Real-Time Stereotactic MRI-Guided Sclerotherapy with Bleomycin-Polidocanol Foam: Illuminating Inaccessible Venous Malformations.

Objectives: Venous malformations (VMs) that infiltrate the muscular layer, involve or are closely adjacent to critical nerves or vessels, or are located deep within or very close to major organs in the thoracic or abdominal cavities are challenging to access during sclerotherapy, which we defined as inaccessible VMs. This study proposed an integrated real-time stereotactic MRI-guided sclerotherapy with bleomycin-polidocanol foam (RSMS-BPF) for the treatment of inaccessible VMs, focusing on its clinical feasibility, efficacy, and safety. Methods: A retrospective study was conducted involving patients treated with RSMS-BPF between 2019 and 2021. During the sclerotherapy, the intraoperative magnetic resonance imaging (MRI) was combined with an optical navigation system to guide precise needle placement and track BPF, a foam sclerosant optimized for MRI visibility. Radiological response was assessed by lesion volume, while clinical improvement was evaluated through patients' description of their symptoms. Rigorous follow-up and documentation of complications were conducted. Results: A total of 42 patients (mean age 23.6 ± 1.6 years; 18 males) were treated in 64 sclerotherapy sessions. The treatment achieved an overall response rate of 89.5%. Imaging analysis revealed an average lesion volume reduction of 59.6%. 57.9% of patients achieved good or excellent radiological responses. After a median follow-up of 12.25 months, 60.53% of patients reported complete or significant relief. Lesion depth did not affect treatment efficacy (p = 0.43). Minor complications included skin hyperpigmentation (5.3%, 2/38) and blisters (2.6%, 1/38), with no major complications observed. Conclusions: RSMS-BPF demonstrated satisfactory efficacy and safety in VMs treatment, particularly for inaccessible VM lesions. It enables authentic real-time dynamic tracking during sclerotherapy, achieving unparalleled precision targeting while minimizing procedural risks. These findings strongly support routine integration of RSMS-BPF as first-line therapy for complex vascular malformations with critical anatomical constraints.