A keyhole craniotomy is a type of brain surgery where doctors create a very small opening in the skull to reach the brain. The name "keyhole" comes from the small size of the opening. This technique is less invasive than traditional surgery and helps reduce damage to healthy parts of the brain.

Keyhole craniotomy is used to treat different conditions in the brain. These include tumors, aneurysms, arteriovenous malformations, and blood clots. It's also used to help treat epilepsy or take samples of tissue from the brain. Keyhole craniotomy may be an option when the area needing treatment can be safely reached though a narrow opening in the skull.

While every surgery has risks, keyhole craniotomy generally is safe and risks are minor. The procedure requires specialized instruments and surgical expertise.

Most people spend a few days in the hospital after keyhole craniotomy. Recovery can take a couple of weeks. You usually can return to light activities sooner with keyhole craniotomy than with traditional brain surgery.

Types of keyhole craniotomy

There are different types of keyhole craniotomy. The type of keyhole craniotomy depends on the location of the area to be treated.

• Supraorbital craniotomy. The surgeon makes a small cut in or above the eyebrow to reach the front of the brain. This surgery is often used for tumors or aneurysms near the skull base or behind the eyes.
• Retrosigmoid craniotomy. This approach uses a small opening behind the ear to reach the back of the brain near the brainstem. It's commonly used to treat tumors such as acoustic neuromas and conditions such as trigeminal neuralgia.
• Minipterional craniotomy. This is a version of the traditional open craniotomy pterional approach, where the keyhole opening is made near the temple. It allows access to the side and base of the brain and is used for tumors, aneurysms or bleeding.
• Endoscopic endonasal approach. This approach goes through the nose to reach the skull base. It's often used for pituitary tumors or growths in the center of the skull. It doesn't require cuts on the face or head and doesn't require removing part of the skull.
• Transorbital craniotomy. A small cut is made in the eyelid or around the eye to reach the front of the brain. This type usually is used for tumors near the eye or in the front of the skull.
• Interhemispheric craniotomy. A small opening is made in the top of the skull near the midline to reach deep areas between the two halves of the brain. It's usually used for cysts or tumors in the center of the brain.
• Suboccipital craniotomy. A small cut is made at the base of the skull to reach the back of the brain. It's often used to treat tumors in this area or Chiari malformation.
• Burr hole craniotomy. A small burr hole is made in the skull and the lesion is removed through this small opening. Typically done for tumors within the brain. Can also be done with placement of a tube that allows for resection within the tube.

A keyhole craniotomy is done to treat or diagnose several types of brain conditions while avoiding damage to nearby healthy brain tissue. This procedure allows surgeons to reach specific areas of the brain using a small "keyhole" opening in the skull rather than needing to remove a large piece of skull.

Keyhole craniotomy usually is used to:

• Remove a brain tumor. All or part of a tumor may be removed to relieve symptoms, reduce pressure and prevent complications. Tumors may be cancerous or noncancerous. Keyhole craniotomy may be used to remove skull base tumors, which grow at the base of the skull and may press on nerves or blood vessels. Tumors that may be treated with keyhole craniotomy include:
  • Meningiomas. These are tumors from the brain's protective linings.
  • Acoustic neuromas. Also called vestibular schwannomas, these are tumors that develop on the nerve that controls hearing and balance.
  • Metastatic brain tumors. These tumors have spread to the brain from another part of the body.
  • Gliomas. These tumors start within the brain or spinal cord.
• Treat blood vessel conditions. These include aneurysms and arteriovenous malformations (AVMs) that may bleed or cause a stroke.
• Remove a blood clot. Blood clots can block blood flow to the brain or cause bleeding inside the brain.
• Treat epilepsy. Through keyhole craniotomy, surgeons can reach the specific area of the brain where seizures start. The surgery can reduce the frequency and severity of seizures by methods such as removing or disconnecting that area of the brain.
• Perform a biopsy. A small sample of brain tissue may be collected and studied in a lab to help diagnose a tumor or neurological condition.
• Clip a cerebral aneurysm. A bulging or weakened blood vessel may be clipped to prevent it from bursting. Applying a small metal clip to the aneurysm stops blood flow to the bulging area.
• Relieve nerve pressure. Conditions such as trigeminal neuralgia or hemifacial spasm can be treated by moving blood vessels away from the nerve to reduce pain or twitching.
• Repair a tegmen defect. If there is a hole in the thin bone between the brain and ear, called a tegmen defect, keyhole surgery can repair it and stop cerebrospinal fluid from leaking into the ear.

