The cranial vault in an adult is an enclosed space encased by the rigid skull. The Monro–Kellie doctrine proposed in the early nineteenth century states that the volume inside the cranium is fixed and normally filled with the brain, cerebral spinal fluid, and blood in a state of equilibrium. An increase in the volume of one of these constituents must be compensated by a decrease in another. Intracranial pressure (ICP) is the pressure inside the skull due to the volume within the cranium. Elevated ICP can be severely debilitating and even life-threatening. It is very important to quickly identify signs and symptoms of elevated ICP, diagnose the pathology, and promptly initiate treatment in the emergency setting to prevent irreparable brain damage, significant disability, or death.

Neuro-oncologic emergencies encompass a wide variety of complaints and can occur in patients with both CNS and non-CNS malignancies. The differential diagnosis for neurologic symptoms includes brain metastases, primary brain tumor, leptomeningeal disease, spinal cord compression, infection, and neurologic complications of cancer. The emergency physician must consider CNS tumors in their initial differential diagnosis of common chief complaints (e.g., headache, seizure, weakness), and deal with CNS emergencies in patients with established cancer diagnoses.