A novel etiological classification in patients with intracranial large vessel occlusion and endovascular treatment: discordance with the classic and SSS TOAST systems: A retrospective cohort study

Purpose: Among patients with acute ischemic stroke (AIS), those with intracranial large vessel occlusion (LVO) should undertake endovascular treatment (EVT) based on mechanical thrombectomy. Although the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification system has been used in overall population of patients with AIS, especially for secondary prevention. In the current study, a new classification system for the LVO population is proposed.Methods: The classic TOAST and Stop Stroke Study TOAST (SSS TOAST) were applied to the LVO population. Based on discordance with those systems, a new LVO classification system was developed and applied to the LVO population. The new system comprised extracranial atherosclerosis (ECAS), intracranial atherosclerosis (ICAS), cardioembolism (CE), cryptogenic embolism, stroke of undetermined etiology (SUE; two or more etiologies), and stroke of other determined etiology (SOE) where small artery occlusion was removed.Results: The LVO classification system comprised 43 ECAS (6.52%), 141 ICAS (21.36%), 303 CE (45.91%), 75 cryptogenic embolism (11.36%), 75 SUE (11.36%; cardioembolic source in 98.67%), and 23 SOE (3.48%) patients. The ICAS group had a significantly longer median onset-to-puncture time than the other groups. In the ICAS group, 102 of 141 (72.34%) remained partial recanalization after EVT.Conclusion: The LVO classification system differentiating ECAS and ICAS in patients with large artery atherosclerosis and classifying cryptogenic embolism is more suitable for patients with EVT for intracranial LVO. Further studies for predicting underlying ICAS and planning treatment strategy should be performed.