An abnormal bony growth.

The space between the lower two meningeal layers closest to the brain, containing the cerebrospinal fluid.

The glucose and sodium-rich, potassium-poor tissue fluid of the brain and spinal cord. The fluid supplies nutrients and removes waste products; it is also a watery cushion that absorbs mechanical shock to the central nervous system.

A condition classified as severe, but of short duration.

Forced out of position. 

 A complex vascular network located at the base of the brain. It is formed by the following interconnected arteries: internal carotid, anterior cerebral, posterior cerebral, basilar, anterior communicating, and posterior communicating.

A section of bone removed from the skull during craniotomy procedures.

A collection of blood vessels with abnormal communication between the arteries and veins. It may be the result of injury, infection, or a congenital condition.(include the medical abbreviation)

The pressure within the skull exerted by the brain tissue, blood, and cerebrospinal fluid. (include the medical abbreviation)

A rotating tool to cut tissue, e.g, to shave fatty deposits from arteries or remove the bone.