Cerebellar Arteriovenous Malformation Grading

Cerebellar Arteriovenous Malformation Grading

Anatomic diversity among cerebellar arteriovenous malformations (AVMs) calls for a classification that is intuitive and surgically informative. Selection tools like the Spetzler-Martin grading system are designed to work best with cerebral AVMs but have shortcomings with cerebellar AVMs 1)

The objective of a study from the Department of Neurosurgery, University of California, San FranciscoBanner-University Medical Center TucsonArizona and Barrow Neurological Institute, Phoenix, was to evaluate the existing Spetzler-Martin AVM grading system (SM), Spetzler Ponce classification (SP), and Lawton-Young Grading System (LY) for cerebellar arteriovenous malformations (AVMs) and to propose a new grading system to estimate the risks associated with these lesions.

Data for patients with cerebellar AVMs treated microsurgically in two tertiary medical centers were retrospectively reviewed. Data from patients at institution 1 were collected from September 1999 to February 2013, and at institution 2 from October 2008 to October 2015. Patient outcomes were classified as favorable (modified Rankin Scale [mRS] score 0-2) or poor (mRS score 3-6) at the time of discharge. Using chi-square and logistic regression analysis, variables associated with poor outcomes were assigned risk points to design the proposed grading system. The proposed system included neurological status prior to treatment (poor, +2 points), emergency surgery (+1 point), age > 60 years (+1 point), and deep venous drainage (deep, +1 point). Risk point totals of 0-1 comprised grade 1, 2-3 grade 2, and 4-5 grade 3.

A total of 125 cerebellar AVMs of 1328 brain AVMs were reviewed in 125 patients, 120 of which were treated microsurgically and included in the study. With our proposed grading system, we found poor outcomes differed significantly between each grade (p < 0.001), while with the SM, SP, and LY grading systems they did not (p = 0.22, p = 0.25, and p = 1, respectively). Logistic regression revealed grade 2 had 3.3 times the risk of experiencing a poor outcome (p = 0.008), while grade 3 had 9.9 times the risk (p < 0.001). The proposed grading system demonstrated a superior level of predictive accuracy (area under the receiver operating characteristic curve [AUROC] of 0.72) compared with the SM, SP, and LY grading systems (AUROC of 0.61, 0.57, and 0.51, respectively).

Nisson et al., propose a novel grading system for cerebellar AVMs based on emergency surgery, venous drainage, preoperative neurological status, and age that provides a superior prognostication power than the formerly proposed SM, SP, and LY grading systems. This grading system is clinically predictive of patient outcomes and can be used to better guide vascular neurosurgeons in clinical decision-making 2).

Rodriguez-Hernandez et al. hypothesized that the predictive capability of the supplementary grading scale was superior to that of the Spetzler Martin grading scale for assessment of outcomes following microsurgical resection of cerebellar AVMs 3).

Deep venous drainage is a better indicator of the depth of the nidus for cerebral AVMs than for cerebellar AVMs. Cerebellar anatomy is altered by AVMs in a different manner than cerebral anatomy such that the supplementary grading scale may be better than the Spetzler-Martin grade for prediction of surgical outcomes. In comparison with ruptured cerebral AVMs, which may be managed conservatively followed by radiosurgery for achievement of obliteration, ruptured cerebellar AVMs may be better treated by surgical resection, especially when the associated hemorrhage results in symptomatic compression of surrounding neural structures.

In conclusion, the surgical risk for cerebellar AVMs may be predicted by either the Spetzler-Martin or supplementary grading scales, although the supplementary scale may show better correlation with outcomes 4) 5) 6). However, neither grading system can substitute for experienced clinical and surgical judgment 7).


1) , 3) , 5)

Rodríguez-Hernández A, Kim H, Pourmohamad T, Young WL, Lawton MT. University of California, San Francisco Arteriovenous Malformation Study Project. Cerebellar arteriovenous malformations: Anatomic subtypes, surgical results, and increased predictive accuracy of the supplementary grading system. Neurosurgery. 2012 Dec;71(6):1111–1124.

Nisson PL, Fard SA, Walter CM, Johnstone CM, Mooney MA, Tayebi Meybodi A, Lang M, Kim H, Jahnke H, Roe DJ, Dumont TM, Lemole GM, Spetzler RF, Lawton MT. A novel proposed grading system for cerebellar arteriovenous malformations. J Neurosurg. 2019 Mar 8:1-11. doi: 10.3171/2018.12.JNS181677. [Epub ahead of print] PubMed PMID: 30849761.

Lawton MT, Kim H, McCulloch CE, Mikhak B, Young WL. A supplementary grading scale for selecting patients with brain arteriovenous malformations for surgery. Neurosurgery. 2010 Apr;66(4):702–713. discussion 713.

Spetzler RF, Martin NA. A proposed grading system for arteriovenous malformations. J Neurosurg. 1986 Oct;65(4):476–483.

Ding D, Liu KC. Predictive Capability of the Spetzler-Martin versus Supplementary Grading Scale for Microsurgical Outcomes of Cerebellar Arteriovenous Malformations. J Cerebrovasc Endovasc Neurosurg. 2013 Dec;15(4):307-10. doi: 10.7461/jcen.2013.15.4.307. Epub 2013 Dec 31. PubMed PMID: 24729957; PubMed Central PMCID: PMC3983531.

Supplementary Spetzler-Martin AVM grading scale

Supplementary Spetzler-Martin AVM grading scale

In 2010Michael T. Lawton et. al introduced the Supplementary Spetzler-Martin AVM grading scale specifically to predict surgical outcomes in Ruptured cerebral arteriovenous malformation. The Supplemented Spetzler-Martin grading scale also included rupture status, age of the patient, and nidal architecture (diffuse versus focal). In the 300 patients in Lawton’s 2010 study, the supplemental Spetzler-Martin grading scale demonstrated a stronger correlation with surgical outcomes than the initial Spetzler-Martin AVM grading system (ROC 0.78 vs 0.66) 1).

