site 0
Eloquent site* 1

Venouse drainage

Superficial 0
Deep 1

*Sensorimotor, language, visual cortex, hypothalamus, thalamus, brain stem, cerebellar nuclei, or regions directly adjacent to these structures.