A craniectomy is a neurosurgical procedure involving the temporary removal of a section of the skull bone. This surgery is performed primarily to manage dangerously high pressure within the brain, known as intracranial hypertension. Since the skull is rigid, swelling from traumatic injury, stroke, or hemorrhage has nowhere to expand, which can compress brain tissue and cause severe damage. Temporarily removing a piece of the skull creates space for the swollen brain to expand outward, which is often a life-saving measure.
Understanding the Craniectomy Procedure
Craniectomy is often necessary following sudden, severe medical events that cause rapid brain swelling, such as severe traumatic brain injuries, large ischemic strokes, or extensive intracerebral hemorrhages. These conditions cause the brain to swell against the cranium, leading to a rapid rise in pressure that compromises blood flow and oxygen supply.
This procedure differs from a craniotomy, where a bone flap is removed to access the brain but is immediately re-secured. In a craniectomy, the bone is left out because the brain swelling is too extensive. The removal creates a temporary open space, allowing the swollen tissue to decompress and preventing potentially fatal herniation of the brainstem.
Temporary Storage of the Bone Flap
Once the bone flap is removed, it is carefully preserved for a later reconstruction procedure. There are two primary methods used by hospitals for temporary storage.
Cryopreservation
One common method is cryopreservation, where the bone is thoroughly cleaned, sterilized, and stored in a specialized freezer or tissue bank. This deep-freeze storage helps preserve the bone’s structural integrity and sterility. Sterile conditions minimize the risk of contamination before the bone is eventually reimplanted.
Subcutaneous Implantation
The second method involves subcutaneous implantation, where the bone flap is placed into a surgically created pocket beneath the skin, often in the patient’s abdomen or thigh. This location acts as a natural incubator, as the body’s environment helps maintain the bone’s cellular viability. While this method keeps the bone biologically viable, it carries a small risk of infection or bone resorption, where the body begins to break down the material.
Life Without the Skull Bone
The period following a craniectomy and before skull reconstruction presents unique challenges and safety requirements. The area of missing bone often has a noticeable sunken appearance, commonly referred to as the “sinking skin flap.” The brain beneath this soft spot is left without the natural protection of the skull, making it highly vulnerable to even minor trauma.
Patients must wear a custom-fitted, hard protective helmet whenever they are out of bed to guard against accidental impact. During this time, some patients may experience Syndrome of the Trephined, or Sinking Skin Flap Syndrome. This syndrome involves neurological deterioration, which can manifest as weakness, headache, dizziness, or cognitive decline. This is thought to be caused by changes in cerebrospinal fluid dynamics and atmospheric pressure effects on the unprotected brain. The patient’s brain swelling must fully subside before the final reconstruction can be safely performed.
Reconstructing the Skull
The final step is a procedure called a cranioplasty, which repairs the defect in the skull bone. Surgeons generally wait several weeks to many months after the initial craniectomy to ensure brain swelling has completely resolved and the patient is medically stable. The specific timing is tailored to the individual, but it is typically performed after a waiting period of three to six months.
During the cranioplasty, the surgeon retrieves the patient’s own stored bone flap or uses a synthetic material to close the defect. The autologous bone flap is the preferred option if it is structurally sound and free from infection. If the original bone was damaged, contaminated, or partially resorbed during storage, the defect is instead repaired using modern synthetic materials.
These synthetic options include custom-made titanium mesh, specialized polymers like polyetheretherketone (PEEK), or bone cement compounds. These materials are precisely modeled using pre-operative imaging to ensure a perfect fit, restoring the protective barrier of the skull.