title: Occlusive hyperemia: a radiosurgical phenomenon?
abstract: OBJECTIVE
  Causes of neurological deficits after arteriovenous malformation (AVM) radiosurgery, including hemorrhage, radiation injury, and delayed cyst formation, are described.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Neurological Surgery, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA. pollock.bruce@mayo.edu
authors.forename: B E
authors.initials: BE
authors.lastname: Pollock
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply*; D002550:Cerebral Veins / Q000473:pathology*; D006439:Hemodynamics; D006801:Humans; D006940:Hyperemia / Q000175:diagnosis*; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis*; D016634:Radiosurgery / Q000295:instrumentation*; D020246:Venous Thrombosis / Q000175:diagnosis*