External ventricular drain

An external ventricular drain (EVD) is a small, temporary tube placed in the brain to drain extra fluid. It’s typically used when sudden bleeding, infection or injury blocks the regular flow of fluid through the brain.

The EVD helps relieve pressure in your head and keeps your brain safe. It’s a temporary solution until your body can manage the fluid on its own or another treatment is done.

The procedure to place an EVD is done in a hospital, typically by a neurosurgeon. This may happen in the operating room, emergency room or intensive care unit.

Parts of an EVD system

The EVD system consists of several key parts. These parts work together to drain the fluid, called cerebrospinal fluid (CSF), and monitor and manage the pressure inside your head, called intracranial pressure (ICP).

• Catheter. The catheter is a thin, flexible tube inserted into spaces inside the brain called ventricles, where CSF is made and collects. The catheter is the main part of the drainage system. It leads from the ventricles to the collection system next to your hospital bed. Some catheters are coated with antibiotics or silver to reduce the risk of infection.
• Collection system. The collection system includes a drainage bag and tubing connected to the catheter. This system collects the CSF that is drained from the brain. It can be adjusted to control how much fluid is drained. This is critical to maintaining a safe intracranial pressure. Problems can occur if pressure is too high, resulting in underdrainage, or too low, resulting in overdrainage.
• Pressure monitoring system. The EVD system is equipped with a device called a transducer that measures your intracranial pressure. This helps your healthcare team monitor your intracranial pressure and know when to adjust the drainage system to keep a consistent pressure level.

An external ventricular drain is typically part of emergency care when your healthcare team suspects a buildup of cerebrospinal fluid in the brain, called hydrocephalus.

An EVD also may be used before, during or after surgery for a brain tumor.

Emergency care

Sudden hydrocephalus can develop for many reasons:

• Bleeding and fluid accumulation caused by bleeding in the space between the brain and the tissues that cover the brain. This is called a subarachnoid hemorrhage. It can happen after an aneurysm bursts.
• Swelling or bleeding in the brain caused by traumatic brain injury.
• Swelling in the brain caused by infections such as meningitis or encephalitis.
• Obstructed fluid drainage caused by a brain tumor.
• Swelling and fluid in the brain during or after brain surgery.
• Infection of an existing brain shunt.

The fluid buildup can increase pressure in the skull, leading to symptoms such as headache, confusion, nausea and drowsiness. If pressure builds to a point where you’re losing consciousness and brain functions are impaired, an external ventricular drain can be lifesaving. The EVD can quickly relieve the pressure, protect brain tissue from damage and improve symptoms.

Care for brain tumors

Sometimes, an EVD is placed in connection with brain tumor surgery to treat or prevent hydrocephalus. For example, medulloblastomas, brain tumors that grow in the lower back part of the brain, often cause hydrocephalus, especially in children. An EVD may be placed to relieve pressure on the brain before surgical removal of the tumor. It also may be in place during surgery to help surgeons clearly see the area they’re operating on and to help promote healing after surgery.

Hydrocephalus is a common complication after brain tumor surgery. An EVD may be used to treat this. Sometimes an EVD is placed as a preventive measure before surgery if your surgeon suspects a high chance of hydrocephalus developing after surgery.

Intracranial pressure monitoring

An EVD may be used to monitor your intracranial pressure. When intracranial pressure gets too high or too low, it can cause damage to the brain. Draining fluid as needed using the EVD can help keep the pressure in a safe range.

An external ventricular drain is often a lifesaving procedure. It does have risks, however. Risks may include:

• Infection of the EVD system. Infection can happen if bacteria enter the brain through the EVD. Healthcare professionals use sterile techniques and antibiotics to prevent this. Also, there are special EVD catheters coated with antibiotics to help prevent infections.
• Bleeding along the EVD path. During EVD placement, there’s a small risk of bleeding in the brain along the path of the catheter.
• EVD blockage. Blood clots or tissue may clog the drain tube. If this happens, the EVD may need to be adjusted or replaced.
• Misplacement of the EVD catheter. Sometimes, the EVD may not be positioned correctly in the brain, requiring the EVD to be adjusted or replaced.
• Overdrainage of fluid from the brain. In some cases, the EVD may drain too much fluid from the brain. This can cause blood vessels to tear and cause blood to collect on the surface of the brain. This is known as a subdural hematoma.

An external ventricular drain procedure is typically an emergency procedure. Most of the preparation is done by your healthcare team in the operating room, emergency room or intensive care unit.

You or the person you’re with may feel overwhelmed by all the activities around you. There is a lot going on. But EVD placement is a common procedure and many hospitals have experience with it.

Before the procedure

• Imaging tests. Before the EVD is placed, your healthcare team does a CT or MRI scan of your head to plan the catheter’s placement.
• Medicines. If you’re taking any blood thinners, these are stopped. You may receive medicine to reverse the action of blood thinners you’ve taken. You’ll receive antibiotics to prevent infection, which is a frequent complication of EVD placement if preventive steps aren’t followed.
• Anesthesia. If you’re awake during the procedure, you’ll get local anesthesia to numb the area. In emergencies, sedation may be necessary. Sedation is a form of anesthesia that allows you to relax and be comfortable during a procedure.
• Positioning and skin prep. During the procedure, you lie on your back with your head slightly elevated. Your scalp is cleaned and shaved where the EVD will be inserted. Your surgeon marks the entry point for the EVD, usually on the right side of your forehead, above your temple.

During the procedure

To place an EVD:

• A small opening in the scalp is created.
• A small hole is drilled through the skull bone.
• A thin tube called a catheter is passed through the brain tissue and into a ventricle to drain fluid.
• The catheter is secured to the scalp with stitches and connected to a drainage system.

After the procedure

After the procedure, your healthcare team closely monitors your heart rate, breathing and blood pressure. You may feel tired or a bit confused. You may experience a mild headache, nausea or swelling around the incision site.

Next steps include:

• Additional imaging test. Another CT scan is done to make sure the catheter is in the right place.
• Monitoring. Your healthcare team monitors you closely to make sure the EVD is working properly. The team checks for signs of infection or bleeding, asks you questions, and does tests to check your brain function.
• Pressure management. The EVD may be used to monitor your intracranial pressure. It also can be used to drain excess fluid when necessary to maintain pressure at a consistent level.

As your condition improves, so does the flow of cerebrospinal fluid. Your healthcare team typically runs a trial period where the EVD stays in place but is not actively draining. If your intracranial pressure stays at a safe level, the EVD can be removed and the skin incision closed with stitches. If symptoms continue and ongoing fluid drainage is necessary, your healthcare team may recommend a permanent solution, such as a brain shunt.

Generally, healthcare professionals try to remove the EVD as soon as possible to minimize the risk of the drain getting infected.

When intracranial pressure is high for too long, it can be fatal. An EVD is often a life-saving procedure. The benefits usually outweigh the risks.

How long you stay in the hospital after EVD removal depends on your overall condition. An EVD placement itself is generally low risk. But conditions such as stroke and bleeding in the brain, traumatic brain injury and brain tumor typically require additional treatments.