THE PROSPECTIVE APPLICATION OF A GRADING SYSTEM FOR ARTERIOVENOUS-MALFORMATIONS

THE DECISION-MAKING PROCESS whereby treatment is offered to a patient with an arteriovenous malformation (AVM) must be supported by an under standing of the risks related to the natural history of the AVM and th e risks related to the treatment of that particular AVM. The ability t o estimate the treatment risk for an individual patient is hampered by the marked variability in the complexity of AVMs. In 1986, an AVM gra ding system was proposed to predict surgical morbidity and mortality. This system is based on the AVM size, the neurological eloquence of ad jacent brain, and the pattern of venous drainage. Grade I malformation s are small, superficial, and located in noneloquent cortex; Grade V l esions are large, deep, and situated in neurologically critical areas; and Grade VI lesions are considered inoperable AVMs. A retrospective application of this grading scheme demonstrated its correlation with t he incidence of postoperative neurological complications. A prospectiv e application of the AVM grading system has been performed in 120 cons ecutive patients who had a complete microsurgical excision of their AV M, with or without AVM embolization. The AVM grading system accurately correlated with both new-temporary (P < 0.0001) and new-permanent (P = 0.008) neurological deficits. The permanent major neurological morbi dity rates for Grades I through III were 0%, increasing to 21.9% in pa tients with Grade IV and 16.7% in patients with Grade V AVMs (P < 0.00 01). One patient with a Grade III AVM died from an esophageal hemorrha ge 15 months after her AVM was treated. This prospective evaluation co nfirms the accuracy and utility of the proposed AVM grading system to assist with the process of management decision making. In addition, th e continued application of this standardized grading scheme will enabl e a comparison among various clinical series and among different treat ment techniques.