Anatomy of the posterior inferior cerebellar artery: relevance for C1-C2 puncture procedures.

Lateral C1-C2 puncture is associated with a number of complications including damage of aberrant posterior inferior cerebellar arteries (PICA). We propose to determine the frequency of cases in which the PICA originates or descends below C1, thus posing a risk to the patient undergoing lateral C1-C2 puncture. Two hundred and eleven consecutive patients who received bilateral or unilateral vertebral angiography for evaluation of cerebrovascular lesions were included in this study. In total, 346 PICAs were studied. Lateral vertebral angiograms were analyzed for the location of the origin of the PICA and the inferior-most portion of the PICA relative to three anatomical regions. Region 1 was defined as the region above the foramen magnum. Region 2 was defined as the region below the foramen magnum but above the inferior border of the posterior arch of C1. Region 3 was defined as the region below the inferior border of the posterior arch of C1. In 2 of 346 angiograms (0.6%) and 2 of 211 patients (0.9%), the caudal loop of the PICA descended to Region 3. The PICA did not originate in Region 3 in any cases. In approximately 1% of patients in our study, the caudal loop of the PICA descended into a region that may have placed it at risk for damage during C1-C2 puncture. Our study suggests that it may be important for radiologists to assess the arterial anatomy of the C1-C2 region before performing C1-C2 puncture.