In urgent situations, or while a longer-term plan is being made, doctors may place a temporary device called an external ventricular drain (EVD) to relieve pressure and drain CSF. If you or a loved one has an EVD — often in an intensive care setting — understanding it can make a frightening situation a little clearer.
What an EVD is An EVD is a temporary catheter placed into a ventricle of the brain that drains CSF out of the body into a collection system at the bedside. Unlike a shunt (which is fully internal and permanent), an EVD is external and temporary — part of it exits through the skin and connects to tubing and a drainage bag, usually mounted on a pole and carefully positioned to control drainage.
Why it's used An EVD serves several important purposes:
- Relieving dangerous pressure quickly — for example, after a serious bleed (such as a hemorrhage) or an acute blockage, when CSF pressure is rising and needs urgent relief.
- Buying time — providing temporary drainage while the underlying situation is treated or stabilized, or while a decision about definitive treatment (shunt or ETV) is made.
- Monitoring pressure — an EVD can also measure the pressure inside the skull, giving the team valuable information.
- Draining infected or bloody CSF — in some infections or hemorrhages, draining the fluid is therapeutic, and the EVD can sometimes be used to deliver medication or clear debris.
Where and how it's managed An EVD is typically managed in an intensive care unit (ICU) or similar monitored setting, because it requires careful, continuous management:
- The drainage system must be kept at a precise height relative to the head to control how much CSF drains — too low drains too much, too high drains too little.
- The team monitors drainage amount, CSF appearance, and pressure, adjusting as needed.
- Strict sterile technique is essential to reduce infection risk.
Because of these demands, patients with an EVD are watched closely by specialized staff.
How long it stays An EVD is temporary — it stays in place for as long as needed to manage the acute situation, often days. As the situation resolves, the team assesses whether CSF drainage is still needed:
- If the hydrocephalus resolves, the EVD can be removed.
- If ongoing drainage is needed, the patient may transition to a permanent solution — a shunt or, in suitable cases, an ETV.
The EVD essentially acts as a bridge — controlling the situation while the path forward becomes clear.
Risks The main risks of an EVD include infection (a key reason for sterile management and limited duration) and, less commonly, bleeding or drainage-related problems. The team balances these risks against the urgent need for drainage and monitoring.
What families should understand Seeing a loved one with an EVD — in an ICU, with tubing and monitors — can be alarming. It helps to know that the EVD is a protective, temporary measure doing crucial work: relieving dangerous pressure and giving the team control and information during a critical period. The care team will explain the plan, including whether a permanent treatment is likely to be needed once the acute situation stabilizes.
The takeaway An external ventricular drain is a temporary, external way to drain CSF and relieve pressure in urgent situations, while also allowing pressure monitoring. It's a vital bridge — stabilizing things and buying time until the hydrocephalus either resolves or a permanent treatment (shunt or ETV) is put in place.