Occlusive hyperemia: A radiosurgical phenomenon?

OBJECTIVE: Causes of neurological deficits after ateriovenous malformation (AVM) radiosurgery, including hemorrhage, radiation injury, and delayed cyst formation, are described. CONCEPT: Occlusive hyperemia has been described as a reason for neurological deterioration after AVM resection. Thrombosis of draining Veins or dural sinuses is thought to cause postoperative bleeding or neurological deficits secondary to venous hypertension, in a similar manner, local hemodynamic changes can occur in the brain adjacent to an AVM after radiosurgery if venous outflow is obstructed. Two patients are presented whose cases demonstrate this phenomenon. CONCLUSION: Patients can experience clinical worsening after AVM radiosurgery from premature thrombosis of draining veins. Local hemodynamic changes could explain why imaging changes thought to be radiation related occur more frequently after radiosurgery of AVMs than of tumors.