The posterior inferior cerebellar arteries. Some quantitative observations in posterior cranial fossa tumours and the Arnold-Chiari malformation

The radiological anatomy of the normal posterior inferior cerebellar artery is described. Measurements are made in the lateral and antero-posterior projections, of the position of the apex of the cranial loop of the posterior inferior cerebellar artery in fifty normal cases. The position of the caudal loop of the vessel in relation to the foramen magnum is also noted in the fifty normal cases. Vertebral angiograms on a series of sixty patients with posterior cranial fossa lesions, including three cases of the Arnold-Chiari malformation are reviewed. The tumour cases are divided into five sub-groups with reference to their situation in the posterior cranial fossa. Measurements made on the position of the cranial loop of the posterior inferior artery show that different types and different degrees of displacement of this segment of the artery occur for each of the five sub-groups of posterior fossa tumours. Factors possibly influencing these variations are discussed. The frequency of bilateral filling of the posterior inferior cerebellar arteries and radiological evidence of cerebellar tonsilar herniation are noted and discussed.