Craniectomy after Head Trauma

A Craniectomy Reduces Pressure on the Brain

A serious complication after severe head trauma is swelling and bleeding of the brain. In order to prevent further brain damage from high pressures inside the skull it may be necessary to perform a surgery called a craniectomy.

Why the Brain Swells

When the head receives a powerful blow, the brain slams into the front, back and sides of the bony skull. The brain is bathed in cerebrospinal fluid and also filled with blood.

This means the blow causes a ripple effect throughout the brain. As the brain is shaken, twisted and rocked, cerebral tissues and nerve cells may tear. Blood vessels may rupture and bleed. Bleeding can also occur throughout the tissue layers that cover the outside surface of the brain.

The skull surrounds the entire brain, so when blood and swelling begin to fill up the space inside the skull, it squeezes the brain.

Consider a serious knee injury. After the knee is injured, fluid collects between the bones and ligaments of the knee and causes swelling of the knee. This is clearly visible, and sometimes the fluid around the knee can even been physically manipulated.

While this is a clear problem, the knee is able to accommodate all of that swelling by expanding outward. However, the brain can’t swell beyond the skull. It has nowhere to go.

Intracranial Pressure

This causes an immediate rise in brain pressure, which is called intracranial pressure, or ICP by medical professionals.

The heart continues to push blood into the brain, but broken blood vessels cause this blood to leak into and around the brain. Ruptured nerve cells also release chemicals and fluids.

As blood, fluid and swelling increase, the ICP also increases. This high intracranial pressure makes it difficult for blood and oxygen to reach vital areas of the brain that are required for staying alive.

The brain controls processes such as blood pressure, heart rate and breathing. Pressure on any of these areas of the brain is a medical emergency. This is why doctors have to perform surgery to relieve some of the pressure.

Craniectomy for Brain Injury

Expert surgeons trained in managing head trauma can help in these situations. They often choose a procedure called a craniectomy. A craniectomy is a relatively straightforward surgery in which a portion of the skull is removed so the brain has room to swell. The brain will actually swell beyond the skull after a craniectomy, so the surgeon places protective covering over the surface of the exposed brain.

The removed bone is often placed under the skin elsewhere in the body, for example under the tissues of the abdomen. This preserves the bone and also helps reduce the risk of infection later, when brain swelling has gone down far enough to put the bone back in the skull.

Monitoring Brain Swelling

During the craniectomy the neurosurgeon may also insert a couple of devices, if they are not already in place.

One is a simple probe that measures the ICP inside the brain. In the intensive care unit, this probe is hooked up to a monitor that continuously records brain pressure. Normal ICP runs between 5 -15 mm/hg, and interventions to bring down ICP usually begin when the ICP hits 20 mm/hg.

Parameters are set and an alarm will sound if the brain pressure gets dangerously high. The ICP monitor is used to guide additional treatments, and assess how well the patient tolerates activities such as turning, or other procedures.

A shunt that drains fluid from deeper inside the brain may also be placed. The nature of the injury, associated swelling and other factors help the surgeon decide if a shunt is needed. When pressure in the brain goes up, ICU nurses have the ability to drain fluid from the brain in order to help bring that pressure down.

Once the swelling has subsided, and pressures are within a safe range, another surgery replaces the skull bone and closes the skull.


Baldo S, Tacconi L. (2010) Effectiveness and safety of subcutaneous abdominal preservation of autologous bone flap after decompressive craniectomy: a prospective pilot study. World Neurosurg. 2010 May;73(5):552-6.

Deok-ryeong Kim, M.D., Seung-Ho Yang, M.D., Jae-hoon Sung, M.D., Sang-won Lee, M.D., and Byung-chul Son, M.D., Ph.D (2014) Significance of Intracranial Pressure Monitoring after Early Decompressive Craniectomy in Patients with Severe Traumatic Brain Injury J Korean Neurosurg Soc. 2014 Jan; 55(1): 26–31.

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