**6. Surgical resection**

## **6.1 Patient selection and outcome predictors**

The SM grading system for predicting patient outcome is microsurgery-based and remains the gold standard in the field [36]. Though the physiological origins of each AVM's clinical presentation are unknown, SM and supplemental grading systems have been validated on numerous occasions (see above). These systems apply to both patient selection and outcome prediction. Recently, Kim et al. demonstrated, in a cohort study performed on 1009 AVM patients at four institutions, that supplemented SM grades (SM-Supp, also considering the patient age, bleeding history, and compact anatomy indication) have greater predictive accuracy than standalone SM grades [90]. Their findings are not unique in that they show improvement over SM. They also rightfully conclude that "current grading systems are imperfect and evolving and that as the pathophysiology, hemodynamics, and genetics of AVMs are elucidated through research, grading systems will incorporate these advances." We, however, believe that there is a great difference between academic and clinical settings. We acknowledge that complex grading schemes may present improved predictability and selection capability. However, we believe practitioners must be provided with simple, intuitive, and relatively easy-to-use schemes. Only

#### *Advocating Intraluminal Radiation Therapy in Cerebral Arteriovenous Malformation Treatment DOI: http://dx.doi.org/10.5772/intechopen.89662*

such schemes will be readily accepted and rapidly/easily implemented in clinical settings, particularly in emergency cases. We, therefore, recommend that the factors incorporated into future grading schemes remain relatively accessible (direct) and limited in number.
