Updated classification with spinal dysraphism and treatment outcomes of arteriovenous shunts below conus: a retrospective cohort study

Background Arteriovenous shunts below conus medullaris (AVS-BC) are understudied, particularly those associated with spinal dysraphism. This study aimed to refine the classification and management of AVS-BC. Methods A retrospective analysis of patients with AVS-BC from two centers over two decades was performed, focusing on clinical presentations, angioarchitecture, and treatment outcomes. AVS-BC was classified into eight subtypes based on angioarchitecture, dural relation, and spinal dysraphism presence. Treatment efficacy was evaluated using changes in the modified Aminoff and Logue’s Scale and the modified Denis Pain and Numbness Scale. Results The cohort included 140 patients (85.0% male) with a median onset age of 54 years (IQR 47–62). Spinal dural arteriovenous fistula was the most prevalent subtype (32.1%). AVS-lipoma (58.8%) and AVS with spina bifida/meningocele (75.0%) were mainly located in S3–S5, while others were above S2 (p<0.001). Most AVS-BCs were supplied by the internal iliac artery (37.1%) and drained intradurally (96.4%). Venous lakes were common in spinal epidural arteriovenous fistula (88.2%) and paravertebral arteriovenous fistula (100.0%). Larger drainage veins (>2.0 mm) were found in paravertebral arteriovenous fistula (PVAVF) (50.0%) and AVS with spina bifida/meningocele (AVS-SBD) (50.0%) (p=0.012). Embolization was the preferred treatment (50.7%), achieving a 97.1% anatomical cure rate. Despite functional improvements, 25% experienced deterioration during a median follow-up of 47 months (IQR 20–113). Conclusions The refined AVS-BC classification revealed significant angioarchitectural variations. Tailored treatment strategies, especially embolization, resulted in high anatomical cure rates, though post-treatment deterioration warrants further investigation.