Planning a keyhole neurosurgical intervention is challenging due to the complex brain anatomy and the risk of penetrating vital structures. This work presents a neurosurgical planning tool for safe and effective interventions in the brain by minimizing risk due to optimized access planning. The tool uses a modular architecture that allows integration of various risk structures, combined in a holistic model represented as volumetric risk maps. Risk evaluations are computed for linear and nonlinear trajectories and intuitively visualized as a projection onto the head surface. Neurosurgeons can choose between two separate modes for automatic access planning according to the type and complexity of the neurosurgical procedure. An evaluation with clinical experts demonstrates the practical relevance.