Natural History of Metameric Spinal Cord Arteriovenous Malformations

Spinal arteriovenous metameric syndrome (SAMS) is a rare form of spinal cord arteriovenous malformations with a metameric distribution affecting the spinal cord and related structures derived from the same embryological segment. Its natural history and impact on clinical outcomes, compared with nonmetameric spinal cord arteriovenous malformations, remain unclear.

This retrospective, single-center study included 253 patients with intradural spinal cord arteriovenous malformations between 2002 and 2024, that have either not been considered for embolization or followed up during the period before embolization. This study aimed to evaluate the natural history of SAMS and identify the risk factors for clinical worsening, hemorrhagic events, and angiographic worsening during observation. A stratified log-rank test and Cox proportional hazards model were used to estimate hazard ratios (HRs) and 95% CI.

In the overall population, the median age of onset was 24 years, females accounted for 130 patients (51.3%), and the median observational period was 19 months. This cohort included 71 patients with SAMS and 182 without SAMS. The 10-year cumulative rates of clinical worsening were 27.0% in the metameric and 18.0% in the nonmetameric group. The risk of clinical worsening and hemorrhagic events did not show statistically significant differences between the 2 groups (HR, 1.71 [95% CI, 0.83-3.54]; P=0.137 and HR, 1.65 [95% CI, 0.75-3.61]; P=0.199). The metameric group with hemorrhagic onset had the highest risk of experiencing hemorrhagic events compared with the nonmetameric group without hemorrhagic onset (HR, 4.87 [95% CI, 1.35-17.53]; P=0.015). The metameric group exhibited significantly higher rates of angiographic worsening compared with the nonmetameric group (HR, 11.37 [95% CI, 1.32-97.78]; P=0.005). The presence of nonspinal cord-associated metameric lesions did not significantly affect the natural history of SAMS.

SAMS had higher angiographic worsening than non-SAMS. Hemorrhagic onset in SAMS was an independent predictor of rebleeding during observation, without any influence of nonspinal cord-associated metameric lesions. Close radiological follow-up and early intervention, particularly for hemorrhagic-onset cases, may be necessary to improve outcomes.