Posterior inferior cerebellar artery (PICA)

Along with the AICA and SCA, the PICA is one of the principal vessels supplying the Cerebellum.

Anatomy

The PICA usually arises directly from the Arteria vertebralis. Typically, the PICA arises approximately 10 mm distal to the point where the vertebral artery becomes intradural and approximately 15 mm proximal to the vertebrobasilar junction[^1]. In approximately 5–8 % of cases, the PICA has an extradural origin[^1]. Another anatomical variant is the AICA-PICA, in which the PICA arises from the Arteria basilaris at the same location as the AICA. On angiography, the PICA demonstrates a cranial and caudal loop as well as the choroidal point. The PICA can be divided into five different segments[^4]:

• Anterior medullary: From the origin of the PICA to the inferior aspect of the olive. Gives rise to 1 to 2 short medullary branches supplying the ventral medulla oblongata.

• Lateral medullary: To the origin of cranial nerves IX, X & XI. Up to 5 perforators supplying the Brainstem.

• Tonsillomedullary: To the tonsillar midpoint. Includes the caudal loop on angiography.

• Telovelotonsillary (supratonsillar): Ascends in the tonsillomedullary fissure. Includes the cranial loop on angiography.

• Cortical segments

The first three segments must be preserved during a surgical procedure. The final two segments can be occluded with minimal deficits[^5].

Figure

Imaging

Clinical relevance

Aneurysms

Aneurysms of the PICA account for 0.49 to 3 % of all cerebral aneurysms [^1] [^6].

Hemifacial spasm

In patients with Hemifacial spasm, the PICA is frequently the vessel responsible for the neurovascular conflict.

Deficits

Occlusion of the PICA proximal to the choroidal point in the cranial loop carries a high risk of causing a medullary syndrome (e.g. Wallenberg syndrome), as numerous medullary perforators arise proximal to this point[^3].