What Causes Brain Swelling?

Brain swelling, also known as cerebral edema, and intracranial pressure (ICP) can be caused by over 300 conditions and diseases. Just as an ankle or knee will swell with injury or infection, so too will the brain. Brain swelling is a very serious condition, for it leads to compression of the brain tissue, eventually leading to a loss of function with in the brain.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Head Trauma/Concussion

The brain is doubly protected by the body, first with the hard layer of bone and second with a layer of cerebrospinal fluid (CSF). The brain essentially floats inside the skull in the CSF. This fluid circulates in and around the brain and provides not only nutrients but shock absorption for the brain tissue. The fluid helps slow down the movement of the brain within the skull. Injuries that are too fast or too violent, like direct head trauma or a severe car accident, will cause the brain to bump into the skull and cause a bruise or even bleeding. This bump can be mild, causing only a temporary loss of function and little swelling or it could be more severe as in surgeons having to remove part of the skull to allow room for the brain to swell and fluid to drain out.


This is a condition in which the CSF production is too high or cannot reach the brain tissues due to other fluids, like blood, being in the way. The CSF flows through channels in the brain called ventricles. If the fluid cannot circulate properly it will start to build up in the ventricles deep inside the brain; this causes swelling from inside the brain and starts to compress on the tissues. Many diseases and conditions can cause hydrocephalus. Another term for this is “water on the brain.”


Certain types of bacteria, viruses and parasites can cause the brain or parts around the brain to swell. The brain has a coating around it called the meninges, which is composed of three layers. The meninges help with nutrient and blood supply to the brain as well as encases the brain matter, much like skin encases the body. Certain viruses and bacteria, mainly bacteria, can infect the meninges and cause them to swell. Since this tissue surrounds the brain, it will compress the brain matter and cause the brain to swell. This type of infection is called meningitis. When the brain tissue itself swells from infection it is called encephalitis. Most of these infections are caused by outside sources like rabid animal bites and affect those with weakened immune systems.


Stroke as defined by the American Academy of Orthopaedic Surgeons is a sudden interruption of blood flow to the brain resulting in the loss of brain function 1. A stroke can be caused by a blood vessel bursting open and bleeding into the surrounding area or by a blood vessel being blocked. Either form of stroke will cause the brain to swell and cause noticeable deficits in movement, speech and general function.