Contribution to the Hemodynamics of Arterial Venous Malformations

In three cases of arteriovenous malformations (AVMs), and in one postoperative case, the passage of an I.V.-administered 99m-Technetium bolus through the brain and the 133 Xenon clearance after intracarotid injection from different brain areas were observed, using a scintillation camera-1600 channel memorydigital magnetic tape unit. Regional cerebral blood flow values from contiguous areas down to 12 mm lateral lengths were calculated. In two cases computer-calculated cerebral blood flow maps are presented. Areas surrounding the AVMs revealed relatively high CBF values, while the blood flow in more distant parts of the hemisphere was decreased. Areas of low CBF values were detected also in the postoperative case with ligation of vessels. The initial part of the washout curves showed over all AVMs shunt peaks up to 88% of the initial activity. Shunt peaks detected also over most parts of the involved hemisphere are explained by arterio-arterial shunt connections. Their flow, centripetally directed to AVM, may cause the observed pattern of higher and lower flow values, indicating that the Xenon washout may be sensitive not only to capillary flow. Conclusions are drawn that the Xenon-clearance technique provides detection of the hemodynamic influence, but not of the shunt volume of AVMs.