An innate or acquired dilation of blood vessels in the brain, known as an aneurysm, often only becomes apparent years later, unexpectedly manifesting as a brain hemorrhage that can trigger unbearable headaches, loss of consciousness, and ultimately a coma within seconds. Approximately 80,000 citizens in Germany experience such a life-threatening subarachnoid hemorrhage each year. This book provides an overview of brain hemorrhages caused by aneurysms and their treatment.