This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
A brain arteriovenous malformation (AVM) is a tangle of abnormal vessels, the nidus, where arteries connect directly to veins without the normal capillary network. It can bleed, cause seizures or headaches, or be found by chance on a scan. The Spetzler-Martin grade, published by Robert Spetzler and Neil Martin in 1986, estimates the risk of surgical removal.
The grading
| Feature | Points |
|---|---|
| Size of the nidus under 3 cm | 1 |
| Size 3 to 6 cm | 2 |
| Size over 6 cm | 3 |
| Eloquent location | 1 |
| Deep venous drainage | 1 |
Eloquent brain includes the sensorimotor, language and visual cortex, the thalamus and hypothalamus, the internal capsule, the brainstem, the cerebellar peduncles and the deep cerebellar nuclei. Deep drainage means that at least one vein drains into the deep venous system (such as the internal cerebral veins or the vein of Galen) rather than the cortical veins.
Grades run from I to V; a sixth category is used for inoperable lesions.
Three-tier classification
Ponce and Spetzler simplified the grades in 2011:
| Class | Grades | Usual approach |
|---|---|---|
| A | I and II | surgery, with low risk |
| B | III | treatment chosen case by case (surgery, radiosurgery, embolization) |
| C | IV and V | usually observation, unless repeated bleeding or progressive deficits |
Lawton-Young supplementary grade
Michael Lawton and colleagues added three factors in 2010: age (under 20: 1, 20 to 40: 2, over 40: 3 points), bleeding (unruptured: 1, ruptured: 0) and diffuse nidus (1). Adding the two grades gives a combined score from 2 to 10; a combined score of 6 or less was associated with an acceptable risk of new neurological deficit after surgery.
Example
A 4 cm AVM in the motor cortex (2 + 1) with superficial drainage is grade III. In a 35-year-old (2) with an unruptured (1), compact (0) nidus, the supplementary grade is 3 and the combined grade 6.
Treatment decisions
For unruptured AVMs, the ARUBA trial (2014) found that medical management alone led to fewer strokes and deaths over a few years than intervention, a result still debated for low-grade lesions. Decisions are taken by a multidisciplinary team of neurosurgeons, interventional neuroradiologists and radiation oncologists.