An external ventricular drain (EVD), also known as an extraventricular drain, an external ventricular catheter (EVC), or a ventriculostomy, is a medical device used to drain cerebrospinal fluid (CSF) from the brain’s ventricles.
EVDs are typically used in cases where there is increased intracranial pressure that needs to be relieved such as in hydrocephalus (excessive accumulation of CSF in the brain), traumatic brain injury, intraventricular haemorrhage, or certain neurological infections. The device allows for therapeutic CSF drainage and monitoring of intracranial pressure. It can also serve as a route for administering medications directly into the ventricles if necessary.
It is important to note that the EVD is a temporary measure and is usually removed once the underlying condition is resolved or stabilised.
How an external ventricular drain works:
- Placement: A neurosurgeon or a trained healthcare professional inserts a small, flexible catheter into one of the lateral ventricles of the brain. This is usually done through a small hole drilled in the skull called a burr hole. The catheter is then advanced into the ventricular system of the brain.
- Drainage: The external end of the catheter is connected to a drainage system, which consists of a collection bag and a pressure monitoring device. The collection bag collects the drained CSF, and the pressure monitoring device allows healthcare providers to monitor intracranial pressure. By draining the excess CSF, the EVD helps to reduce intracranial pressure and prevent potential damage to the brain.
- Regulation: By opening or closing a stopcock on the drainage system, it is possible to change the rate of CSF drainage. This allows for controlled drainage and the ability to maintain optimal intracranial pressure.
- Monitoring: Once the external ventricular drain is in place, healthcare providers closely monitor the patient’s intracranial pressure and adjust the drainage as needed. They also monitor the volume and characteristics of the drained CSF to assess the patient’s condition.
- Removal: When the excess CSF has been drained and the intracranial pressure is stable, the external ventricular drain can be removed. This is typically done in a controlled manner to prevent complications, and the hole in the skull is often closed with sutures or other appropriate techniques.