Craniotomy Procedure

By Marian C. O'Brien, RN, MPH

Procedure Overview

What is a craniotomy?

A craniotomy is the surgical removal of part of the bone from the skull to expose the brain. Specialized tools are used to remove the section of bone called the bone flap. The bone flap is temporarily removed, then replaced after the brain surgery has been performed.

Some craniotomy procedures may utilize the guidance of computers and imaging (magnetic resonance imaging [MRI] or computerized tomography [CT] scans) to reach the precise location within the brain that is to be treated. This technique requires the use of a frame placed onto the skull or a frameless system using superficially placed markers on the scalp. When either of these imaging procedures is used along with the craniotomy procedure, it is called stereotactic craniotomy.

Scans made of the brain, in conjunction with these computers and localizing frames, provide a three-dimensional image, for example, of a tumor within the brain. It is useful in making the distinction between tumor tissue and healthy tissue and reaching the precise location of the abnormal tissue.

Other uses include stereotactic biopsy of the brain (a needle is guided into an abnormal area so that a piece of tissue may be removed for examination under a microscope), stereotactic aspiration (removal of fluid from abscesses, hematomas, or cysts), and stereotactic radiosurgery (such as gamma knife radiosurgery).

An endoscopic craniotomy is another type of craniotomy that involves the insertion of a lighted scope with a camera into the brain through a small incision in the skull.

Aneurysm clipping is another surgical procedure which may require a craniotomy. A cerebral aneurysm (also called an intracranial aneurysm or brain aneurysm) is a bulging weakened area in the wall of an artery in the brain, resulting in an abnormal widening or ballooning. Because of the weakened area in the artery wall, there is a risk for rupture (bursting) of the aneurysm. Placement of a metal clip across the "neck" of the aneurysm isolates the aneurysm from the rest of the circulatory system by blocking blood flow, thereby preventing rupture.

Craniectomy is a similar procedure that involves the permanent removal of a portion of the skull. This is done if swelling is likely after brain surgery or if the skull bone flap cannot be replaced for other reasons.

Other related procedures that may be used to diagnose brain disorders include cerebral arteriogram, computed tomography (CT) scan of the brain, electroencephalogram (EEG), magnetic resonance imaging (MRI) of the brain, positron emission tomography (PET) scan, and x-rays of the skull. Please see these procedures for additional information.

Anatomy of the brain

The brain and spinal cord make up the central nervous system (CNS). The CNS controls all the functions of the body such as vision, taste, touch, muscle movement, breathing, thought, behavior, memory, and emotion. Every process in the body is affected by the brain.

What are the different sections of the brain?

The brain has three main sections, the cerebrum, brainstem, and cerebellum. Each section has unique functions:

  • cerebrum
    The cerebrum (forebrain or front brain) is the largest section of the brain. It is composed of right and left hemispheres, which control the opposite sides of the body. For example, the left side of the brain controls the right side of the body, along with speech. Functions of the cerebrum include initiation and coordination of movement, sensation, touch, vision, hearing, judgment, reasoning, problem solving, emotions, learning, and control of body temperature.

  • brainstem
    The brainstem (mid brain) includes three divisions: midbrain, pons, and medulla. Here information is relayed between the peripheral nerves and spinal cord to the upper parts of the brain

    Some specific functions of the brainstem include:

    • control of vital signs, such as breathing, heart rate, and blood pressure

    • alertness

    • sleepiness

    • eye movement

    • involuntary muscle movements such as sneezing, coughing, vomiting, yawning, and swallowing

  • cerebellum
    The cerebellum (back brain) is located in the back of the skull. Its function is to coordinate voluntary muscle movements and to maintain posture and balance.