What Happens During a Craniotomy: From Skin Incision to Replacing the Bone Flap

The consent form sits on the kitchen table next to a half-finished cup of tea. Somewhere in the second paragraph is a word that most people have only heard on television: craniotomy. The surgeon explained it well in clinic, but the details blurred the moment the conversation moved on to risks and dates, and now the questions arrive at 2 a.m. with nobody to answer them.

What happens during a craniotomy is, in truth, a sequence of ordinary steps performed with extraordinary care. Each stage has a purpose, a set of safety checks and a predictable rhythm. Knowing that sequence rarely makes the operation feel small, but it does make it feel less like a leap in the dark.

This explainer follows the operation from the first skin marking to the moment the bone is fixed back in place, then looks honestly at risk, recovery and the questions worth asking before the day itself.

What happens during a craniotomy, in one plain walk-through

A craniotomy is an operation in which a piece of the skull is temporarily removed so the surgeon can reach the brain, then put back at the end. The removed piece is called the bone flap. That single sentence contains the whole shape of the procedure: open, work, close.

Once you are asleep (or, for a small group of operations, lightly sedated and later woken), the team positions your head and holds it still. A strip of hair may be shaved along the planned incision. The surgeon cuts through the scalp and gently folds it back, then uses a high-speed drill to make one or more small holes in the skull. A fine cutting tool connects those holes, freeing a window of bone that is lifted away and kept sterile on the table.

Beneath the bone lies the dura mater, a leathery membrane that wraps the brain. The dura is opened and folded aside, and the actual work begins: taking a tumor sample or removing it, placing a tiny clip across an aneurysm (a weak bulge in an artery), draining a blood clot, or treating another problem the imaging has shown. Depending on the target, this part can take anywhere from under an hour to many hours.

Closing runs the sequence in reverse. The dura is stitched, the bone flap is secured with small titanium plates and screws, and the scalp is closed with sutures or staples. Johns Hopkins Medicine describes this same open-work-close pattern as the standard structure of the operation, whatever the underlying reason for surgery. Most of the variation between craniotomies lies in the middle, not at the edges.

Who is usually offered a craniotomy, and who is asked to wait

Surgeons do not open the skull because a scan looks worrying. They do it when a problem inside the head is causing harm, is likely to cause harm soon, or cannot be diagnosed any other way, and when the expected benefit is judged to outweigh the risk of the operation itself.

The commonest reasons, listed across MedlinePlus and Johns Hopkins, include:

• Brain tumors, whether to remove them, reduce their size or take a tissue sample for diagnosis.
• Aneurysms and arteriovenous malformations, which are abnormal tangles of blood vessels prone to bleeding.
• Blood clots inside or around the brain, often after injury or a hemorrhagic stroke.
• Abscesses, skull fractures pressing on the brain, and certain forms of epilepsy that have not responded to medicines.
• Placement of devices such as deep brain stimulation electrodes, which need direct access to specific brain regions.

Who is asked to wait, or offered something else? People whose lesions are small, slow-growing and silent may be followed with repeat imaging instead. Some aneurysms can be treated from inside the artery using catheters passed up from the groin, a technique known as endovascular coiling, which the NHS describes as an alternative to surgical clipping for many patients. Certain tumors respond to focused radiation without any incision. And when a person is too frail for a long anesthetic, or when the problem sits in an area where surgery would cause more disability than the disease, the team may recommend against operating altogether.

None of these judgments are made from a checklist. They come from a multidisciplinary discussion, and the decision belongs to you and your treating team together.

Before the incision: anesthesia, positioning and the head frame

The operating room work starts long before the scalpel. General anesthesia is given through a vein, and a breathing tube is placed once you are unconscious. An anesthesiologist stays at your side for the whole operation, adjusting medicines, fluids and ventilation moment by moment.

Positioning matters more in brain surgery than in almost any other field. The head must be absolutely still, so it is usually fixed in a padded frame that grips the skull with three pins. You will not feel this; it is placed after you are asleep. The body is then turned and supported so gravity helps rather than hinders, with the target area facing upward and pressure points cushioned to protect skin and nerves during a long procedure.

