Definition and Overview

A craniotomy is a surgical procedure that involves a portion of the skull called the cranium, which protects the brain.

The skull is composed of more than 20 different bones; eight of them make up the cranial skull. In early childhood, these bones are separate giving the brain room to grow and develop. During adulthood, they fused together leaving very small gaps for the nerves and blood vessels.

In a craniotomy, a portion of the skull known as the bone flap is opened or removed to access the brain, to perform a biopsy, or reduce intracranial pressure. If the bone is returned to its original position, screws and metal plates are used to secure it. The procedure is referred to as craniotomy if the bone flap is removed permanently.

There are different types of craniotomies that are grouped according to the affected section of the brain and technique used. Under location, the procedures are named based on the part of the brain that is being accessed. These include parietal, suboccipital, frontotemporal, and temporal. However, there are cases wherein the procedure is performed in more than one region of the brain.

When it comes to technique, a craniotomy may be keyhole or burr (involves drilling the skull to create a hole) or skull base surgery if it is considered complex or sensitive.

Brain surgeries are performed by neurosurgeons, doctors who have completed at least one year of neurology residency and around six years of fellowship in surgery. Neurosurgeons can work with other types of surgeons like those who specialize in plastic surgery or head and neck, particularly during skull base surgery.

Who should undergo and expected results

Craniotomy may be performed to:

  • Remove or treat brain-related conditions – These can include brain tumors (both benign and malignant), aneurysm, or traumatic injury. These problems can lead to intracranial pressure or the buildup of cerebrospinal fluid pressure. As a life-threatening condition, it can lead to permanent neurological damage or even death when not treated promptly.
  • Relieve intracranial bleeding – Intracranial bleeding means there's an accumulation of blood in the brain due to a bursting of an artery, which is often due to preexisting conditions like the buildup of pressure inside the wall or a traumatic brain injury. This can lead to intracranial bleeding and the death of the brain cells.
  • Perform a biopsy – This involves obtaining a sample tissue from the brain for microscopic analysis. This is a common procedure to determine malignancy in tumors.
  • Perform an aspiration – Slightly similar to a biopsy, an aspiration is the collection of a fluid sample for further analysis.
  • Treat a blood clot – Blood clots form when there's an injury causing the platelets to group together. This can block the arteries and increase the pressure inside the brain.
  • Treat fractures to the skull – The skull is one of the strongest bones in the body as it protects the brain, which is very soft. However, it can be fractured due to strong traumatic impact.
  • Implant a device – Neural implants are commonly used to bypass areas of the brain that may no longer be working due to a condition like stroke or an injury.

How the procedure works

Prior to the brain surgery, the neurosurgeon and the patient sit down for extensive consultation and planning. At this stage, the neurosurgeon covers:

  • Reasons for craniotomy
  • The actual technique to be used
  • Step-by-step procedure
  • Recovery and follow-up care
  • Risks and complications
  • Pre-surgery care and exam
  • Costs
  • Prognosis

Under the pre-surgery care, the patient is expected to:

  • Discuss medical history including medications being taken, preexisting conditions, habits like smoking, and other factors that can affect the surgery and its outcome
  • Undergo several physical and neurological tests to ensure that the patient is physically and mentally fit to undergo the procedure
  • Prepare for the procedure by quitting smoking, taking certain medications like steroids to regulate swelling, shampooing with an antiseptic, and staying in the hospital for a couple of days, among others
  • Coordinate with the rest of the surgical team including the anesthesiologist

During the actual procedure:

  • The patient is wheeled into the operating room wearing a lab or surgical gown. He is then assisted to lie on the operating table.
  • The anesthesia is then administered usually through an IV line to keep the patient comfortable. In an awake brain surgery, the patient stays awake after the skull is opened.
  • The patient is then connected to a machine that monitors vital readings like blood pressure and heart rate. A catheter is also inserted into the bladder to drain urine.
  • Hair in the surgical site is shaved and antiseptic is applied.
  • The surgeon then accesses the skull by using a drill.
  • To remove the bone flap, a special saw is used.
  • The first thing the surgeon sees is the dura mater or the outer layer of the brain's meninges. The dura mater is slowly open until the brain is exposed.
  • The surgeon then begins the brain treatment using small surgical instruments. In some cases, an endoscope or an MRI is used to guide the surgeon. If there's a fluid overflow, which is normal in the event of intracranial pressure or bleeding, it is drained first before the surgeon begins to operate.
  • After the procedure, the opened tissues are sutured. The bone flap is then returned and secured with wires, screws, and metal plates.
  • The skin incision is also sutured, and the head is properly bandaged.

Possible risks and complications

Brain surgery is an extremely delicate procedure and comes with very serious risks and complications. During the surgery, intracranial pressure may suddenly increase, threatening the brain tissue. Infection can also develop, including in the bone flap, which means it cannot be returned. There may also be swelling and bleeding in the surgical site.

Other possible complications include muscle or limb weakness, disorientation, behavior change, seizure, pain, vision changes, blood clot formation, and brain inflammation.


  • Gasco J, Mohanty A, Hanbali F, Patterson JT. Neurosurgery. 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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