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Posterior inferior cerebellar artery

The posterior inferior cerebellar artery (PICA) is the largest branch of the vertebral artery, supplying blood to the posterior inferior portion of the cerebellum, the medulla oblongata, and the choroid plexus of the fourth ventricle. PICA originates from the vertebral artery just before it joins the basilar artery, looping around the medulla oblongata and following a curved, tortuous course along the cerebellar tonsils.

PICA is critical in maintaining posterior circulation of the brain, and its compromise can result in lateral medullary (Wallenberg) syndrome, cerebellar infarction, or hydrocephalus due to fourth ventricle involvement. The artery gives off several branches, including medullary, tonsillar, and cortical branches, which form anastomoses with the anterior inferior cerebellar artery (AICA) and superior cerebellar artery (SCA).

Function

  • Supplies posterior inferior cerebellum, including cerebellar hemispheres and vermis

  • Supplies lateral medulla oblongata and medullary nuclei

  • Vascularizes choroid plexus of the fourth ventricle

  • Forms collateral circulation with AICA and SCA to maintain cerebellar perfusion

Synonyms

  • PICA

  • Posteroinferior cerebellar artery

  • Vertebral artery branch to cerebellum

MRI Appearance

T1-weighted images:

  • On standard MRI, PICA is not directly visible due to its small caliber.

  • Flow voids may appear as linear hypointensities along its course in high-resolution sequences.

T2-weighted images:

  • Similarly, PICA appears as a flow void (dark linear structure) due to rapid arterial flow.

  • Surrounding cerebellar tissue shows normal signal; infarcts from PICA occlusion appear hyperintense on T2 and FLAIR sequences.

MRA (Magnetic Resonance Angiography):

  • PICA is clearly visualized as a tortuous, enhancing vessel originating from the vertebral artery.

  • Stenosis, aneurysm, or dissection appears as focal narrowing, dilation, or irregularity.

T1 Post-Contrast (Gadolinium-enhanced):

  • PICA can enhance as a linear vessel in high-resolution contrast-enhanced MR angiography sequences.

  • Pathology such as aneurysm, arteriovenous malformation, or vessel wall inflammation shows focal enhancement.

CT Appearance:

  • On non-contrast CT, PICA is generally not visible due to small size.

  • CT Angiography (CTA) shows PICA as a branch from the vertebral artery, with tortuous loops along the cerebellar tonsils.

MRI images

Posterior inferior cerebellar artery mri sag image -img-00000-00000

MRI images

Posterior inferior cerebellar artery