Double posterior inferior cerebellar artery.

Posterior inferior cerebellar artery (PICA) is one of the cerebellar arteries which originates from the vertebral artery and has the most complex and variable course. It usually originates from the vertebral artery intracranially and as a single trunk; however, absent, double trunk, extracranial, and extradural PICA may exists although very rare. In a collection of 50 cerebellar specimens (100 hemispheres) injected with colored gelatin, we have encountered unilateral double PICA in 2 specimens. In both the cases (both male, aged 45 and 65 years) double trunks of PICA were observed on the right side. Double-trunk PICA may signal an improved blood supply to the corresponding cerebellar hemisphere; however, the second trunk, which may also be called an accessory trunk, is usually smaller than the first (main) trunk of PICA.