Many teams now use image guidance, sometimes called neuronavigation. Your pre-operative MRI or CT scan is loaded into a computer, and small markers on the head frame let the system show, on a screen, exactly where a pointer sits relative to the scan. It works a little like a satellite navigation system for the skull, letting the surgeon plan the smallest opening that still reaches the target.

For operations near areas that control movement, sensation or speech, electrodes may be placed on the scalp or limbs to monitor nerve signals throughout. This is called intraoperative neuromonitoring. If a signal begins to weaken, the team is warned before permanent damage occurs. Johns Hopkins notes that such monitoring is a routine part of many modern craniotomies rather than an exceptional add-on.

Only when the frame, navigation and monitoring are all confirmed is the skin cleaned with antiseptic and the incision line drawn.

The skin incision and lifting the bone flap

The incision is planned to do two things at once: reach the target and hide the scar. Common designs run behind the hairline, along a natural crease, or in a gentle curve so the healed line falls where hair will cover it. A narrow strip of hair may be shaved along the path, but full head shaving is uncommon today.

The scalp is remarkably rich in blood vessels, which is why even minor head wounds bleed so freely. Surgeons control this with small clips along the cut edges and careful cautery. The skin and the thin layer of muscle beneath are then peeled back as a single flap and held open with retractors, exposing the smooth white surface of the skull.

Now comes the part that gives the operation its name. Using a high-speed drill with a guard that stops automatically when it breaks through, the surgeon makes one or several small openings called burr holes. Each is roughly the diameter of a fingertip. A different attachment, a craniotome, is then passed between the holes. It has a footplate that slides along the underside of the skull, lifting the dura away from the bone so the cutting edge above cannot touch the brain.

The freed piece of bone, the bone flap, is lifted out and placed in a sterile container or wrapped in a solution-soaked sponge on the instrument table. It is labeled and watched over for the whole operation. The edges of the opening are smoothed, and any bleeding from the bone itself is stopped with a paste that hardens quickly.

At this point the surgeon is looking at the dura, not the brain. The most delicate part is still to come.

Under the bone: the dura and the brain's own protection

The dura mater is the outermost of three membranes wrapping the brain and spinal cord. Its name is Latin for tough mother, and it earns the description: it is dense, fibrous and surprisingly strong for a layer thinner than a coin. Beneath it sit two finer membranes and the clear cerebrospinal fluid that cushions the brain like water around a boat.

Opening the dura is done slowly. The surgeon lifts a corner with a fine hook, makes a small cut, then extends it under direct vision so the brain surface beneath is never nicked. The membrane is folded back and stitched loosely to the scalp edge to keep it out of the way. The brain itself is now visible: pale, glistening, gently pulsing with each heartbeat.

A resting brain is not something to be pushed around. Surgeons work between its folds, along natural planes, and use gentle retractors padded with moistened cotton strips to hold tissue aside. Operating microscopes magnify the field many times, so blood vessels finer than a hair become clear and structures can be separated by fractions of a millimeter.

Brain swelling during surgery is a known concern. The anesthesiologist can lower it by adjusting the level of carbon dioxide in the blood, giving medicines that draw fluid out of brain tissue, or draining a little cerebrospinal fluid. These maneuvers give the surgeon a softer, slacker brain to work around, which reduces the need for firm retraction.

People are often surprised to learn that the brain itself has no pain receptors. That fact is the reason awake operations are possible at all, and it comes up again in a later section.

The work inside: what the surgeon actually does

Everything up to this point has been about access. What happens next depends entirely on why the operation was planned.

For a tumor, the surgeon identifies its edges, often with the help of neuronavigation, and removes it piece by piece using suction, fine instruments and sometimes an ultrasonic device that breaks tissue apart while sparing vessels. Samples go straight to a pathologist, who may give an initial read within the hour. The goal is to remove as much as can be taken safely, which is not always all of it; surgeons will leave tumor behind rather than damage tissue that controls speech or movement.

