Early Draining Vein Occlusion Following Gamma Knife Surgery For Arteriovenous Malformations

Chun-Po Yen1, Jason P. Sheehan, PhD2, Lucia Schwyzer3, Matjaz Vorsic3, Ladislau Steiner3

1CHARLOTTESVILLE, VA United States 2Department of Neurosurgery, University of Virginia 3University of Virginia, Charlottesville, USA

Keywords: arteriovenous malformation, radiosurgery, gamma knife, hemorrhage, outcome

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     The role of Gamma Knife surgery (GKS) in the management of intracranial arteriovenous malformations (AVMs) is widely recognized. Acute side effects following Gamma procedures are uncommon. Increased signal on T2 magnetic resonance images (MRI) interpreted as radiation induced changes or brain edema is a common short to mid-term complication. Cyst formation and secondary tumors are remote morbidities that have been reported. 
     Early draining vein occlusion with resultant brain edema or hemorrhage, although well established in surgical series, was not described in radiosurgical literature until recently.
     From May 1989 to December 2008, 1512 patients underwent GKS for cerebral AVMs or dural arteriovenous fistulas at the University of Virginia. In 1329 patients, MRI following GKS was available for analysis of radiation induced changes/brain edema and early draining vein occlusion.
     Following GKS, a total of 463 patients (35%) developed radiation induced changes/brain edema surrounding the treated nidi. Among these patients, 12 patients were found to have early thrombosis of draining vein accompanied with the radiation induced changes.
      The venous thrombosis and radiation induced changes occurred six to 25 months (mean 12.9 months) following GKS. Three patients were asymptomatic, three experienced headache, one had seizure and headache and five developed neurological deficits. Patients with neurological deficits were treated with corticosteroids; two of the patients recovered completely, one still had slight hemiparesis, one had short-term memory deficits, and one died from intracerebral hemorrhage. The clinical follow-up after the development of venous thrombus ranged from 10 days to 156 months with a mean of 59.3 months. Nine patients had angiography after the development of venous thrombosis; eight patients demonstrated a total obliteration of the nidus and in one patient, the nidus remained patent. Three patients had only MRI follow-up showing no flow voids at the previous location of nidi in two patients and the nidus still patent in one patient.
     This was a retrospective study.
     Although venous structures are considered more radioresistant, endothelial damage accompanied with venous flow stasis might cause early venous thrombosis and premature venous occlusion following radiosurgery for AVMs. 
     In our series, all cases of venous thrombosis had a favorable outcome except one with a fatal hemorrhage.


Project Roles:

C. Yen (), J. Sheehan (), L. Schwyzer (), M. Vorsic (), L. Steiner ()