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Basilar artery

The Basilar artery is a critical blood vessel located at the base of the brain. It plays an essential role in supplying oxygenated blood to the posterior regions of the brain, including the brainstem, cerebellum, and parts of the occipital lobes. Formed by the union of the vertebral arteries, the basilar artery courses upward along the ventral surface of the pons, ultimately dividing into the posterior cerebral arteries. Its patency and integrity are vital for brainstem function, and pathology involving this artery can have severe neurological consequences.

Synonyms

  • Arteria basilaris (Latin)

  • Basilar trunk (less commonly used)

Origin and Course

  • Origin: Formed by the union of the right and left vertebral arteries at the lower border of the pons (pontomedullary junction).

  • Course:

    • Ascends in the midline on the ventral (anterior) surface of the pons within the prepontine cistern.

    • Runs upward and slightly forward.

    • Terminates at the upper border of the pons by bifurcating into the right and left posterior cerebral arteries.

    • Along its course, gives off several important branches:

      • Anterior inferior cerebellar arteries (AICA)

      • Pontine arteries

      • Superior cerebellar arteries

Function

  • Main arterial supply to the brainstem (pons and midbrain), cerebellum, and posterior cerebral hemispheres.

  • Supplies blood to:

    • Pons

    • Cerebellum (via AICA and superior cerebellar arteries)

    • Inner ear (via labyrinthine artery in some individuals)

    • Occipital lobes (via terminal branches—posterior cerebral arteries)

  • Essential for autonomic and cranial nerve functions mediated by brainstem structures.

MRI Appearance

  • Normal Basilar Artery:

    • Seen as a flow void (dark signal) on routine T1 and T2-weighted images due to rapidly flowing blood.

    • Best visualized on MR angiography (MRA) as a tubular, midline structure ascending along the pons.

    • Pathological findings: Loss of flow void (suggesting thrombosis), abnormal dilation (aneurysm), or stenosis.

  • Clinical Utility:

    • MRA and contrast-enhanced MRI can assess vessel patency, detect aneurysms, stenosis, dissection, or occlusion.

CT Appearance

  • Non-contrast CT:

    • The basilar artery is not directly visualized unless there is pathology (e.g., hyperdense basilar artery sign indicating acute thrombosis).

    • Occasionally, the artery can appear as a slightly hyperdense linear structure anterior to the pons.

  • CT Angiography (CTA):

    • Clearly delineates the basilar artery’s course, caliber, and branches.

    • Used to assess for aneurysm, stenosis, occlusion, and vascular malformations.

  • Pathological Signs:

    • Hyperdensity in the expected location (hyperdense basilar artery sign) suggests acute thrombus.

    • Absence or irregularity of contrast filling may indicate occlusion or stenosis on CTA.

MRI images

Basilar artery MRI T2 coronal 3t image

MRI images

Basilar artery MRI TOF axial image

CT images

Basilar artery CT image

CT image

Basilar artery