Predictive Capability of the Spetzler-Martin versus Supplementary Grading Scale for Microsurgical Outcomes of Cerebellar Arteriovenous Malformations

The recently described supplementary grading scale may be superior to the widely used Spetzler-Martin grading scale in the prediction of microsurgical outcomes for cerebellar arteriovenous malformations (AVM). We report two cases of ruptured cerebellar AVMs with the same Spetzler-Martin grade but different supplementary grades treated with microsurgical resection. Both patients had symptomatic brainstem compression from cerebellar hematomas and subsequently underwent uncomplicated surgeries; however, their outcomes were significantly different. It has previously been proposed that AVMs distort cerebellar anatomy in a different manner than supratentorial cerebral anatomy thereby potentially resulting in misrepresentation when utilizing the Spetzler-Martin grading scale. However, the components of the supplementary grading scale are independent of cerebellar anatomy, which may explain why it has been shown to be better than the Spetzler-Martin grading scale for prediction of surgical outcomes. In addition, due to the smaller volume of the posterior fossa compared to the supratentorial compartment, rupture of cerebellar AVMs may result in rapid and catastrophic neurological compromise. Therefore, the role of microsurgery may be more critical for AVMs of the cerebellar than for those located elsewhere. Simple and effective grading systems are invaluable tools for clinical and surgical decision-making, although the decisions rendered should always be made in conjunction with the patient's presentation and the physician's experience.