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By Mayo Clinic Staff

Craniotomy and craniectomy are surgical procedures. They involve removing part of the skull to treat conditions that affect the brain. The main difference between the two surgeries is what happens to the piece of bone that is removed.

A craniotomy is a surgical procedure that temporarily removes a section of skull to reach the brain. After the treatment to the brain, the skull bone flap is replaced and secured with tiny plates and screws during the same surgery. Rarely, larger pieces of metal or plastic also are used.

Craniotomy is used to:

• Remove brain tumors.
• Repair bulging blood vessels called aneurysms or treat bleeding in the brain.
• Remove blood clots.
• Treat seizures.
• Treat blood vessels that did not form properly, called vascular malformations.
• Relieve pressure from brain swelling due to injury or stroke.

A craniectomy is similar to a craniotomy but with one key difference. The piece of skull bone that is removed is not replaced right away. The skull is left open, often to allow the brain room to swell without being squeezed. This sometimes is called a decompressive craniectomy.

Craniectomy usually is done in emergencies when brain swelling is severe. This may include:

• Traumatic brain injury.
• A major stroke affecting the middle cerebral artery, one of the brain's major blood vessels.
• High pressure inside the skull that doesn't get better with medicine or with a ventilator to help the person breathe.

A craniectomy also may be used in some planned brain surgeries. It's done when leaving the bone off or replacing it with other tissue can help protect the brain during recovery.