Abstract: Bihemispheric anterior cerebral artery is a rare vascular variant that can affect cerebral blood flow distribution and increase the difficulty in diagnosing ischemic events. This article reports a case of TIA presenting with recurrent alternating unilateral lower limb weakness as the primary manifestation. Imaging examinations revealed hypoplasia of the right A1 segment of the anterior cerebral artery, severe stenosis of the left A2 segment, and the presence of a bihemispheric anterior cerebral artery variant; brain CTP indicated hypoperfusion in the bilateral anterior cerebral artery territories. After comprehensive evaluation, the patient received intravenous thrombolysis and intensive antiplatelet therapy, with no recurrence observed during follow-up. Multimodal imaging suggested that the clinical manifestations were closely related to hemodynamic abnormalities associated with hypoperfusion. This case suggests that in patients presenting with alternating unilateral lower limb weakness, vigilance is required regarding cerebrovascular variants and hypoperfusion mechanisms, and multimodal imaging examinations should be considered when necessary to improve diagnostic accuracy.

Key words: Bihemispheric anterior cerebral artery; Vascular variation; Transient ischemic attack

摘要： 双半球分支大脑前动脉是一种罕见的血管变异，可影响脑血流分布并增加缺血事件的诊断难度。本文报道1例以反复发作的交替性单侧下肢无力为主要表现的TIA患者。影像学检查显示右侧大脑前动脉A1段纤细，左侧大脑前动脉A2段重度狭窄，并存在双半球分支大脑前动脉变异；头颅CTP提示双侧大脑前动脉供血区低灌注。经综合评估后给予静脉溶栓及强化抗栓等治疗，患者症状未再发作。多模态影像提示其临床表现与低灌注相关的血流动力学异常密切相关。本病例提示，对于表现为交替性单侧下肢无力的患者，应警惕脑血管变异及低灌注机制，必要时结合多模态影像学检查以提高诊断准确性。

关键词: 双半球分支大脑前动脉; 血管变异; 短暂性脑缺血发作