Fig 4.

Schematic diagram of the PCT patterns in patients with brain AVM. Fast shunting of flow is noted in the nidus of the AVM. Blood flow in the normal brain parenchyma is seen (normal). Sump effect from the vascular pedicle supplying the shunt causes functional steal (pattern 1) in the brain adjacent to this pedicle (area A). Areas supplied by indirectly recruited collateral flow to the shunt from adjacent arteries cause ischemic steal (area B, pattern 2). High-pressure flow in the draining veins of the AVM causes venous congestion in remote parts of the brain (area C, pattern 3).