Posterior inferior cerebellar artery

Dr Craig Hacking and A.Prof Frank Gaillard et al.

Posterior inferior cerebellar artery (PICA) is one of the three vessels that provide arterial supply to the cerebellum. It is the most variable and tortuous cerebellar artery.

Its origin is highly variable:

  • ~20% arise extracranially, inferior to the foramen magnum
  • 10% arise from the basilar rather than vertebral artery
  • 2% bilaterally absent
  • occasionally loops around the cerebellar tonsil
  • anterior medullary segment
    • from its origin around the inferior aspect of the olive of the medulla
  • lateral medullary segment
    • curves forming the 'caudal loop' which is located anteroinferior to the tip of the cerebellar tonsil, but does not relate to the tonsilar position
    • the apex of the loop is
      • above foramen magnum in 60% of cases
      • at the level of foramen magnum in 10%
      • and below in 30%
    • its relationship to the vertebral artery is also variable, 84% lateral and 16% medial
  • posterior medullary segment
  • supratonsillar segment
    • junction between the posterior medullary segment and the supratonsillar segment is upwardly convex and is the site of origin of small choroidal branches: it is known as the "choroid point" - this point has a constant relationship with the 4th ventricle and was used prior to cross-sectional imaging to assess for shift in its position
  • anterior and lateral medullary segments
    • small perforating medullary branches (absent in 50%)
  • supratonsillar segment
    • tonsillohemispheric branch
    • inferior vermian branch

Note: occasionally a small vertebral will terminate into a common PICA/AICA trunk.

Has a variable territory depending on the size of the AICA (AICA-PICA dominance). Typically it suppies:

  • posteroinferior cerebellar hemispheres (up to the great horizontal fissure)
    • cerebellar tonsils: 85% of the time
    • biventral lobule: 80%
    • nucleus gracilis: 85%
    • superior semilunar lobule: 50%
  • inferior portion of the vermis
  • lower part of the medulla: 50%
  • inferior cerebellar peduncles
Anatomy: Brain
Anatomy: Spine
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Article information

rID: 5015
Section: Anatomy
Synonyms or Alternate Spellings:
  • Posterior inferior cerebellar artery (PICA)
  • PICA

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Cases and figures

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    Figure 1: posterior fossa vascular territories
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    PICA infarct
    Case 1: left PICA infarct
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    Figure 2: mid-cerebellum
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    Case 2: right PICA infarct - DWI
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    Figure 3: inferior cerebellum
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    Case 3: PICA aneurysm
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    Figure 4: showing caudal loop and choroid point
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    Figure 5: PICA origin on lateral angiogram
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    Figure 7: normal COW anatomy
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