For an aneurysm, the task is to find the neck of the bulge and place a small spring-loaded titanium clip across it, sealing it off from the artery while blood keeps flowing down the normal vessel. The NHS describes this clipping procedure as one of the two main treatments for a ruptured aneurysm, alongside endovascular coiling.

For a blood clot, the surgeon opens the collection and suctions or irrigates it out, then finds and stops the bleeding source. For epilepsy surgery, electrodes may first map exactly where seizures start before that area is removed. For device placement, the electrode or probe is guided to its target using coordinates calculated from the scan.

Throughout, the neuromonitoring team reports. If the signals for hand movement dip while the surgeon is working near the motor cortex, work pauses and the approach is adjusted. Hemostasis, the careful stopping of all bleeding, is checked and rechecked before anyone thinks about closing. A brain that bleeds after the skull is sealed has nowhere for the blood to go.

Awake craniotomy: why some people are woken up mid-operation

The phrase sounds like a horror film, and it is worth being precise about what it actually involves. An awake craniotomy is a craniotomy in which the patient is roused from sedation for a portion of the operation so the surgeon can test brain function in real time. Mayo Clinic describes it as an option when a tumor or seizure focus lies close to areas that control language, movement or vision.

The logic rests on that earlier fact: the brain has no pain fibers. The scalp, skull and dura do, so these are thoroughly numbed with local anesthetic and the opening is done under sedation. Once the brain is exposed, sedation is lightened. You become aware, comfortable and able to talk, but your head remains fixed and you cannot see the operating field.

A neuropsychologist or speech therapist then sits at your side and asks you to name pictures, count, read, or move a hand. Meanwhile the surgeon touches tiny areas of the brain surface with a low-current probe. If touching a spot makes you stumble over a word, that spot is marked and protected. The map that emerges shows exactly where it is safe to remove tissue and where it is not.

Once the mapping and the resection near critical areas are complete, sedation is deepened again for closure. Mayo Clinic notes that most people remember little of the awake portion and report that it was less distressing than they feared.

Awake surgery is not offered to everyone. It requires the ability to cooperate calmly for a sustained period, a lesion in a location where mapping adds real information, and a team practiced in the technique. Your surgeon and anesthesiologist decide together whether it is appropriate.

Closing up: bone flap replacement, plates and stitches

Closure is unhurried. A rushed close risks bleeding or fluid leaks that undo hours of careful work.

The dura is sewn back together with fine sutures. Where the membrane has shrunk or been removed, a patch is used: sometimes tissue borrowed from the scalp lining, sometimes a synthetic or processed collagen sheet. The aim is a watertight seal, because cerebrospinal fluid leaking through the skin later is a route for infection. Some surgeons run a small layer of sealant over the stitch line for extra security.

Bone flap replacement follows. The flap that has waited on the table is returned to its window and fixed with small titanium plates and screws, or with low-profile clamps that grip both edges. Johns Hopkins describes these fixation devices as permanent and safe to leave in place. Titanium does not set off airport scanners in most cases and is compatible with MRI. The small gaps left by the burr holes are often filled with bone chips or a paste that gradually integrates with the skull.

Over months, the bone knits at the edges. The flap does not need to fuse fully to be stable; the plates hold it firmly from the day of surgery.

Finally the scalp flap is laid back, the muscle layer is stitched, and the skin is closed with sutures or staples. A soft drain may be left under the scalp for a day or so to prevent fluid pooling. A light dressing goes on, the head frame comes off, and the anesthesiologist begins waking you up, usually in the operating room so the team can check that you move all limbs and follow simple commands within minutes of emerging.

Craniotomy vs craniectomy: when the bone stays out

People often confuse two words that differ by a handful of letters. A craniotomy replaces the bone at the end of the operation. A craniectomy removes the bone and deliberately leaves it out, either for weeks or permanently.

