The cerebellar tonsils are encountered in many surgical corridors including approaches to the fourth ventricle, supra and subtonsillar, the median suboccipital and different surgical procedures for CMI. Hence, the knowledge of possible variations in the position of cerebellar tonsils is a basic prerequisite for a surgeon operating in this area and relevant vascular anatomy also assumes importance to avoid inadvertent injury to the anterior and posterior, inferior cerebellar arteries.

The Arnold chiari malformation Type 1(ACM I) is a congenital malformation, generally asymptomatic during infancy, often manifests with headaches and other cerebellar symptoms.