Clinical features and outcomes of perimedullary arteriovenous fistulas: comparison between micro- and macro-type lesions.

The patients with micro-PMAVFs were older at the first presentation (33.50 vs 13.50 years, p<0.001). Macro-PMAVFs were more commonly associated with spinal metameric arteriovenous shunts (6.9% vs 28.6%, p=0.003). Compared with the macro-PMAVFs, the micro-PMAVFs showed a significantly higher risk of gradual clinical deterioration after initial onset (73.6%/year vs 10.0%/year; HR 3.888, 95% CI 1.802 to 8.390, p=0.001). A total of 58.6% of the micro-PMAVFs were treated surgically, whereas 85.7% of the macro-PMAVFs were treated via endovascular approaches. Complete obliteration was 73.7% for the whole cohort, and was more common for the micro-PMAVFs than for the macro-PMAVFs (87.9% vs 58.9%, p=0.001). At the last follow-up, spinal function was significantly improved compared with the pretreatment status, and the rate of severe disability of patients with macro-PMAVFs was slightly but not significantly higher than that of patients with micro-PMAVFs (16.1% vs 8.6%, p=0.315) CONCLUSIONS: The clinical risks, treatment strategies and obliteration rates of PMAVFs differ based on their size and blood flow.