Why would anyone leave the skull open? Because a swelling brain inside a rigid box has nowhere to go. After severe head injury, a large stroke or certain infections, pressure inside the skull can climb to levels that squeeze off blood supply. Removing a large section of bone gives the brain room to swell outward instead of inward. The bone flap is either stored (in a freezer or, in some centers, in a pocket under the skin of the abdomen) or discarded and later replaced with a custom-made implant. The operation to put bone or implant back, months later, is called a cranioplasty.

Feature	Craniotomy	Decompressive craniectomy
Bone flap at end of surgery	Replaced and fixed	Left out
Typical purpose	Access to treat a lesion	Relief of dangerous brain swelling
Usual setting	Planned or urgent	Usually emergency
Second operation needed	Not for the bone itself	Yes, cranioplasty later
Head shape after surgery	Normal contour	Soft or sunken area until cranioplasty

There is also a middle ground. During a planned craniotomy, if the brain is more swollen than expected, a surgeon may choose to leave the flap out rather than force it back. That decision is made in the moment and explained to family afterward. Knowing the vocabulary means the conversation lands less like a shock.

The words themselves signal intent, not severity. A small craniotomy for a biopsy and a large one for a tumor share a name but little else.

How serious is craniotomy surgery? Risks in honest terms

Any operation that opens the skull is major surgery. That should be said plainly. It is also one of the most rehearsed and monitored procedures in medicine, and the risk for a given person depends far more on what is being treated, and where, than on the act of opening the skull.

MedlinePlus and Johns Hopkins list the recognized complications. General risks shared with any operation include bleeding, infection, blood clots in the legs or lungs, and reactions to anesthesia. Risks specific to brain surgery include:

• Swelling of the brain in the days after surgery.
• Seizures, which is why anti-seizure medicines are sometimes prescribed around the operation; whether and for how long is a decision for your team.
• Stroke caused by injury to a blood vessel.
• Leakage of cerebrospinal fluid through the wound.
• New or worsened problems with speech, movement, vision, memory or balance, which may be temporary or lasting depending on the area involved.
• Infection of the bone flap, which occasionally requires its removal.

How likely is each? No honest single figure exists. A biopsy of a lesion near the brain surface carries a very different profile from removal of a tumor wrapped around the brainstem, and a planned operation in a well person differs from an emergency in someone already unconscious. Your surgeon will quote risks that apply to your operation, your anatomy and your health, and you are entitled to ask for those numbers directly.

What reduces risk is well established: careful pre-operative imaging and planning, neuromonitoring where relevant, meticulous stopping of bleeding, early mobilization afterward, and prompt attention to warning signs. None of these guarantee a smooth course. Together they make one far more likely.

Craniotomy recovery time: the first days and weeks

Recovery has a shape, and knowing it in advance takes some of the fear out of the fog.

The first night is usually spent in an intensive care or high-dependency unit. Nurses will wake you repeatedly to check that you can move your limbs, answer questions and follow commands. Those checks are tedious and reassuring in equal measure; they are how a developing problem is caught early. A headache is expected and is managed by the team. Facial swelling, especially around the eye on the operated side, often peaks two or three days in and then settles.

MedlinePlus notes that people typically stay in hospital for several days after brain surgery, with the exact length depending on the operation and how quickly walking, eating and thinking return to baseline. Physical, occupational and speech therapists may assess you before discharge and arrange follow-up if any function needs work.

At home, fatigue dominates the first few weeks. Concentration tires quickly, noise feels louder, and a short walk can call for a nap. This is normal healing, not a setback. Stitches or staples are removed when your team judges the wound ready, and a follow-up scan is often arranged to check the operated area.

Common restrictions in the early weeks, drawn from MedlinePlus discharge guidance, include no driving until cleared, no heavy lifting or straining, no contact sports, and no submerging the wound until it is fully healed. Alcohol is usually discouraged while medicines are being adjusted.

Full recovery is measured in weeks for a straightforward operation and months for a complex one. The bone flap edges take longer still to knit, but the plates hold it stable from the start, so there is no period when the skull is unprotected.

What people often get wrong about craniotomies

Some beliefs about brain surgery are so widespread that they deserve correcting one by one.

