Microsurgical Anatomy of the Cerebellopontine Angle by the Retrosigmoid Approach

Abstract

Optimizing operative approaches to the cerebellopontine angle requires an understanding of the relationships of the cerebellar arteries, cranial nerves, brain stem, cerebellar peduncles, fissures between the cerebellum and brain stem, and the cerebellar surfaces. In this chapter, the microsurgical anatomy of the cerebellopontine angle by the retrosigmoid approach is presented. The CP angle is located between the superior and inferior limbs of the cerebellopontine fissure, a V-shaped angular cleft, formed by the cerebellum folding around the pons and middle cerebellar peduncle. When examining the anatomical relationships in the area, three neurovascular complexes are defined: an upper complex related to the superior cerebellar artery (SCA), a middle complex related to the anteroinferior cerebellar artery (AICA), and a lower complex related to the posteroinferior cerebellar artery (PICA). Other structures, in addition to the three cerebellar arteries, occurring in sets of three in the posterior fossa that bear a consistent relationship to the SCA, AICA, and PICA are the parts of the brain stem (midbrain, pons, and medulla); the cerebellar peduncles (superior, middle, and inferior); the fissures between the brain stem and the cerebellum (cerebellomesencephalic, cerebellopontine, and cerebellomedullary); and the surfaces of the cerebellum (tentorial, petrosal, and suboccipital). In addition, each neurovascular complex contains a group of cranial nerves.