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

Background: Although the angioarchitecture of perimedullary arteriovenous fistulas (PMAVFs) is straightforward, their size and blood flow are highly heterogeneous. This study aimed to evaluate the differences in clinical features and outcomes of PMAVFs based on lesion size and blood flow.

Methods: 114 consecutive patients with PMAVFs from two institutes were retrospectively reviewed. The lesions were classified as either micro-PMAVFs (shunt point diameter <1 cm) or macro-PMAVFs (shunt point diameter ≥1 cm).

Results: 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.