An External Ventricular Drain (EVD) is a medical device used to manage increased intracranial pressure by draining excess cerebrospinal fluid (CSF) from the brain's ventricles. It consists of a catheter inserted into the ventricles, connected to a drainage system that allows for monitoring and control of fluid levels. EVDs are commonly used in patients with conditions such as hydrocephalus, traumatic brain injury, or subarachnoid hemorrhage. The procedure is typically performed in a hospital setting, and careful monitoring is essential to prevent complications like infection or bleeding.