Grading of supratentorial arteriovenous malformations on the basis of multivariate analysis of prognostic factors.

The case histories and angiograms of 93 consecutive patients who underwent surgery for arteriovenous malformations were analyzed retrospectively to find clinical and radiological prognostic factors influencing the outcome. A stepwise multiple regression was performed as follows. All radiological data such as size, location, and feeding and draining vessels as well as the clinical data such as age, sex, clinical grade on admission were introduced into the model and tested whether they contributed significantly to the prediction of the outcome which was the target variable. If so they were retained, otherwise eliminated. By this procedure the following features were identified as significant prognostic factors which adversely influence the outcome: poor clinical grade, feeding vessels from the A 1-segment and the anterior communicating artery, feeders from the M 1-segment, feeders from the Rolandic branches of the middle cerebral artery, a shunt through the anterior communicating artery. Neither the presence of a particular draining vein nor the type of the venous drainage when divided into superficial or deep had an influence on the outcome. Nor was the size of the lesion of significant importance. The bearing of these findings on the value of established grading systems is discussed and a new grading system is proposed.