Cerebral edema is excess accumulation of fluid (edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compression of brain tissue and blood vessels. Symptoms vary based on the location and extent of edema and generally include headaches, nausea, vomiting, seizures, drowsiness, visual disturbances, dizziness, and in severe cases, coma and death.

Cerebral edema is commonly seen in a variety of brain injuries including ischemic stroke, subarachnoid hemorrhage, traumatic brain injury, subdural, epidural, or intracerebral hematoma, hydrocephalus, brain cancer, brain infections, low blood sodium levels, high altitude, and acute liver failure. Diagnosis is based on symptoms and physical examination findings and confirmed by serial neuroimaging (computed tomography scans and magnetic resonance imaging).

The treatment of cerebral edema depends on the cause and includes monitoring of the person's airway and intracranial pressure, proper positioning, controlled hyperventilation, medications, fluid management, steroids. Extensive cerebral edema can also be treated surgically with a decompressive craniectomy. Cerebral edema is a major cause of brain damage and contributes significantly to the mortality of ischemic strokes and traumatic brain injuries.

As cerebral edema is present with many common cerebral pathologies, the epidemiology of the disease is not easily defined. The incidence of this disorder should be considered in terms of its potential causes and is present in most cases of traumatic brain injury, central nervous system tumors, brain ischemia, and intracerebral hemorrhage. For example, malignant brain edema was present in roughly 31% of people with ischemic strokes within 30 days after onset.