[Stereotaxic irradiation of 46 cerebral angiomas. Analysis of the angiographic results 2 and a half years after treatment]

Between May 1986 and March 1987, 46 small and medium sized cerebral arteriovenous malformations (AVM) were treated by radiosurgery in Paris. The stereotaxic coordinates of the lesions were determined according to the method of J. Talairach and the total radiation dose was delivered on spherical or ovoid target volumes with minibeams of 18 MV photons, using the technique developed by Osvaldo Betti. A review of the cases was undertaken in december 89. Twenty-one patients had previously been treated by embolization and/or surgery (46.6%). During the 25 to 40 months follow-up there were only 2 recurrences of bleeding (4.3). Control arteriography was performed in 38 cases (38/46 = 82.6%). There were thirteen cases of total disappearance of the AVM (13/36 = 34.2%), 17 incomplete obliterations (44.7%) and 9 (23%) arteriographies failed to show any radiological improvement. Eight patients had no arteriographic follow-up: 2 of them experienced a recurrence of bleeding and died before the planned arteriography, 1 was lost to follow-up and 5 patients refused control arteriography. A multidisciplinary team is needed to study the shape, the volume, the hemodynamic features of the AVM and the dosimetry in order to attain the best definition of the target volume and of the dose distribution. It seems that when the target volume included the nidus and the venous collector, follow-up arteriography results were satisfactory. Even though the optimum dose is yet to be determined, our results imply that a dose distribution allowing for 25 grays at the periphery of the AVM (isodose 70%) seems sufficient provided that the target volume is included within the 25.00 Gy isodose curve.