What Is a Craniotomy?

If a surgeon needs to work on the brain itself, how do they get there? The brain sits inside the skull, sealed away behind bone — which is excellent protection day to day, and an obvious obstacle on the day something inside needs treating. A craniotomy is the operation that solves that problem: a neurosurgeon temporarily removes a section of skull, does the work the brain needs, and then puts that section of bone back. This page walks through the questions people usually ask, in roughly the order they ask them.

The short video at the top of this page, "Right Frontal Craniotomy Brain Surgery", shows a real example. In about a minute and a half it previews a University Hospitals Case Medical Center webcast in which the team removes a brain tumor — and the area of brain causing seizures — from an awake patient, using MRI scanning and brain mapping during the operation itself. Keep that case in mind as you read, because it touches on several of the answers below.

What exactly is removed — and is it put back?

Yes, it's put back — that's the defining feature. The surgeon makes an incision in the scalp, folds the skin aside, and removes a carefully planned piece of skull called the bone flap. Underneath lies the dura, the tough outer covering of the brain, which is opened to reach the brain itself. When the work is finished, the dura is closed, the bone flap is fixed back into place — usually with small plates and screws — and the scalp is stitched over it. In time the bone heals into the skull around it.

There's a closely related operation worth knowing by name, because the two are often mentioned together: a craniectomy. There, the bone flap is deliberately not replaced at the end of the operation — often because the brain is swollen and needs room, with the bone returned in a later operation once things have settled. A short 3D animation on this site, "Craniotomy and Craniectomy", walks through both operations side by side and shows the layers involved, from scalp and skull down to the coverings of the brain.

Why would someone need one?

A craniotomy isn't a treatment in itself — it's the doorway. What matters is what's on the other side of it. The common reasons include removing a brain tumor (our cancer condition hub gathers the site's wider cancer guides), clipping or repairing a weakened blood vessel such as an aneurysm — covered in our article on what an aneurysm is — and removing a blood clot or relieving pressure after bleeding or injury inside the skull. Some epilepsy operations use a craniotomy to remove the small area of brain where seizures start, when medicines haven't controlled them; our guide to what epilepsy is covers that background. A craniotomy can also be the route for taking a biopsy when a diagnosis can't be reached any other way, for treating an infection inside the skull, or for dealing with fluid and pressure problems of the kind described in our article on hydrocephalus.

In the anchor video's case, two reasons overlapped: a low-grade glioma — a type of brain tumor — sitting near the motor strip, the part of the brain that controls movement, and seizures that appeared to be coming from the same area. Removing the tumor carefully offered a chance to help with both problems at once.

How does the surgeon decide where to open?

Craniotomies are named for where the opening is made — a "right frontal" craniotomy, like the one in the video, goes through the front part of the skull on the right side. Before the operation, scans (usually MRI, sometimes CT as well) are used to map the problem area and plan the smallest opening that gives safe access to it. The aim is always to arrive at the target by the route that disturbs the least healthy brain — and, where the area does something important, like movement or speech, to know exactly where those functions live before anything is removed.

On the day, a patch of hair may be clipped where the incision will go, and the head is held steady in a padded holder so it doesn't move. A companion video on this site, "Right Frontal Craniotomy", previews the same University Hospitals case from a second listing — a middle-aged man whose seizures led to the scan that found the tumor.

What happens during the operation itself?

Most craniotomies are done under general anaesthetic: you're fully asleep, and the anaesthesia team monitors you throughout. Working through the planned opening, the surgeon removes the bone flap, opens the dura, and does the main task — removing a tumor, clipping an aneurysm, clearing a clot — often working under an operating microscope, since the structures involved are small and the margins matter. The team keeps track of the brain and the body's vital signs as they go. Once the task is complete, bleeding is checked carefully, the dura is closed, the bone flap is secured back in place, and the scalp is closed over it.

What is an "awake" craniotomy, then?

It sounds alarming, but it's a deliberate technique, used when the area being operated on sits close to parts of the brain that control speech or movement. The brain itself has no pain receptors, so with the scalp numbed and sedation adjusted for different phases, a patient can be comfortably awake for the key part of the operation. While awake, they may be asked to speak, count, or move a hand or foot, while the surgeon gently stimulates the brain's surface to map which areas do what. That live feedback helps the team remove as much of the problem as possible while steering clear of the areas the patient can't do without. The anchor video's case used exactly this approach, together with MRI scanning during the operation, because the tumor lay near the motor strip — the movement area — and the team wanted to know, moment by moment, where safe removal ended.

What happens afterwards?

You'll wake up in a recovery area or a specialist unit where nurses check you frequently — how alert you are, your pupils, limb movements, blood pressure — because the first hours after brain surgery are about close watching. A headache and tiredness are common, the scalp wound will be covered, and a scan is often done to check the result of the operation. How long you stay depends on what was treated and how you recover; many people are up, walking, and eating within a day or two, but brain surgery is never something to rush, and tiredness can linger for weeks after you get home.

The bone flap heals in place over time, the scalp scar usually ends up hidden by hair as it regrows, and follow-up appointments and scans track both your recovery and the condition that led to surgery. Contact your team promptly — or seek urgent care — if you develop a worsening headache, vomiting, drowsiness or confusion, weakness or speech difficulty, a seizure, fever, or fluid leaking from the wound, or if the wound becomes increasingly swollen or red. Those warnings aren't a prediction; they're the standard safety net every craniotomy patient goes home with.

References & further reading

• MedlinePlus — Brain surgery: https://medlineplus.gov/ency/article/003018.htm
• Johns Hopkins Medicine — Craniotomy: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/craniotomy
• American Association of Neurological Surgeons — Patient information: https://www.aans.org/patients

Frequently Asked Questions

Is a craniotomy the same as brain surgery?

Not quite — it's one part of many brain operations. Brain surgery is the broad term for any operation on the brain; a craniotomy is specifically the step where a section of skull is temporarily removed to reach the brain, and put back at the end. Some brain operations reach their target by other routes, such as through the nose, and don't involve a craniotomy at all.

Will the piece of skull grow back or be replaced with metal?

In a standard craniotomy your own bone flap is put back, held with small plates and screws, and it heals to the surrounding skull. You're not left with a hole, and the small hardware is usually not something you can feel day to day. The main exception is a craniectomy, where the bone is left out on purpose — usually to give a swollen brain room — and restored in a later operation.

How long does a craniotomy take?

It varies a lot, because the opening itself is only the beginning — most of the time is spent on the work underneath, whether that's removing a tumor, clipping an aneurysm, or clearing a clot, and on the careful closing afterwards. Your surgeon can give you a realistic estimate for your own operation; the honest answer is that straightforward and complex cases differ by hours.

Does an awake craniotomy hurt?

Patients are often surprised to learn that the brain tissue itself doesn't feel pain — it's the scalp and surrounding tissues that do, and those are numbed, with sedation used for the parts of the operation that don't need the patient awake and participating. Teams who offer awake surgery prepare patients carefully beforehand, and there's always an anaesthetist dedicated to comfort throughout.

Will my hair grow back over the scar?

Usually, yes. Only a strip of hair along the incision line is clipped, the rest is left alone, and as the clipped hair regrows the scar is typically covered. Right after surgery the area may be swollen and tender, and your team will tell you when you can wash your hair and how to care for the wound while it heals.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Educational only — this article is general information about craniotomy, not medical advice and not a diagnosis. Whether this operation, or any treatment, is right for you is a matter for your own neurosurgery team, who know your results and your history.