Topics

Topic

design image
Posterior communicating artery

The Posterior Communicating Artery (PCOM) is a critical component of the cerebral circulation, forming part of the Circle of Willis at the base of the brain. It connects the internal carotid artery system anteriorly with the posterior cerebral artery system, providing an essential collateral pathway for blood flow between the anterior and posterior cerebral circulations. This vessel plays a significant role in maintaining cerebral perfusion, especially in cases of arterial stenosis or occlusion.

Synonyms

  • PCOM

  • Posterior communicating branch

  • Communicating branch of the posterior cerebral artery (less common)

  • Arteria communicans posterior (Latin)

Origin and Course

  • Origin: Arises from the internal carotid artery (ICA), specifically at its supraclinoid segment (distal to the origin of the ophthalmic artery).

  • Course:

    • Courses posteriorly and slightly medially from its origin.

    • Runs above the oculomotor nerve (cranial nerve III).

    • Travels toward the posterior cerebral artery (PCA), specifically joining its P1 segment.

    • Contributes to the anastomotic Circle of Willis, linking the anterior (carotid) and posterior (vertebrobasilar) circulations.

  • Relations:

    • Medial to the uncus of the temporal lobe.

    • Superior to the posterior perforated substance.

    • Near structures such as the optic tract and the hypothalamus.

Function

  • Acts as a collateral vessel, allowing compensation in cases of stenosis or occlusion of either anterior or posterior circulations.

  • Maintains perfusion to critical brain regions if a primary vessel is compromised.

  • May provide the primary supply to the PCA (fetal-type configuration) in some individuals.

  • Supplies small perforating branches to the hypothalamus, thalamus, and optic tract.

MRI Appearance

  • Normal Vessel: Appears as a small, flow void or tubular structure on T2-weighted images.

  • MR Angiography (MRA):

    • Visualized as a thin vessel connecting the supraclinoid ICA to the PCA.

    • Often smaller than the anterior communicating artery.

    • May appear prominent in fetal-type configuration.

  • Pathology:

    • Aneurysms at the PCOM origin are common and can be visualized as flow voids or signal intensity changes.

    • Infarcts in the PCOM territory may involve the thalamus or optic tract.

CT Appearance

  • Non-contrast CT:

    • Not usually directly visible due to small size.

    • Acute hemorrhage related to PCOM aneurysm rupture may be seen in the subarachnoid space.

  • CT Angiography (CTA):

    • Visualized as a small vessel connecting the ICA and PCA.

    • Can detect aneurysms, vessel caliber, and anatomical variants.

  • Calcifications or aneurysms:

    • Aneurysms may appear as round, hyperdense structures at the ICA-PCOM junction.

    • Calcified vessel walls or aneurysms may be identified.

MRI images

Posterior communicating artery axial t2 3T MRI image

MRI images

Posterior communicating artery axial TOF image

CT image

Posterior communicating artery ct images