When compared with traditional craniotomy, keyhole craniotomy can offer these benefits:

• Less damage to healthy brain tissue due to the small opening in the skull.
• Shorter recovery time, often with faster and less painful healing.
• Lower risk of complications, such as infection or bleeding.
• Less scarring because of the smaller cut needed.

Who is a good candidate for keyhole craniotomy?

Keyhole craniotomy may be an option if:

• The treatment area is near the surface of the brain. Keyhole surgery works best when the surgeon can reach the area without going through deep brain tissue.
• The treatment area is small or medium sized. Tumors, clots and cysts of this size can often be removed or biopsied through a small opening.
• Seizures have a clear focal point. If seizures are caused by a brain lesion that's clearly visible and in a spot that's reachable with keyhole techniques, keyhole craniotomy may be an option.
• You are in overall good health. People who can safely undergo anesthesia and heal after surgery may be good candidates for keyhole craniotomy.

Your neurosurgical team will use brain imaging, such as MRI or CT scans, to decide if a keyhole approach is safe and likely to be successful for your specific condition. If the affected area is too deep, too large or in a hard-to-reach spot, another type of surgery may be recommended instead.

Keyhole craniotomy is a minimally invasive brain surgery. It has several benefits compared with traditional approaches, such as smaller cuts, less damage to healthy tissue and quicker recovery times. However, like all surgical procedures, it carries potential risks and complications.

Common risks of keyhole craniotomy

• Bleeding and blood clots.
• Infection, including meningitis or infection of the incision.
• Cerebrospinal fluid (CSF) leak.
• Seizures.
• Changes in movement, speech or vision.

Less common risks of keyhole craniotomy

• Stroke.
• Brain swelling.
• Fluid on the brain.
• Changes in thinking and memory.
• Anesthesia risks, such as allergic reactions, breathing problems, nausea and vomiting, or low blood pressure.

Before your surgery, your healthcare team wants to make sure your body is as healthy as it can be. This helps lower the chances of problems during or after the operation.

Tests before keyhole craniotomy

• Medical history. Your care team asks about your past health, surgeries, allergies, and any medicines or vitamins you take.
• Neurological exam. You may have tests of your balance, memory, vision and speech before surgery. This helps your healthcare team learn what's typical for you so the team can identify any changes after surgery.
• MRI or CT scan. These imaging tests create pictures of your brain and help the surgeon plan the surgery.
• Blood tests. These check for signs of infection and how well your blood clots. They also check the chemical levels in your body, such as salts, sugars, hormones and other important elements that help your brain, heart and muscles work properly. If any of these levels are too high or too low, your care team may need to fix them before surgery to reduce the risk of complications.
• Heart and lung tests. You may need a heart test called an electrocardiogram or ECG. Or you may need a chest X-ray. These tests help the care team know whether your heart and lungs are healthy enough for surgery.

Medicine changes before keyhole craniotomy

Some medicines need to be stopped before surgery because they can cause bleeding or other concerns. These may include:

• Blood thinners and NSAIDs such as ibuprofen and naproxen. These usually are stopped several days before surgery.
• Vitamins and supplements. Some, such as fish oil or garlic pills, can affect bleeding. Tell your healthcare professional everything you take even items you can buy without a prescription.
• Steroids or seizure medicine. If you need these, your healthcare professional tells you how to take them before and after your surgery.

Before your keyhole craniotomy, it's helpful to know what happens during a typical procedure. Most people need to stay in the hospital for a few days after surgery. You are asleep for the procedure, and when you wake up, your care team monitors you closely. You should plan for someone to drive you home and stay with you for a little while after you leave the hospital.

