A craniectomy is a neurosurgical procedure performed to relieve severe pressure inside the skull, known as intracranial hypertension. This technique involves removing a section of the skull bone to create space, allowing swollen brain tissue to expand outward safely. It is typically an urgent, life-saving intervention when other medical treatments fail to control dangerous pressure levels within the skull. By temporarily opening this bony compartment, the procedure prevents pressure from compressing the brainstem, mitigating the risk of permanent brain injury or death.
The Key Distinction from Craniotomy
The fundamental difference between a craniectomy and a craniotomy lies in the fate of the bone flap removed during the initial surgery. In a craniotomy, often performed for tumors or aneurysms, the bone flap is immediately replaced and secured to the skull using small plates and screws. The goal of a craniotomy is primarily to gain access to the brain, with the skull defect closed right away.
A craniectomy, however, is a decompressive procedure where the bone flap is intentionally not replaced. This allows the underlying brain to swell without restriction, lowering the dangerous internal pressure.
The surgeon keeps the resulting opening, or cranial defect, exposed beneath the scalp for an extended period, typically weeks to months. This delayed closure is the defining characteristic of a craniectomy, transforming it into a sustained pressure-relief measure. The temporary absence of bone provides a necessary outlet for the brain to expand during the severe phase of swelling following an injury.
Medical Conditions Requiring Craniectomy
The need for a craniectomy arises when medical management cannot stabilize dangerously elevated intracranial pressure (ICP). The skull is a fixed volume, and any swelling or bleeding within it causes pressure to rise quickly, risking brain herniation, where tissue is squeezed across structures within the brain. This surgery is a measure of last resort to prevent this catastrophic outcome.
A primary indication is severe Traumatic Brain Injury (TBI), such as from a major car accident or fall, where the brain tissue swells rapidly in response to the initial trauma. The procedure is performed when this swelling threatens to cause irreversible damage or death. Another common scenario is a Malignant Cerebral Infarction, which is a large ischemic stroke that causes massive brain edema.
In stroke cases, the lack of blood flow leads to tissue death and subsequent swelling. Intracerebral Hemorrhage, or bleeding within the brain, can also necessitate a craniectomy if the pooling blood increases pressure too quickly. The procedure relieves compression caused by both the blood clot and the surrounding tissue swelling.
Steps of the Surgical Procedure
A craniectomy is performed under general anesthesia, beginning with a curvilinear incision of the scalp over the area of the brain that is experiencing the most swelling. The surgeon carefully peels back the skin and muscle layers to expose the underlying skull bone. The process of removing the bone then begins by drilling several small holes, known as burr holes, into the skull along the planned outline of the bone flap.
A specialized surgical saw, called a craniotome, is then inserted into the burr holes to connect them, carefully cutting out a large piece of the skull bone. Once this bone flap is removed, the protective membrane covering the brain, called the dura mater, is exposed. The neurosurgeon then opens the dura mater, often in a star-like pattern, to allow the swollen brain to bulge outward.
The dura is typically left open or loosely closed with a synthetic patch to ensure maximum decompression. This deliberate opening allows the brain to move into the space previously occupied by the bone, effectively reducing the ICP. The removed bone flap must be preserved in a sterile manner for the subsequent procedure, usually involving storage in a deep freezer at a bone bank.
Recovery and Subsequent Cranioplasty
Following the craniectomy, the patient is monitored intensively as the brain swelling subsides over time. Because a portion of the skull is missing, the brain is left vulnerable to external injury, a state known as having a cranial defect. During the recovery period, patients must wear specialized protective headgear, similar to a helmet, whenever they are out of bed to prevent accidental trauma to the exposed brain tissue.
The defect also requires careful positioning while resting to prevent pressure on the underlying brain. Once the acute swelling has resolved and the patient’s condition has stabilized, which can take several weeks to many months, a second procedure becomes necessary. This follow-up surgery is called a cranioplasty, and its purpose is to repair the skull defect.
During the cranioplasty, the original preserved bone flap is retrieved and secured back into place, or a custom-made synthetic implant is used if the original bone is unsuitable. This second surgery restores the physical protection of the skull and corrects the cosmetic defect. Repairing the skull is a necessary step for long-term recovery and neurological function.