Craniotomy is a surgery to cut a bony opening in the skull. A section of the skull, called a bone
flap, is removed to access the brain underneath. A craniotomy may be small or large depending on the problem. It may be performed to treat brain
tumors, hematomas (blood clots), aneurysms or AVMs, skull fractures, foreign
objects (bullets), swelling of the brain, or infection. The bone
flap is usually replaced at the end of the procedure with tiny
plates and screws.
What is a craniotomy?
Craniotomy is any
bony opening that is cut into the skull (cranium) to access the brain underneath. There are many types of craniotomies, which are named according to the area of skull to be removed (Fig. 1). The
bone flap is replaced and secured with plates and screws. If the bone flap is not
replaced, it is called a craniectomy.
Craniotomies are often named for the bone being
removed. Some common craniotomies include frontotemporal,
parietal, temporal, and suboccipital.
Craniotomies vary in
size and complexity. Small dime-sized craniotomies are called burr holes; "keyhole" craniotomies are quarter-sized or larger.
Stereotactic frames, image-guided computer systems, or endoscopes may be used to precisely place instruments through these small holes.
holes and keyholes are used for minimally invasive procedures to:
- insert a shunt into the ventricles to drain
cerebrospinal fluid (hydrocephalus)
- insert a deep brain
- insert an intracranial pressure (ICP) monitor
- remove a small sample of tissue cells
- drain a blood clot (hematoma
- insert an endoscope to remove tumors
Complex skull base craniotomies involve the removal of bone that supports the bottom of the brain where delicate cranial nerves,
arteries, and veins exit the skull. Reconstruction
of the skull base may
require the additional expertise of head-and-neck,
otologic, or plastic surgeons. Surgeons
often use image-guidance systems to plan the access
for difficult-to-reach lesions to:
- remove deep brain tumors or AVMs; clip aneurysms
- remove tumors that invade the bony skull
While most skull openings are made as small as possible, large decompressive craniectomies are made to allow the brain to swell after a head trauma or stroke. The bone flap is frozen and replaced months later after recovery (cranioplasty).
There are many kinds of craniotomies.
Ask your neurosurgeon to describe where
the skin incision will be made and the amount
of bone removal.
Who performs the procedure?
A craniotomy is performed by a neurosurgeon; some have additional training
in skull base surgery. A neurosurgeon may work with a team
of head-and-neck, otologic, oculoplastic and
reconstructive surgeons. Ask your neurosurgeon about
their training, especially if your case is complex.
What happens before surgery?
You will typically undergo tests
(e.g., blood test, electrocardiogram, chest
X-ray) several days before surgery. In the doctors
office you will sign consent forms and complete paperwork to inform the surgeon about your
medical history (i.e., allergies, medicines,
anesthesia reactions, previous surgeries). You
may wish to donate blood several weeks before
surgery. Discontinue all non-steroidal
anti-inflammatory medicines (Naproxin, Advil,
etc.) and blood thinners (coumadin, aspirin,
etc.) 1 week before surgery. Additionally,
stop smoking, chewing tobacco, and drinking
alcohol 1 week before and 2 weeks after surgery
because these activities can cause bleeding problems.
What happens during surgery?
There are 6 main steps during a craniotomy.
Depending on the underlying problem being treated and complexity,
can take 3 to 5 hours or longer.
1: prepare the patient
No food or drink is permitted past midnight the night before surgery. Patients are admitted to the hospital the morning of the craniotomy. With an intravenous (IV) line placed in your arm, general anesthesia is administered while you lie on the operating table. Once asleep, your
head is placed in a 3-pin skull fixation
device, which attaches to the table and holds
your head in position during the procedure (Fig.
2). Insertion of a lumbar drain in your lower
back helps remove cerebrospinal fluid (CSF), thus
allowing the brain to relax during surgery. A brain-relaxing
drug called mannitol may be given.
The patient’s head is placed in a three-pin
Mayfield skull clamp. The clamp attaches to
the operative table and holds the head absolutely
still during delicate brain surgery. The hair is shaved along the skin
Step 2: make a skin incision
After the scalp is prepped with an antiseptic, a skin incision is made, usually behind the hairline.
The surgeon attempts to ensure a good cosmetic result after surgery. Sometimes
a hair sparing technique can be used that requires
shaving only a 1/4-inch wide area along the proposed
incision. Sometimes the entire
incision area may be shaved.