This arteriovenous malformation (AVM) grading system supplements rather than replaces the well-established Spetzler-Martin AVM grading systemand is a better predictor of neurologic outcomes after AVM surgery. The supplementary grading scale has high predictive accuracy on its own and stratifies surgical risk more evenly. The supplementary grading system is easily applicable at the bedside, where it is intended to improve preoperative risk prediction and patient selection for surgery 2).

retrospective study was conducted on 200 patients admitted to the Helsinki University Hospital between 2000 and 2014. The validity of the Supp-SM and SM grading systems was compared using the area under the receiver operating characteristic (AUROC) curves, with respect to the change between preoperative and early (3-4 mo) as well as final postoperative modified Rankin Scale (mRS) scores.

The performance of the Supp-SM was superior to that of the SM grading scale in the early follow-up (3-4 mo): AUROC = 0.57 (95% confidence interval [CI]: 0.49-0.65) for SM and AUROC = 0.67 (95% CI: 0.60-0.75) for Supp-SM. The Supp-SM performance continued improving over SM at the late follow-up: AUROC = 0.63 (95% CI: 0.55-0.71) for SM and AUROC = 0.70 (95% CI: 0.62-0.77) for Supp-SM. The perforating artery supply, which is not part of either grading system, plays an important role in the early follow-up outcome (P = .008; odds ratio: 2.95; 95% CI: 1.32-6.55) and in the late follow-up outcome (P < .001; odds ratio: 5.89; 95% CI: 2.49-13.91).

The Supp-SM grading system improves the outcome prediction accuracy and is a feasible alternative to the SMS, even for series with higher proportion of high-grade AVMs. However, perforators play important role on the outcome 3).

Data collected from 1009 AVM patients who underwent AVM resection were used to compare predictive powers of Spetzler Martin grades (SM) and supplemented Spetzler-Martin grades (SM-Supp). Patients included the original 300 patients plus those treated thereafter (N=117), and an additional 592 patients from three other centers.

In the combined cohort, the SM-Supp system performed better than SM system alone: AUROC=0.75 (95% CI: 0.71 – 0.78) for SM-Supp and AUROC=0.69 (95% CI: 0.65 – 0.73) for SM (p< 0.001). Stratified analysis fitting models within three different follow-up groupings (<6 months, 6 months – 2 years, and >2 years) demonstrated that the SM-Supp system performed better than SM system for both medium (AUROC=0.71 vs. 0.62, p=0.003) and long follow-up (AUROC=0.69 vs. 0.58, p=0.001). Patients with SM-Supp grades ≤ 6 had acceptably low surgical risks (0 – 24%), with a significant increase in risk for grades above 6 (39% – 63%).

The study of Kim et al., validates the predictive accuracy of the supplementary grading system in a multicenter cohort. SM-Supp grade of 6 is a cut-off or boundary for AVM operability. Supplemented grading is currently the best method of estimating neurological outcomes after AVM surgery, and recommended as a starting point in the evaluation of AVM operability 4).



Lawton MT, Kim H, McCulloch CE, Mikhak B, Young WL. A supplementary grading scale for selecting patients with brain arteriovenous malformations for surgery. Neurosurgery. 2010 Apr;66(4):702-13; discussion 713. doi: 10.1227/01.NEU.0000367555.16733.E1. PubMed PMID: 20190666; PubMed Central PMCID: PMC2847513.

Lawton MT, Kim H, McCulloch CE, Mikhak B, Young WL. A supplementary grading scale for selecting patients with brain arteriovenous malformations for surgery. Neurosurgery. 2010 Apr;66(4):702-13; discussion 713. doi: 10.1227/01.NEU.0000367555.16733.E1. PubMed PMID: 20190666; PubMed Central PMCID: PMC2847513.

Hafez A, Koroknay-Pál P, Oulasvirta E, Elseoud AA, Lawton MT, Niemelä M, Laakso A. The Application of the Novel Grading Scale (Lawton-Young Grading System) to Predict the Outcome of Brain Arteriovenous Malformation. Neurosurgery. 2019 Feb 1;84(2):529-536. doi: 10.1093/neuros/nyy153. PubMed PMID: 29733392; PubMed Central PMCID: PMC6331307.

Kim H, Abla AA, Nelson J, McCulloch CE, Bervini D, Morgan MK, Stapleton C, Walcott BP, Ogilvy CS, Spetzler RF, Lawton MT. Validation of the Supplemented Spetzler-Martin Grading System for Brain Arteriovenous Malformations in a Multicenter Cohort of 1009 Surgical Patients. Neurosurgery. 2014 Sep 23. [Epub ahead of print] PubMed PMID: 25251197.

Consistency grading system

Dentro de las escalas, esta es una propuesta como sistema de clasificación del meningioma basado en su consistencia quirúrgica.

Proporciona una evaluación fiable, práctica y también cuenta la heterogeneidad en la consistencia del tumor.
La consistencia puede estandarizarse como base para estudios futuros relacionados con los resultados quirúrgicos, la previsibilidad de la consistencia y la vascularización mediante técnicas de neuroimagen, y la eficacia de los diferentes instrumentos quirúrgicos 1).
1) Zada G, Yashar P, Robison A, Winer J, Khalessi A, Mack WJ, Giannotta SL. A proposed grading system for standardizing tumor consistency of intracranial meningiomas. Neurosurg Focus. 2013 Dec;35(6):E1. doi: 10.3171/2013.8.FOCUS13274. PubMed PMID: 24289117.
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