title: What constitutes the M1 segment of the middle cerebral artery?
abstract: Intravenous tissue plasminogen activator has limited efficacy in fibrinolysis of large proximal intracranial thrombi. Thus, recent endovascular acute stroke trials restricted their selection criteria to patients with proximal occlusions in the anterior circulation. Although the terminal internal carotid artery occlusion is relatively easy to identify, there is often a debate as to what constitutes a proximal (involving the M1 segment) versus a distal (involving the M2 segment and beyond) middle cerebral artery occlusion. In light of overwhelming evidence demonstrating superiority of endovascular treatment in patients with proximal occlusion, this distinction has significant practical implications in patient selection. Here we present a brief review of the proximal (M1) segment of the middle cerebral artery anatomy and provide practical methods to recognize and separate the M1 and M2 segments. In keeping with the belief that CT angiography (CTA) (preferably multiphase CTA) is the ideal screening test for patients with emergent large vessel occlusion, we have provided tips for expeditious and accurate vascular imaging interpretation.
authors: Calgary Stroke Program, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors: Mayank
authors: M
authors: Goyal
authors: Calgary Stroke Program, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.|Department of Community Health Sciences, University of Calgary.
authors: Bijoy K
authors: BK
authors: Menon
authors: Divisions of Neuroradiology (Department of Medical Imaging), and Neurosurgery (Department of Surgery), Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada.
authors: Timo
authors: T
authors: Krings
authors: Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors: Shivanand
authors: S
authors: Patil
authors: Calgary Stroke Program, Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
authors: Emmad
authors: E
authors: Qazi
authors: Department of Diagnostic Imaging, Warren Alpert School of Medicine at Brown University, Providence, Rhode Island, USA.
authors: Ryan A
authors: RA
authors: McTaggart
authors: Department of Internal Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.
authors: Mohammed A
authors: MA
authors: Almekhlafi
authors: Reza
authors: R
authors: Jehan
authors: Division of Interventional Neuroradiology, Department of Radiology and Neurosurgery, University of California at Los Angeles, Los Angeles, California, USA.|Department of Neurology, University of California at Los Angeles, Los Angeles, California, USA.
authors: Jeffrey
authors: J
authors: Saver
authors: Department of Diagnostic Imaging, Warren Alpert School of Medicine at Brown University, Providence, Rhode Island, USA.
authors: Mahesh V
authors: MV
authors: Jayaraman
keywords: CT Angiography; Stroke; Thrombectomy