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Anterior Communicating Artery

The anterior communicating artery (ACom) is a short but critical midline artery that connects the left and right anterior cerebral arteries (ACA) at the level of the A1–A2 junction, forming part of the anterior circle of Willis. Its average length is about 1–3 mm, though variations in length, caliber, and duplication are common.

The ACom plays a vital role in collateral circulation between the two anterior cerebral arteries, maintaining cerebral perfusion when one ICA is compromised. It also gives rise to perforating branches that supply the hypothalamus, optic chiasm, subcallosal area, and anterior commissure.

Clinically, the ACom is the most frequent site of intracranial aneurysms, accounting for approximately 30–40% of all saccular aneurysms. Rupture leads to subarachnoid hemorrhage with severe morbidity and mortality. Precise imaging of the ACom and its variants is crucial for neurosurgical and endovascular planning.

Synonyms

  • ACom artery

  • Communicating artery of ACA

  • Anterior communicating segment of circle of Willis

Function

  • Provides anterior interhemispheric collateral circulation within the circle of Willis

  • Supplies perforating branches to hypothalamus, optic pathways, and basal forebrain

  • Serves as a frequent site of aneurysms with major clinical importance

MRI Appearance

T1-weighted images:

  • ACom appears as a tiny flow void (dark lumen) at the anterior interhemispheric fissure

  • Difficult to resolve without high-resolution sequences

T2-weighted images:

  • Vessel shows hypointense flow void

  • Pathology (aneurysm, thrombosis) may alter signal with surrounding hyperintensity if edema/ischemia present

FLAIR:

  • Vessel lumen not directly seen

  • Infarcts in ACom perforator territory (subcallosal area, hypothalamus) appear hyperintense

T1 Post-Gadolinium:

  • Enhances brightly along its short course between ACAs

  • Aneurysms appear as saccular enhancing outpouchings

MRA (Magnetic Resonance Angiography):

  • Flow-related enhancement makes the ACom appear as a bright linear/point-like connection between ACAs

  • Depicts ACom variants, hypoplasia, or duplication

  • Sensitivity is excellent for aneurysms >3 mm

CTA (CT Angiography):

  • Opacified with contrast, the ACom is seen as a bright, high-attenuation vascular channel between the ACAs

  • CTA is superior to MRA for detecting aneurysms, perforator branches, and vascular anomalies

  • 3D reconstructions demonstrate aneurysm neck, dome, and relation to adjacent arteries for surgical/endovascular planning

Anterior communicating artery MRI T2 axial image

Anterior communicating artery MRI T2 coronal image

Anterior communicating artery MRI T2 sagittal image

Anterior Communicating Artery (ACom) ct image