Step 3: perform a craniotomy, open the skull
The skin and muscles are lifted off the bone
and folded back. Next, one or more small burr
holes are made in the skull with a drill. Inserting a special saw through the burr holes, the
surgeon uses this craniotome to cut the outline of a bone flap (Fig.
3). The cut bone flap is lifted and removed
to expose the protective covering of the brain
called the dura. The bone flap is safely stored
until it is replaced at the end of the procedure.
A craniotomy is cut with a special saw called
a craniotome. The bone flap is removed to reveal
the protective covering of the brain called
Step 4: expose the brain
After opening the dura with surgical scissors, the surgeon folds it
back to expose the brain (Fig. 4). Retractors
placed on the brain gently open a corridor
to the area needing repair or removal. Neurosurgeons
use special magnification glasses, called loupes,
or an operating microscope to see the delicate
nerves and vessels.
Figure 4. The dura is opened and folded back to expose the brain.
Step 5: correct the problem
Because the brain is tightly enclosed inside
the bony skull, tissues cannot be easily moved
aside to access and repair problems. Neurosurgeons
use a variety of very small tools and instruments
to work deep inside the brain. These include
long-handled scissors, dissectors and drills,
lasers, ultrasonic aspirators (uses a fine jet
of water to break up tumors and suction up the
pieces), and computer image-guidance systems.
In some cases, evoked potential monitoring is
used to stimulate specific cranial nerves while
the response is monitored in the brain. This
is done to preserve function of the nerve and
make sure it is not further damaged during surgery.
Step 6: close the craniotomy
With the problem removed or repaired, the
retractors holding the brain are removed and
the dura is closed with sutures. The bone flap
is replaced back in its original position and
secured to the skull with titanium plates and
screws (Fig. 5). The plates and screws remain
permanently to support the area; these can sometimes
be felt under your skin. In some cases, a drain
may be placed under the skin for a couple of
days to remove blood or fluid from the surgical
area. The muscles and skin are sutured back
together. A turban-like or soft adhesive dressing
is placed over the incision.
The bone flap is replaced and secured to
the skull with tiny plates and screws.
What happens after surgery?
After surgery, you are taken to the
recovery room where vital signs are monitored
as you awake from anesthesia. The breathing
tube (ventilator) usually remains in place until
you fully recover from the anesthesia.
Next, you are transferred to the neuroscience
intensive care unit (NSICU) for close observation
and monitoring. You are frequently asked
to move your arms, fingers, toes, and legs.
A nurse will check your pupils with a
flashlight and ask questions, such as
"What is your name?" You may experience
nausea and headache after surgery; medication
can control these symptoms. Depending on the
type of brain surgery, steroid medication (to control brain
swelling) and anticonvulsant medication (to
prevent seizures) may be given. When your condition stabilizes,
you’ll be transferred to a regular room
where you’ll continue to be monitored
and begin to increase your activity level.
The length of the hospital stay varies, from only 2–3 days
or 2 weeks depending on the surgery
and development of any complications.
When released from the hospital, you’ll
be given discharge instructions. Stitches or
staples are removed 7–10 days after surgery
in the doctor’s office.
- After surgery, headache pain is managed
with narcotic medication. Because narcotic pain
pills are addictive, they are used for a limited
period (2 to 4 weeks). Their regular use may
also cause constipation, so drink lots of water
and eat high fiber foods. Laxatives (e.g., Dulcolax,
Senokot, Milk of Magnesia) may be bought without
a prescription. Thereafter, pain is managed
with acetaminophen (e.g., Tylenol) and nonsteroidal
anti-inflammatory drugs (NSAIDs) (e.g., aspirin;
ibuprofen, Advil, Motrin, Nuprin; naproxen sodium,
- A medicine (anticonvulsant) may be prescribed
temporarily to prevent seizures. Common anticonvulsants
include Dilantin (phenytoin), Tegretol (carbamazepine),
and Neurontin (gabapentin). Some patients develop
side effects (e.g., drowsiness, balance problems,
rashes) caused by these anticonvulsants; in
these cases, blood samples are taken to monitor
the drug levels and manage the side effects.
- Do not drive after surgery until discussed
with your surgeon and avoid sitting for long
periods of time.
- Do not lift anything heavier than 5 pounds
(e.g., 2-liter bottle of soda), including children.
