Can Brainstem Arteriovenous Malformations Be Safely Treated By Gamma Knife Surgery?

Keywords: arteriovenous malformation, gamma knife, brain stem, outcome, radiosurgery

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     To investigate efficacy and safety of Gamma Knife Surgery (GKS) for the treatment of brainstem AVM.
     Twenty patients with brainstem AVMs treated by GKS between 1993-2007 were enrolled for study. There were 7 men and 13 women with age ranged from 9-42 years. Fifteen patients received GKS once as the only and primary treatment, while another 5 patients underwent GKS twice to obtain a complete obliteration. Locations of AVMs included midbrain (15 cases), pons (7 cases) and medulla oblongata (2 cases).
      AVM volumes ranged from 0.721-21.5 ml. The maximum dose to AVM nidi varied from 24-37 Gy with marginal dose ranged from 15-25 Gy. After radiosurgery, patients underwent regular MRI follow-up, a final angiogram was performed 2-4 years after GKS to verify complete obliteration (CO).
     Eighteen patients (90%) had been followed for more than 24 months (median 37 months). Other two patients (10%) were followed less than 2 years. Varying degrees of AVM regression in MRI were observed in all patients. The angiographic follow-up after primary GKS in 15 patients revealed a CO rate of 67% (10/15). In five patients who failed to achieve CO after the first GKS, repeated treatment was performed. The second GKS resulted in CO of all 5 patients. Overall, the angiographic confirmed CO was obtained in 15 out of 20 cases (75%). Ten of 20 patients (50%) had no adverse radiation effect (ARE). Five patients (25%) had mild ARE without clinical manifestations. One patient (5%) with a large AVM involving midbrain and thalamus developed moderate ARE and complicated with motor weakness. Two patients (10%) had mild hemiparesis with rigidity due to late focal damage to cerebral peduncle. Two patients (10%) experienced mild brainstem hemorrhage after GKS, but recovered. There was no mortality in this study.
     This is a retrospective study.
     In this series, the cure rate of brainstem AVM was 75%, with treatment-related complications found in 3 patients (15%).
     The complications were mild to moderate that daily activities were not much disturbed. We suggest GKS can be the treatment of choice for brainstem AVMs.


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