“They will shave my whole head.” Most teams shave only a narrow strip along the incision, and many incisions are planned to hide within hair. Full shaving is now the exception.

“The bone is thrown away.” In a craniotomy the bone flap is always replaced. Only in a craniectomy, done for swelling, is it left out, and even then it is usually stored for later replacement or substituted with a custom implant.

“My skull will be weak forever.” Titanium plates hold the flap firmly from day one, and the bone edges knit over months. Johns Hopkins describes the fixation as permanent, and there is no ongoing need to avoid touching or lying on the area once the wound has healed.

“Awake surgery means feeling the operation.” The scalp and skull are fully numbed, the brain has no pain receptors, and Mayo Clinic notes that most people recall the awake portion as far less distressing than they expected.

“Brain surgery changes who you are.” Personality change can happen when a lesion or the operation involves the frontal lobes, but it is not a general consequence of opening the skull. Most people report themselves, and are reported by family, as unchanged in character. Fatigue, irritability and low mood in the early weeks are common and usually fade.

“If they cannot remove it all, the operation failed.” Surgeons often stop short deliberately to protect function. Partial removal can relieve pressure, secure a diagnosis and make other treatments more effective. The plan is set before surgery, and a subtotal removal that was planned is a success, not a failure.

“Metal in my head means no MRI.” Standard titanium fixation is MRI-compatible. Always tell the radiology team you have had surgery, but do not assume scanning is off the table.

Questions to ask your care team

A good consultation leaves you with fewer questions, not more, but that only works if you bring the right ones. Writing them down beforehand helps; so does bringing someone who can listen while you absorb.

About the operation itself:

• What exactly are you trying to achieve, and what would count as a good result for me?
• Where will the incision run, and how much hair will be removed?
• Will neuromonitoring or navigation be used? Is an awake approach being considered, and why or why not?
• How long do you expect the operation to take, and who will update my family during it?

About risk and alternatives:

• What are the specific risks for my lesion and its location, in numbers you would apply to me?
• What are the alternatives, including watching and waiting, radiation or endovascular treatment, and why is surgery being recommended over them?
• What would happen if I chose not to have the operation?

About recovery:

• How long do you expect me to be in hospital, and where will I wake up?
• Which restrictions apply to me, and for how long? When might I drive, return to work, exercise or travel?
• Will I need therapy afterward, and how will that be arranged?
• What follow-up scans and appointments should I expect?

About medicines:

• Which of my regular medicines should I stop or continue before surgery, and who will tell me?
• Will I be given anti-seizure or steroid medicines, and how will decisions about tapering them be made?

Finally, ask who to call, and at what number, if something worries you after discharge. The answer to that question matters more than any other on the list.

When to call your doctor after a craniotomy

Most recoveries are uneventful, and most symptoms in the first weeks are the ordinary discomforts of healing. A few signs are different. They can point to bleeding, swelling, infection or fluid leak, all of which are far easier to manage when caught early, and they should prompt a call to your surgical team or an emergency visit without waiting for the next appointment.

Seek urgent care, using emergency services if severe, for any of the following:

• A new seizure, or a seizure pattern that has changed.
• Sudden or steadily worsening headache that is not eased by the medicines your team prescribed.
• New weakness, numbness or clumsiness in the face, an arm or a leg, or a new difficulty speaking or understanding speech.
• Increasing drowsiness, confusion, or difficulty staying awake, especially if others notice it before you do.
• Repeated vomiting, or a stiff neck with fever.
• Clear or straw-colored fluid leaking from the wound, nose or ear, which can signal a cerebrospinal fluid leak.
• Redness, swelling, warmth, pus or a gaping edge at the incision, or a fever without an obvious cause.
• New vision changes, double vision or loss of part of your visual field.
• Calf pain or swelling, or sudden breathlessness or chest pain, which may indicate a blood clot.

MedlinePlus lists these among the warning signs that warrant prompt medical contact after brain surgery. If you are unsure whether something counts, call anyway. Surgical teams would far rather hear about a false alarm than miss a real one, and the person on the other end of the phone will not think you are wasting their time.

