A 3-tier classification of cerebral arteriovenous malformations

Clinical article

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The authors propose a 3-tier classification for cerebral arteriovenous malformations (AVMs). The classification is based on the original 5-tier Spetzler-Martin grading system, and reflects the treatment paradigm for these lesions. The implications of this modification in the literature are explored.


Class A combines Grades I and II AVMs, Class B are Grade III AVMs, and Class C combines Grades IV and V AVMs. Recommended management is surgery for Class A AVMs, multimodality treatment for Class B, and observation for Class C, with exceptions to the latter including recurrent hemorrhages and progressive neurological deficits. To evaluate whether combining grades is warranted from the perspective of surgical outcomes, the 3-tier system was applied to 1476 patients from 7 surgical series in which results were stratified according to Spetzler-Martin grades.


Pairwise comparisons of individual Spetzler-Martin grades in the series analyzed showed the fewest significant differences (p < 0.05) in outcomes between Grades I and II AVMs and between Grades IV and V AVMs. In the pooled data analysis, significant differences in outcomes were found between all grades except IV and V (p = 0.38), and the lowest relative risks were found between Grades I and II (1.066) and between Grades IV and V (1.095). Using the pooled data, the predictive accuracies for surgical outcomes of the 5-tier and 3-tier systems were equivalent (receiver operating characteristic curve area 0.711 and 0.713, respectively).


Combining Grades I and II AVMs and combining Grades IV and V AVMs is justified in part because the differences in surgical results between these respective pairs are small. The proposed 3-tier classification of AVMs offers simplification of the Spetzler-Martin system, provides a guide to treatment, and is predictive of outcome. The revised classification not only simplifies treatment recommendations; by placing patients into 3 as opposed to 5 groups, statistical power is markedly increased for series comparisons.

Abbreviations used in this paper: AVM = arteriovenous malformation; mRS = modified Rankin Scale; ROC = receiver operating characteristic; RR = relative risk.

Article Information

Address correspondence to: Robert F. Spetzler, M.D., c/o Neuroscience Publications, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, Arizona 85013. email: neuropub@chw.edu.

Please include this information when citing this paper: published online October 8, 2010; DOI: 10.3171/2010.8.JNS10663.

© AANS, except where prohibited by US copyright law.



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    Diagrammatic representation of the combinations of graded variables (size, eloquence, and venous drainage) for each class of AVM. The Spetzler-Martin system assigns a score of 1 for small AVMs (< 3 cm), 2 for medium (3–6 cm), and 3 for large (> 6 cm). The eloquence of adjacent brain is scored as either noneloquent (0) or eloquent (1). The venous drainage is scored as superficial only (0) or including drainage to the deep cerebral veins (1). Scores for each feature are totaled to determine the grade. In the system described in this article, Class A includes Spetzler-Martin Grades I and II; Class B includes Grade III; and Class C includes Grades IV and V. Modified from Spetzler and Martin. (Modified with permission from Spetzler RF, Martin NA: A proposed grading system for arteriovenous malformations. J Neurosurg 65:476–483, 1986.)



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