The outcomes of 151 patients with arteriovenous malformations (AVMs) treated either surgically or conservatively are presented. In terms of long-term survival rate and follow-up results, the patients who underwent total excision had more favorable results than did those treated conservatively. Patient age was the most important clinical factors, with the preoperative level of consciousness being the second most important. A grading system was formulated on the basis of the angiographical factors by using multiregression analysis; the size of the AVM influenced the surgical outcome twice as much as did the location and the pattern of arterial feeding. Thus, a large AVM (≥4 cm) was given 2 points; a small AVM (<4 cm) was given 0 points; a deep AVM was given 1 point; a superficial AVM was given 0 points; an AVM supplied by three of more artery systems was given 1 point; and an AVM supplied by one or two artery systems was given 0 points. AVMs were categorized into 5 grades from Grade 0 to 4 by the summation of these points. Predicted Karnofsky scale after surgery was calculated by this grading system and the following equation: predicted Karnofsky scale = 87.2 - 5.6 × Grade. Grade 0 and 1 AVMs showed high rates of total excision (Grade 0, 94%; Grade 1, 82%) and of satisfactory outcome (Grade 0, 90%; Grade 1, 82%) and were classified as “easy” lesions. Grade 2 AVMs are lesions classified as “moderate” and had a total excision rate of 76% and a satisfactory outcome rate of 71%. Grade 3 and 4 lesions should be considered to be AVMs classified as “difficult” and showed total excision rates of 64 and 67%, respectively, and satisfactory outcome rates of 64 and 33%, respectively. This gradient system is useful for predicting both the degree of surgical difficulty and the operative morbidity of AVMs and, hence, for deciding the surgical indications.
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Tamaki et al. (1991) studied this question.