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Middle cerebral artery opercular segment (M3)

The M3 segment of the middle cerebral artery (MCA), also known as the opercular segment, begins after the artery emerges from the Sylvian fissure’s insular segment (M2) and courses laterally across the operculum. This segment follows the surface of the frontal, parietal, and temporal opercula before branching into cortical arteries that supply the lateral convexity of the cerebral hemispheres.

The M3 branches travel within the Sylvian fissure’s opercular portion, giving rise to arteries that supply the lateral frontal lobe, lateral parietal lobe, and superior temporal gyrus. It serves as a critical transition zone between insular (M2) arteries and cortical (M4) branches, and it participates in extensive anastomotic networks with anterior cerebral and posterior cerebral artery branches.

Synonyms

  • MCA M3 segment

  • Opercular MCA segment

  • Middle cerebral artery, opercular portion

Function

  • Supplies blood to the opercular regions of the frontal, parietal, and temporal lobes

  • Provides perfusion to language, motor, and sensory integration areas

  • Acts as a transitional vascular channel from deep Sylvian branches (M2) to cortical branches (M4)

  • Participates in collateral circulation through cortical anastomoses

MRI Appearance

T1-weighted images (non-contrast):

  • M3 branches appear as flow voids (signal loss) within the Sylvian fissure

  • Surrounded by intermediate signal cortical and subcortical parenchyma

T2-weighted images:

  • M3 arteries also demonstrate flow voids

  • Hyperintensity in adjacent cortex may suggest ischemia, edema, or gliosis

MRA (Magnetic Resonance Angiography):

  • TOF-MRA and contrast-enhanced MRA show the opercular course and branching pattern of M3

  • Normal M3 arteries appear as bright linear enhancing structures in the Sylvian fissure

  • Excellent for detecting stenosis, occlusion, aneurysms, or AVMs affecting opercular branches

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Enhances the lumen of M3 branches

  • Highlights vascular abnormalities and abnormal parenchymal enhancement due to vascular compromise

CT Appearance

Non-contrast CT:

  • M3 arteries are not directly visualized

  • Acute occlusion may present as a hyperdense MCA branch sign in the Sylvian fissure

CT Angiography (CTA):

  • Provides excellent visualization of the M3 segment course across the operculum

  • Clearly demonstrates branching into cortical arteries (M4)

  • Detects stenosis, occlusion, emboli, aneurysms, and arteriovenous malformations

  • CTA is essential in stroke imaging and neurosurgical planning

MRI images

Middle cerebral artery opercular segment (M3)