What it is
Decompressive hemicraniectomy removes a large section of the skull — typically over one hemisphere — to allow the brain to swell outward rather than compress downward through the skull base, where the brainstem sits. When the brain herniates downward, it compresses the structures that control consciousness, breathing, and basic autonomic function. Creating space prevents this.
The bone flap is stored (in a sterile facility or under the patient's abdominal skin) and replaced in a separate surgery — cranioplasty — once the brain swelling has resolved, typically weeks to months later.
When it is used
Decompressive hemicraniectomy is a last-resort intervention for malignant cerebral edema that has not responded to maximal medical management. The clearest evidence supports its use in:
- Malignant MCA infarction — a massive ischemic stroke involving the entire middle cerebral artery territory, where cerebral edema peaks at 48–72 hours and carries a very high mortality without decompression. Landmark trials show it substantially reduces mortality and, particularly in younger patients, improves functional outcomes.
- Severe TBI — when ICP monitoring shows refractory intracranial hypertension despite all medical measures.
- Large hemorrhagic stroke — selected cases with mass effect and clinical deterioration.
Honest discussion of outcomes
Decompressive hemicraniectomy saves lives. It does not restore the brain damage that preceded the surgery. The conversation with families centers on what quality of life looks like after survival — a deeply individual question that depends on the patient's values, age, baseline function, and degree of neurological injury. This is one of the most significant conversations in neurosurgery, and it should not be rushed.