A 49-year-old man presented with episodic headache lasting 30 to 60 minutes and relieved by resting. He is a chronic smoker with an unremarkable past medical history. The physical exam was normal. Computed tomography angiogram (CTA) found suspected aneurysmal dilation (white arrow) at the A1 segment of the right anterior cerebral artery (ACA), the left A2 segment of the left ACA supplied by the right ACA through the anterior communicating artery, and the A1 segment of left ACA absent (Fig 1A). Diagnostic cerebral angiography was performed for further evaluation. Right carotid angiography showed small outpouching at the right A1 segment, corresponding to the CTA finding. A three-dimensional rotational angiography showed that the small outpouching was the left accessory middle cerebral artery (MCA) infundibulum instead of a genuine aneurysm. A small branch from its apex crossed the middle line, ran laterally to the left Sylvian fissure, and terminated at the prefrontal area of the left hemisphere, suggestive of a left accessory MCA (white arrowheads) (Fig 1B, Video S1). After supportive medical treatment, the patient's headache subsided. The accessory MCA is an uncommon anomaly of the MCA that arises from the ACA and passes into the Sylvian fissure along the MCA.1 The incidence of accessory MCA in angiographic and anatomical studies is reported to be 0.3 to 4.0%, and that of duplicated MCA is 0.2 to 2.9%.2 A previous study by Komiyama et al2 reported a consistent cortical supply by the accessory MCA to the anterior frontal lobe. Previous literature reported that the accessory MCA arises from the ipsilateral ACA. Infundibular dilation is funnel-shaped widening at the origin of a cerebral artery. A small perforator or cortical artery arising from its apex is crucial to differentiate from the aneurysm. This case showed an infundibulum over a rare anatomical variant of the accessory MCA, originating from the contralateral A1 segment of ACA. Such anatomical variant was not reported in previous literature. This case illustrated the importance of identifying vascular anomalies with operative or endovascular management implications. We thank the patient for providing permission to share his information. W.L. and N.M. contributed to the study concept and design; W.L., N.M., and X.T. contributed to data acquisition and analysis: W.L., N.M., B.Y. contributed to drafting the manuscript and preparing the figure and video. Nothing to report. Obtained. The data that supports the findings of this study are available in the supplementary material of this article. Video S1. On three-dimensional rotational angiography, a small outpouching was detected at the A1 segment of the right anterior cerebral artery. A small branch from its apex crossed the middle line, ran laterally to the left Sylvian fissure, and terminated at the prefrontal area of the left hemisphere, suggestive of a left accessory middle cerebral artery. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Wai Ting Lui

Tao Xiong

Bo Yang

Ning Ma

Annals of Neurology

《神经病学年鉴》发表了对神经病学具有广泛兴趣的文章，尤其是那些对理解人类神经系统疾病的机制和治疗有重大影响的文章。尽管 ANNALS 使用多种临床和基本神经科学方法发表论文，但我们最感兴趣的是学术神经学家普遍感兴趣的那些手稿，包括临床试验和其他为医学实践提供信息的大规模研究。纯粹的基础研究，没有很强的临床或转化潜力，不太可能有足够的优先发表权。

The Annals of Neurology publishes articles on a wide range of topics relevant to neurology, particularly those that have a significant impact on understanding the mechanisms and treatments of human neurological diseases. While the Annals employs various clinical and basic neuroscience methods for publication, we are particularly interested in manuscripts that are of general interest to academic neurologists, including clinical trials and large-scale studies that provide valuable information for medical practice. Purely basic research, lacking strong clinical or translational potential, is less likely to receive priority for publication.

《Annals of Neurology》发表了与神经病学相关的广泛主题文章，特别是那些对理解人类神经系统疾病的机制和治疗具有重要影响的研究。虽然《Annals of Neurology》采用多种临床和基础神经科学方法来发表论文，但我们特别关注那些学术神经学家普遍感兴趣的稿件，包括临床试验和其他为医学实践提供重要信息的大规模研究。纯粹的基础研究，若缺乏明显的临床或转化潜力，通常不具备优先发表的条件。

Category	Quartile
医学	1
医学, 临床神经病学	1
医学, 神经科学	1

Infundibulum of an Aberrant Accessory MCA Mimics Aneurysm

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