- Housework and yardwork are not permitted
until the first follow-up office visit. This
includes gardening, mowing, vacuuming, ironing,
and loading/unloading the dishwasher, washer,
- Do not drink alcoholic beverages.
- Gradually return to your normal activities.
Fatigue is common.
- An early exercise program to gently stretch
the neck and back may be advised.
- Walking is encouraged; start with short walks
and gradually increase the distance. Wait to
participate in other forms of exercise until
discussed with your surgeon.
- You may shower and shampoo 3 to 4 days
after surgery unless otherwise directed by your
- Sutures or staples, which remain in place
when you go home, will need to be removed 7
to 14 days after surgery. Ask your surgeon or
call the office to find out when.
When to Call Your Doctor
If you experience any of the following:
- A temperature that exceeds 101º F
- An incision that shows signs of infection,
such as redness, swelling, pain, or drainage.
- If you are taking an anticonvulsant, and
notice drowsiness, balance problems, or rashes.
- Decreased alertness, increased drowsiness,
weakness of arms or legs, increased headaches,
vomiting, or severe neck pain that prevents
lowering your chin toward the chest.
The recovery time varies from 1 to 4 weeks
depending on the underlying disease being treated
and your general health. Full recovery may take
up to 8 weeks. Walking is a good way to begin
increasing your activity level. Start with short,
frequent walks within the house and gradually
try walks outside. It’s important not
to overdo it, especially if you are continuing
treatment with radiation or chemotherapy. Ask
your surgeon when you can expect to return to
What are the risks?
No surgery is without risks. General complications
of any surgery include bleeding, infection,
blood clots, and reactions to anesthesia. Specific
complications related to a craniotomy may include:
- swelling of the brain, which may require
a second craniotomy
- nerve damage, which may cause muscle paralysis
- CSF leak, which may require repair
- loss of mental functions
- permanent brain damage with associated
What are the results?
The results of your craniotomy depend on the
underlying condition being treated.
Sources & links
If you have more questions, please contact
Mayfield Brain & Spine at 800-325-7787 or 513-221-1100.
biopsy: a sample of tissue
cells for examination under a microscope to
determine the existence or cause of a disease.
burr hole: a small dime-sized
hole made in the skull.
cerebrospinal fluid (CSF): a clear fluid produced by the choroid plexus in the ventricles of the brain that bathes the brain and spinal cord giving them support and buoyancy to protect from injury.
craniectomy: surgical removal
of a portion of the skull.
craniotome: a special saw
with a footplate that allows cutting of the
skull without cutting the dura mater.
craniotomy: surgical opening
of a portion of the skull to gain access to
the intracranial structures and replacement
of the bone flap.
dura mater: the outer protective
covering of the brain.
endoscopic-assisted surgery: a procedure using a probe (endoscope) fitted with a tiny camera and light, which is inserted through a small keyhole craniotomy to remove a tumor.
laser: a device that emits
a narrow intense beam of energy to shrink and
lesion: a general term that
refers to any change in tissue, such as tumor,
blood, malformation, infection or scar tissue.
minimally invasive surgery: use of technology (e.g., endoscopes, cameras,
image-guidance systems, robotics) to operate
through small, keyhole incisions in the body.
image-guided surgery: use
of preoperative CT or MRI scans and a computer
workstation to guide surgery.
otologic surgeon: a doctor
who specializes in surgery of the ear.
oculoplastic surgeon: a doctor
who specializes in surgery of the eye and face.
skull base surgeon: a doctor
with special training to perform complex craniotomies
at the base of the skull.
seizure: uncontrollable convulsion,
spasm, or series of jerking movements of the
face, trunk, arms, or legs.
shunt: a drainage tube to
move cerebrospinal fluid from inside the ventricles
of the brain into another body cavity (e.g.,
stroke: a condition caused
by interruption of the blood supply to the brain;
may cause loss of ability to speak or to move
parts of the body.
stereotactic: a precise method
for locating deep brain structures by the use
of 3-dimensional coordinates.
ultrasonic aspirator: a surgical
tool that uses a fine jet of water, ultrasonic
vibration, and suction to break up and remove
updated > 4.2016
reviewed by > Ron Warnick, MD, Mayfield Clinic, Cincinnati, Ohio
Mayfield Certified Health Info materials are written and developed by the Mayfield Clinic. We comply with the HONcode standard for trustworthy health information. This information is not intended to replace the medical advice of your health care provider.