Figure 3.1. Positioning and craniotomy. (a) The operation begins with the proper positioning of the patient, so that the surgeon can perform the operation in a relaxed and comfortable manner. The patient should be placed in a position that minimizes pressure points, facilitates venous outflow to minimize congestion, and enables the surgeon to obtain many working trajectories by simply turning the bed. For an extreme-lateral supracerebellar infratentorial approach, for example, the patient is positioned with the head turned to the contralateral side, the chin tucked, and the neck slightly extended (arrow) toward the floor to enable gravity-dependent retraction of the cerebellar hemisphere and a more generous working space for the surgeon to perform the operation. (b) The proper placement of a craniotomy provides adequate exposure to deep structures without unnecessary exposure of the adjacent brain or vessels. For a retrosigmoid craniotomy, for example, the craniotomy should be placed to expose the transverse–sigmoid junction to enable the surgeon to obtain a flat view of the petrous ridge while being able to dynamically retract the exposed sinus edge. (c) Failure to expose the junction, such as by leaving bone over the sinus, hinders the approach to the cerebellopontine angle, resulting in the need for more cerebellar retraction to obtain similar exposure. Careful attention to craniotomy positioning significantly decreases morbidity without sacrificing the working space necessary to successfully perform an operation on the brainstem. Note that the contents of the cerebellopontine angle are well visualized using the craniotomy in (b), where the transverse–sigmoid junction is mobilized.