craniotomy

(krā'nē-ŏt'ə-mē)
n., pl., -mies.

1. Surgical incision into the skull.
2. The cutting or breaking of the fetal skull to reduce its size for removal when normal delivery is not possible.

View more Health videos

Key Terms: Craniotome, Computed tomography (CT or CAT) scan.

Definition

A craniotomy is the surgical removal of part of the skull to expose the brain.

Purpose

A craniotomy is the most commonly performed surgery to remove a brain tumor. It may also be done to remove a blood clot and control hemorrhage, to inspect the brain, to perform a biopsy, or to relieve pressure inside the skull.

Precautions

The outcome of surgery will depend on the type and location of the tumor. Radiation therapy or chemotherapy are sometimes given before surgery to shrink the tumor.

Description

There are two basic ways to open the skull. A curving incision may be made from behind the hairline, in front of the ear, to arch above the eye, or at the nape of the neck around the occipital lobe. The surgeon marks with a felt tip pen a large square flap on the scalp that covers the surgical area. Following this mark, the surgeon makes an incision into the skin as far as the thin membrane covering the skull bone. Because the scalp is well supplied with blood, the surgeon will have to seal many small arteries. The surgeon then folds back a skin flap to expose the bone.

Using a high speed hand drill or an automatic craniotome, the surgeon makes a circle of holes in the skull and pushes a soft metal guide under the bone from one hole to the next. A fine wire saw is then moved along the guide channel under the bone between adjacent holes. The surgeon saws through the bone until the bone flap can be removed to expose the brain.

After the surgery for the underlying cause is completed, the piece of skull is replaced and secured with pieces of fine, soft wire. Finally, the surgeon sutures the membrane, muscle, and skin of the scalp.

Recent advances in computer-assisted technology have enhanced this operation. Image-guided craniotomy uses information from magnetic resonance imagining scans (MRIs) or computed tomography (CT) scans to produce three-dimensional images of the brain for the surgeon before the operation is begun. This makes it possible for the surgeon to remove less skin and bone, to tell exactly where the tumor stops and the healthy brain begins, and to remove tumors that were previously too deep for surgery.

Preparation

Before the operation, the patient undergoes diagnostic procedures such as CT and MRI scans to determine the underlying problem that requires the craniotomy and to get a better look at the brain's structure. Cerebral angiography is a diagnostic procedure that may be used to study the blood supply to the tumor, aneurysm, or other brain lesion.

Before the surgery, patients are given drugs to ease anxiety, and other medications to reduce the risk of swelling, seizures, and infection after the operation. Fluids may be restricted, and a diuretic (water pill) may be given before and during surgery if the patient has a tendency to retain water. A urinary catheter is inserted before the patient goes to the operating room. The scalp is shaved in the operating room immediately before surgery; this is done so that any small nicks in the skin won't have a chance to become infected before the operation.

Aftercare

Oxygen, painkillers, and drugs to control swelling and seizures are given after the operation. Codeine may be given to relieve potential headaches caused by the stretching or irritation of the nerves of the scalp. Some type of drainage from the head may be in place, depending on the reason for the surgery.

Patients are usually out of bed within a day and out of the hospital within a week. Headache and pain from the scalp wound can be controlled with medications. Some patients will receive radiation therapy or chemotherapy after surgery.

The bandage on the skull should be changed regularly. Sutures closing the scalp will be removed, but soft wires used to reattach the skull are permanent and require no further attention. The patient should avoid getting the scalp wet until all the sutures have been removed. A clean cap or scarf can be worn until the hair grows back.

Risks

Accessing the area of the brain that needs repair may damage other brain tissue. Therefore, the procedure carries with it risk of brain damage that could leave the patient with some loss of brain function. The surgeon performing the operation can give the patient an assessment of the risk of his or her particular procedure based on the location of the tumor.

