An ideal grading system would define, for each specific AVM, the degree of difficulty involved in safely removing the malformation. Such a grading system should provide a reasonably accurate estimation of operative morbidity and mortality, and be simple yet comprehensive enough to be readily applied to all cerebral AVM's. Previously proposed grading schemes, which have been based only on AVM size or on the number and distribution of feeding arteries, are simple enough to be easily applicable.8 These fail, however, to consider such important variables as anatomic location, degree of vascular steal, eloquence of adjacent brain, and pattern of venous drainage. Other systems are so complicated that they are difficult to be applied easily and rapidly.11 In order to correct these shortcomings a simple system that weighs the important features of an individual AVM, and thus grades the lesion according to its degree of surgical difficulty, is proposed.
The authors would like to thank Marjorie Medina, R.N., and Drs. Issam Awad and Daniele Rigamonti for independently assisting in grading the AVM's.
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