Impact of Embolization on Clinical Outcomes After Treatment of Metameric and Sporadic Spinal Cord Arteriovenous Malformations: An Analysis of 216 Patients

BACKGROUND AND OBJECTIVES: Spinal arteriovenous metameric syndrome (SAMS) is a rare, complex vascular disorder characterized by multifocal spinal cord arteriovenous malformations (SCAVMs) affecting structures derived from the same metameric segment. The long-term clinical outcome of SAMS, particularly after embolization, remains poorly understood. This study evaluated the clinical outcomes of embolization for SAMS compared with nonmetameric SCAVMs. METHODS: This retrospective study included 216 patients with intradural SCAVMs who underwent embolization (62 patients with SAMS and 154 patients without metameric background [non-SAMS group]). Clinical and imaging data were reviewed to assess clinical worsening, hemorrhagic events, and angiographic worsening during the observation period after initial embolization. RESULTS: The overall median observation period was 44 months (IQR, 1-307). The SAMS group was associated with a higher risk of clinical and angiographic worsening compared with the non-SAMS group (hazard ratio [HR] 2.90; 95% CI 1.37-6.12; P = .0003, and HR 5.04; 95% CI 2.03-12.50; P = .0001). Regarding hemorrhagic events, the SAMS group demonstrated a risk equivalent to the non-SAMS group (HR 1.93; 95% CI 0.65-5.78; P = .234). In subgroup analysis based on final occlusion rate (≥75% or <75%) of intradural SCAVMs, failure to achieve ≥75% occlusion in the SAMS group resulted in significantly worse clinical and angiographic outcomes (HR 5.28; 95% CI 1.90-14.66; P = .001, and HR 9.41; 95% CI 3.02-29.34; P = .0001). Achieving ≥75% occlusion resulted in a risk comparable with that of the non-SAMS group. CONCLUSION: Embolization reduced the risk of hemorrhagic events in SAMS to a level comparable with the non-SAMS group. However, SAMS carries a higher risk of clinical and angiographic worsening than non-SAMS, even after embolization. Achieving sufficient occlusion (≥75% occlusion) of intradural SCAVMs mitigates these clinical risks in SAMS.