Bilateral Extradural Posterior Inferior Cerebellar Artery Origins Where Vertebral Artery Ascends Between Transverse Foramina of C-2 and C-1, with Simultaneous Right Double Origin PICA: Rare Case Report and Literature Review.

BACKGROUND: The location of the origin of the posterior inferior cerebellar artery (PICA) is highly variable. An extracranial origin PICA from the vertebral artery (VA) is not rare. But the PICA originated extradurally where the VA ascends between the transverse foramina of C-2 and C-1, a rare anatomic variant. Double-origin PICA is another rare anatomic variant observed in 1%-4% of patients in whom 2 PICA branches converge distally.

CASE DESCRIPTION: We present a rare cadaveric anatomy case in which both PICAs originated extradurally between the vertebrae C1 and C2, a simultaneously existing right double-origin PICA. For this case, the right PICA was a double-origin PICA, including 1 extradural origin in which the VA ascends between the transverse foramina of C-2 and C-1 and another being intradural and intracranial.

CONCLUSIONS: To our knowledge, this is the first report of a cadaveric anatomy case of bilateral PICA that originated extradurally between the vertebrae C-1 and C-2, and simultaneously there existed a right double-origin PICA. Such a case is rare, but understanding of the anatomic variation is important. To avoid complications during surgery at the craniovertebral junction, these potential variations should be correctly identified preoperatively.