Normal Results

While every patient's experience is different depending on the reason for the surgery, age, and overall health, recovery from a successful surgery is usually rapid because of the good supply of blood to the area.

Abnormal Results

Possible complications after craniotomy include:

• swelling of the brain
• excessive intracranial pressure
• infection
• seizures

Resources

Organizations

American Cancer Society. 1599 Clifton Road NE, Atlanta, GA 30329. 800 (ACS)-2345). .

Cancer Information Service, National Cancer Institute. Building 31, Room 10A19, 9000 Rockville Pike, Bethesda, MD 20892. (800) 4-CANCER. .

—Carol A. Turkington

By derivation, this word covers any surgical opening into the skull, but it is now usually used only to describe the fashioning of a hinged flap of bone which allows the intracranial cavity to be reached. Opening the skull (trepanning) in the belief that this would let out evil spirits is one of the oldest operations in the history of surgery, as evidenced by the finding of man-made holes in skulls from very early periods. In these cases, pointed flints were probably used to bore out the hole, and some skulls show evidence of subsequent healing with new bone formation — indicating that people survived such procedures. Until the middle of the twentieth century, skull openings were still being made by some tribes in Kenya. Indications probably included mental illness, epilepsy, and perhaps severe, recurrent headache such as migraine. Recently an eccentric small group have advocated do-it-yourself drilling of the skull, supposedly to restore the alleged benefit of allowing a pressure outlet similar to that in infancy before the fontanelle closes. Technical instructions for this bizarre procedures have even appeared on the Internet.

Diagram of frontal craniotomy: (a) burrholes; (b) the hinged flap


By the seventeenth century the ‘trephine’ was an instrument in the surgical armamentarium for opening the skull. This was a circular crown saw with a central pin, which would cut out a disc or button of bone. It could vary in diameter from 1 cm or so up to 8 cm; sometimes more than one disc was cut to give adequate access. The larger discs would be put back in place, but smaller holes were left as permanent defects. A further development was to use a brace and bit to ream out (as bone dust) burr holes about 1 cm in diameter. Through trephine or burr holes, blood clots that were threatening life by compression of the brain could be let out, and lives were saved. Burr holes are still used today for releasing surface clots and also to allow probes to be passed into deeper parts of the brain. These may be for measuring the pressure in, or draining fluid from, the cerebral ventricles; for obtaining biopsy specimens of brain for microscopic examination; to record electrically from the deeper parts of the brain; or to produce controlled damage in parts of the brain for the correction of abnormal functioning (e.g. epilepsy or tremor). The limited access provided by a burr hole may be increased by nibbling away more bone with forceps, the resulting procedure being termed craniectomy. This leaves a permanent defect in the skull, with the brain covered only by the skin and other soft tissues.

The Gigli saw, invented by this Florentine obstetrician in 1894 to enlarge the pelvic outlet in obstructed labour, made the craniotomy flap possible. This saw is a serrated wire that can be passed under the bone from one burr hole to the next one and used to saw the bone in between. This is done along the lines joining each pair of burr holes, except the line which underlies the fold of skin and other tissues that has been turned back. This base section of unsawn bone is then cracked as the bone flap is raised. The bone flap remains hinged on the soft tissues attached to it, preserving its blood supply (see figure). This allows major intracranial surgery to be performed, such as the removal of a tumour, and when this has been completed the bone flap can be turned back into place and the soft tissues and skin also replaced. The use of a brace and bit and Gigli saw has recently been replaced by power driven drills and saws.

An unusual use of the term ‘craniotomy’ is in obstetrics. This is when a dead baby with an abnormally large head has caused obstructed labour, and the obstetrician has to reduce the size of the head by perforating it in order to allow delivery.

— Bryan Jennett

1. any operation on the cranium.
2. puncture of the skull and removal of its contents to decrease the size of the head of a dead fetus and facilitate delivery.

n

Any surgical opening into the skull, performed to relieve intracranial pressure, to control bleeding, or to remove a tumor.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)