What is the maximum Spetzler-Martin grade?

The scoring system yields grades I through V (maximum score = 5). Grade VI is a separate designation used by some centers for AVMs deemed too dangerous for any intervention, but it is not calculated from the numeric score.

What is considered deep venous drainage?

Award 1 point when any drainage reaches deep venous structures such as the internal cerebral veins, basal veins, or precentral cerebellar vein. Mixed superficial and deep drainage still meets this criterion; only exclusively superficial drainage scores 0.

How does the grade relate to surgical morbidity?

Grade I–II AVMs carry low surgical morbidity and are generally good surgical candidates. Grade III carries intermediate risk. Grade IV–V carry substantially higher risk of new neurological deficits, and many centers favor radiosurgery, staged embolization, or observation for these lesions.

Does this tool store patient data?

No. All calculations run entirely in your browser. No data is sent to any server.

Spetzler-Martin AVM Grade

Score AVM size, eloquence of adjacent brain, and venous drainage pattern to determine the Spetzler-Martin grade (I–V) and estimate surgical risk.

AVM Parameters

AVM Size (maximum nidus diameter)

Measured on angiography or MRI

Small (<3 cm) +1 pt Medium (3–6 cm) +2 pts Large (>6 cm) +3 pts

Eloquence of Adjacent Brain

Sensorimotor, language, visual cortex, thalamus, hypothalamus, internal capsule, brainstem, cerebellar peduncles, or deep cerebellar nuclei

Non-eloquent +0 pts Eloquent +1 pt

Venous Drainage Pattern

Based on cerebral angiography

Superficial drainage only +0 pts Deep drainage present (deep-only or mixed drainage) +1 pt

Select all three parameters and click Calculate

Spetzler-Martin Grade

Score Breakdown

AVM Size

Eloquence of Adjacent Brain

Venous Drainage

Total Score

Surgical Risk

Grade Reference

Grade	Score	Expected Morbidity
I	1	Very low (<3% new deficit)
II	2	Low (~3–5% new deficit)
III	3	Moderate (~7–15% new deficit)
IV	4	High (~17–22% new deficit)
V	5	Very high (>22% new deficit)

Morbidity estimates from Spetzler & Martin (1986). Outcomes vary by institution and technique. This tool is for educational and clinical support use only — not a substitute for specialist judgment.

Summary

Score AVM size, eloquence of adjacent brain, and venous drainage pattern to determine the Spetzler-Martin grade (I–V) and estimate surgical risk.

How it works

Measure the maximum diameter of the AVM nidus on angiography or MRI: small (<3 cm) = 1 point, medium (3–6 cm) = 2 points, large (>6 cm) = 3 points.
Determine whether the AVM is adjacent to eloquent brain (sensorimotor, language, visual cortex, thalamus, hypothalamus, internal capsule, brainstem, cerebellar peduncles, deep cerebellar nuclei): yes = 1 point, no = 0 points.
Identify the venous drainage pattern on angiography: any deep venous drainage, including mixed drainage, = 1 point; superficial-only drainage = 0 points.
Sum the three scores. The total (1–5) is the Spetzler-Martin grade.
Review the grade and associated expected surgical morbidity to support the treatment decision.

Use cases

Pre-operative risk stratification before AVM microsurgical resection.
Triage AVMs for radiosurgery vs. open surgery vs. embolization vs. observation.
Patient counseling on expected neurological outcomes after surgery.
Multidisciplinary tumor board and neurovascular conference presentations.
Medical education on AVM anatomy and surgical risk factors.
Documentation of AVM risk grade in clinical notes and operative planning records.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu