Incidence and Clinical Characteristics of Moyamoya Disease in Advanced Suzuki Disease Stages.

Moyamoya disease is a progressive steno-occlusive cerebrovascular disease. Intrinsically, its shifts the brain's vascular supply from the internal carotid to the external carotid system, known as internal-to-external carotid conversion, which is categorized by Suzuki's angiographic staging system. Although Suzuki's staging system remains the global standard for assessing longitudinal angiographic progression, the clinical characteristics of patients in the advanced stages, particularly in stage 6, are not well understood. Therefore, in this study, we investigated the incidence and clinical features in patients with moyamoya disease in advanced Suzuki stages. We retrospectively analyzed 280 hemispheres from 156 patients diagnosed with moyamoya disease through cerebral angiography between 1980 and 2023 at our institution. Angiographic features, including Suzuki disease stage and collateral pathways, were evaluated. Clinical outcomes, surgical indications, and postoperative courses were also assessed. Seventeen hemispheres (6.1%) were classified as Suzuki stage 5, and 6 hemispheres (2.1%) as stage 6, all in adult patients. Transdural collaterals, including ethmoidal and vault moyamoya vessels, were found in more than 80% of these advanced cases. Leptomeningeal collaterals from the posterior cerebral artery were frequently observed, whereas posterior cerebral artery stenosis was rare. Approximately half of the patients underwent revascularization surgery. No postoperative stroke recurrence was observed during the follow-up period of median 84 months. Suzuki stages 5 and 6 of moyamoya disease are rare; cases with stage 6 are particularly uncommon but show distinct angiographic features marked by internal-to-external carotid conversion and increased reliance on posterior circulation. Surgical revascularization is feasible and may be performed safely without stroke recurrence, even in patients with advanced disease stages.