Definition and Overview

A craniectomy, or bone flap removal, is a neurosurgical procedure used to relieve pressure on the brain by removing a portion of the skull. It is often used as a life-saving measure following a traumatic brain injury that leads to excessive swelling of the brain or bleeding around it, placing the patient at risk of brain compression and brain death. It also ensures that the patient retains all basic vital functions while the brain is recovering. The procedure can be reversed by placing the bone back once the swelling in the brain subsides. Although the procedure is quite complex, a craniectomy is made possible by the advances in precision cutting technology and post-operative antibiotic care.

A craniectomy should not be confused with a craniotomy. Although both involve the removal of a flap of bone from the skull, a craniotomy only does so to gain access to the brain for treatment. The flap of bone is then put back and secured with screws at the end of the same procedure, whereas in a craniectomy, it may take several months before the flap is replaced.

Who Should Undergo and Expected Results

Also known as decompressive craniectomy or bone flap removal, this procedure is most commonly performed on patients who suffer from:

  • Stroke
  • Traumatic brain injury
  • Malignant edema
  • Intracranial hypertension
    It is more widely performed on patients who are under 50 years of age, as younger patients are shown to have a better prognosis following the procedure than patients who are aged over 50. The procedure is also sometimes performed on children, with paediatric patients showing a good overall recovery rating and with results proving more advantageous compared to non-surgical treatment methods.

In most cases, however, the procedure is done as a last resort and as a means of saving the patient’s life. A craniectomy can do so in two ways. First, the procedure relieves the pressure caused by intracranial bleeding and swelling. By removing a part of the skull, the brain is given the space to expand. The procedure is also used to treat the source of bleeding and remove any blood clot that may have formed.

Second, a craniectomy prevents brain decompression, a serious condition that causes the brain to swell downwards, compressing the brainstem and, as a result, affecting the patient’s basic vital functions.

How Does the Procedure Work?

During a craniectomy, the patient is administered with general anaesthesia and his vital signs are closely monitored. The neurosurgeon will first make an incision on the scalp taking into consideration where bleeding and swelling are located. The skin and the soft tissues are first moved out of the way to gain access to the skull, which is then drilled at specific spots. The drilled holes are then connected using a saw to make one big hole and detach a piece of the skull. If there is a blood clot, the surgeon will locate and evacuate it. If there is active bleeding, the surgeon will take the necessary steps to control it. Once all these have been done, the surgeon will put the soft tissues back and stitch the scalp closed.

After the procedure, the patient is given a special helmet to protect his head and prevent further injury.

The bone removed during a craniectomy is usually stored in a freezer to preserve it for re-attachment when the swelling of the brain subsides and the patient’s condition stabilises. This process may take as much as several months. The procedure to replace the removed bone and close the opening in the skull is called a cranioplasty. Before the bone can be put back in place, however, it is first tested for bacteria to ensure that it can still be used. If bacterial growth is detected, it will be replaced with a synthetic skull.

There is no standard length of hospital stay required for a patient who undergoes a craniectomy. In most cases, the patient is already in a critical condition that requires extended hospital stay. The patient will, therefore, stay in the hospital until his condition stabilises, a process that can take anywhere between a few months to a couple of years, depending on the extent of the injury to the brain.

Possible Risks and Complications

Although the medical benefits of a bone flap removal are clear, some questions remain as to whether it should be performed or not, leading to some controversy about its use. Some of the questions relate to its complication rate, the justification of its results (i.e. does it leave the patient in a much better position than when it is not performed), and its efficacy in controlling symptoms of brain injury such as brain herniation and brain edema.

As a complex neurosurgical procedure, a craniectomy is associated with a number of major risks, such as:

  • Bleeding
  • Infection, such as brain abscess and meningitis
  • Further brain damage leading to permanent disability
  • Compromised brain function
  • Increased risk of brain injury, mainly due to the compromised strength of the skull. To control this risk, some patients undergo a cranioplasty, in which the opening in the skull is closed using either the original bone flap or a synthetic alternative.
    It is possible for a patient who undergoes a craniectomy to suffer from compromised brain function after the procedure. Thus, rehabilitation is recommended to restore the full function of the brain.

Since patients who require a bone flap removal are often already in a very critical condition, the benefits of the procedure usually outweigh these risks. In most cases, the possible damage of brain compression is worse than the potential damage that can occur when the procedure is performed. Moreover, neurosurgeons take steps to ensure that the risks of the procedure are minimised, such as administering antibiotics before and after the procedure and avoiding unnecessary manipulation of the brain.


  • Gasco J, Mohanty A, Hanbali F, Patterson JT. Neurosurgey. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 19th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 68.
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