Keep your discharge paperwork and the team’s contact number somewhere visible. In the moment, nobody wants to be searching for it.

Frequently asked questions

How serious is craniotomy surgery?

A craniotomy is major surgery that opens the skull under general anesthesia and carries real risks including bleeding, infection, seizures and stroke. Its seriousness for any individual depends far more on the underlying problem and its location than on the opening itself. A biopsy near the surface and removal of a deep tumor share a name but very different risk profiles; your surgeon will quote risks specific to your operation.

What is the survival rate after a craniotomy?

There is no single survival rate, because craniotomy is an access technique rather than a treatment, and outcomes are governed by the condition being treated. Survival after a planned biopsy, aneurysm clipping and emergency removal of a traumatic clot differ enormously. Guideline bodies do not publish one figure for this reason. Ask your surgical team for outcome data that applies to your diagnosis, age and general health.

How long does it take to fully recover from a craniotomy?

Craniotomy recovery time varies with the operation. MedlinePlus describes a hospital stay of several days followed by weeks of fatigue and gradual return to normal activity, with more complex operations or those involving neurological deficits taking months and often requiring rehabilitation therapy. The bone edges knit over months, but plates keep the flap stable from day one. Your team will set individual milestones for driving, work and exercise.

What can't you do after a craniotomy?

Early restrictions commonly include no driving until cleared by your team, no heavy lifting or straining, no contact sports, no swimming or soaking the wound until fully healed, and limited alcohol while medicines are being adjusted. MedlinePlus discharge guidance lists these as typical. Restrictions are lifted individually based on wound healing, seizure risk and how your specific operation went, so follow your own team’s timeline rather than a general one.

What is the difference between craniotomy vs craniectomy?

In a craniotomy the removed piece of skull is replaced and fixed at the end of the operation. In a craniectomy it is deliberately left out, usually to relieve dangerous brain swelling after injury or stroke, and is replaced or substituted with an implant months later in an operation called cranioplasty. The words describe what happens to the bone, not how large or dangerous the surgery is.

What is bone flap replacement and does the skull heal back?

Bone flap replacement is the final stage of a craniotomy, in which the removed skull piece is returned to its opening and secured with small titanium plates and screws or clamps. Johns Hopkins describes these fixation devices as permanent. The bone edges gradually knit over months, but stability does not depend on that; the plates hold the flap firmly from the day of surgery.

What is an awake craniotomy and does it hurt?

An awake craniotomy is one in which sedation is lightened after the skull is opened so the surgeon can test speech, movement or vision while working near those brain areas. It does not hurt because the scalp, skull and dura are numbed with local anesthetic and the brain has no pain receptors. Mayo Clinic notes most people remember little and find it less distressing than expected.

Will I be able to have an MRI with plates in my skull?

Yes, in almost all cases. Standard titanium plates, screws and clamps used to fix the bone flap are compatible with MRI scanning and rarely trigger airport metal detectors. Always tell radiology staff about your surgery so they can confirm the implant type, and carry any implant card you were given. Older or unusual devices are the exception, and your surgical team can tell you exactly what was used.

Will my personality change after brain surgery?

Not as a rule. Personality change is linked to lesions or operations involving the frontal lobes, not to opening the skull itself. Most people, and their families, report no change in character. Irritability, low mood, poor concentration and fatigue are common in the first weeks and usually fade as healing progresses. Persistent or marked changes should be raised with your team, since treatable causes such as swelling or medication effects may be responsible.

What are the alternatives to a craniotomy?

Depending on the condition, alternatives may include watchful waiting with repeat scans, focused radiation for some tumors, endovascular coiling for many aneurysms in which the vessel is treated through a catheter without opening the skull, and medicines for some forms of epilepsy. The NHS describes coiling and clipping as the two main options for ruptured aneurysms. Which route suits you is a multidisciplinary decision made with your treating team.

References

• MedlinePlus Medical Encyclopedia: Brain surgery
• NHS: Subarachnoid haemorrhage, treatment

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.