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Vasospasm: Exaggerated, persistent contraction of the walls of a blood vessel.

Vegetative State: A condition in which patients are unconscious and unaware of their surroundings, but continue to have a sleep/wake cycle and can have periods of alertness.

Ventilator: A machine that does the breathing work for the unresponsive patient. It delivers moistened (humidified) air with the appropriate percentage of oxygen and at the appropriate rate and pressure.

Ventricles: Open spaces or cavities in the brain which are filled with the same fluid that surrounds the brain and spinal cord.

Ventriculostomy: A surgical procedure that drains cerebrospinal fluid from the brain by creating an opening in one of the small cavities called ventricles.

Vestibular: System in the middle of the ear which senses movement. Injury can lead to dizziness.