Long-term Results Of Combined Endovascular And Gamma Knife Surgery For Cerebral Arteriovenous Malformations

Keywords: gamma knife, endovascular embolization, embolization, arteriovenous malformation, outcome

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     To evaluate long-term imaging and clinical outcomes following combined embolization and Gamma Knife surgery (GKS).
     Between 1989 and 2008, 257 patients underwent the two procedures. Thirty-six (14%) were lost to follow-up and 6 (2.3%) had follow-up less than two years. Left for analysis were 109 females and 106 males with a mean age of 32.9 years.
     Embolic materials used were N-butyl-2-cyanoacrylate in 66.0%, coils in 11.2% and silk in 1.9% of the cases. The mean volume of the nidus at the time of GKS was 4.7 cc (range 0.1–29.4 cc). The mean prescription dose was 19.6 Gy (range 4–28 Gy). The results were compared to 729 patients who underwent GKS alone.
     Of 215 patients who underwent both procedures angiography visualized no nidus in 71 patients (33%) after a mean follow-up of 3.5 years (range 0.6–11 years) while of 729 patients without embolization obliteration occurred after a mean of 3.3 years (range 0.6–15.3 years) in 444 patients (60.9%) (p < 0.001). The annual hemorrhage rate following GKS was 2% in both groups. Radiation induced changes on the MRI occurred in 43.7% of the embolized patients while in 33.4% of the non-embolized patients (p = 0.028). Permanent neurologic deficits associated with radiation induced changes were observed in 2.7% of the embolized patients versus 1.3% in the non-embolized patients (p = 0.14).
     This is a retrospective study.
     The obliteration rate is significantly lower and the occurrence of radiation induced changes is higher in the embolized versus non-embolized AVMs. The weakness of the present study is that the conclusions are derived from a patient material referred from 56 countries of 5 continents over a period of 20 years. Death or movement of patients and retirement or death of referring doctors resulted occasionally in unsatisfactory follow-up information.
     Shifting quality of logistics and experience in development during the early stages of the project may partially explain the meager results. To improve the outcomes of the combined management strict indication criteria should be developed. The endovascular specialist should be cautious in the selection of cases and embolize only AVMs where there are realistic chances of significant reduction of the nidus to a compact target.


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