Before keyhole craniotomy

On the day of your surgery, you follow a few important instructions to help your procedure go smoothly. Your healthcare team gives you detailed instructions ahead of time. Here's what you usually can expect:

• Follow your healthcare professional's recommendations on food, drink and medicines. You likely need to stop eating and drinking at midnight the night before surgery. This is to keep your stomach empty and reduce the risk of problems with anesthesia. Take only the medicines your healthcare professional tells you to take on surgery day. Bring a list of all the medicines you take, including vitamins and supplements.
• Follow your healthcare professional's instructions on bathing ahead of your surgery. You may be asked to shower the night before and again the morning of surgery using a special soap. This helps reduce the chance of infection.
• Remove jewelry and makeup. Don't wear any jewelry, nail polish, makeup or contact lenses on the day of surgery.
• Bring a support person. Ask someone to come along and drive you to the hospital and stay with you on surgery day. This person may be able to wait in a designated area or get updates during the procedure.

Before surgery, it's common to meet with the surgeon and the other members of your healthcare team to go over the plan and answer any questions you may have.

In most cases, you do not need your entire head shaved for a keyhole craniotomy. Surgeons usually shave only a small area around the incision site to keep the area clean and reduce the risk of infection. The rest of your hair is left untouched and can often cover the shaved spot as it grows back.

If your procedure is planned near your hairline or forehead, the surgeon may make the incision in a way that helps hide the scar in the natural hairline.

During keyhole craniotomy

You usually lie on an operating table for a keyhole craniotomy. The position you're in during surgery depends on where in your brain the surgeon needs to reach. For many keyhole craniotomies, such as those near the front of the brain, you may lie on your back. But for other areas, your head might be turned to the side, tilted slightly or positioned face down.

Your head is gently secured in place using a special headrest to keep it from moving during surgery.

You are given medicine by a needle in a vein in your arm that puts you in a sleeplike state during the surgery. This is called general anesthesia. You won't be aware or feel pain during the surgery.

During a keyhole craniotomy, a neurosurgeon carefully creates a small opening in your skull to reach the area of your brain that needs treatment.

First, the surgeon makes a small cut in the skin using a scalpel. Then, the surgeon uses a surgical drill to create the keyhole opening in the skull. This drill is very precise and gentle. It allows the surgeon to remove a small piece of skull without damaging the bone around it. This opening is the "keyhole."

The surgeon uses a microscope or an endoscope — a thin tube with a light and camera — to see clearly through the small opening. Specialized tools are passed through the keyhole to perform the surgery.

What happens next depends on why you're having the procedure:

• Tumor removal. The surgeon may remove it partially or entirely to relieve pressure and symptoms.
• Biopsy. The surgeon takes a small sample of tissue for testing.
• Clot removal. The surgeon carefully removes the clot to relieve pressure and prevent damage.
• Aneurysm clipping. For certain types of brain aneurysms, a small metal clip may be placed to stop blood from flowing into the weakened blood vessel.
• Epilepsy treatment. The surgeon may remove or disconnect the part of the brain where the seizures start.

Once the surgery is finished, the surgeon puts the piece of bone back in place and reattaches it. This is often with tiny plates or screws that stay under the skin. The skin is closed with stitches or staples and covered with a small bandage.

You then are taken to the recovery area, where your healthcare team monitors you as you wake.

After keyhole craniotomy

After keyhole craniotomy, you wake up in a recovery area where the care team watches you closely. You are connected to machines that check your heart, breathing and blood pressure. Most people stay in recovery for a few hours until they're fully awake.

You move to a hospital room, where you'll usually stay for 3 to 4 days. The length of your hospital stay depends on how you're recovering and what kind of surgery you had. Some people may need to stay longer.

You may feel tired or a little confused right after surgery. You may have a mild headache, nausea or swelling around the incision. These usually get better within a few days.

You may need medicines to help during recovery, including:

• Pain medicine to help with discomfort.
• Antiseizure medicine to lower the risk of seizures.
• Steroids to reduce swelling in the brain.
• Antibiotics to prevent infection.

Members of your care team help you get out of bed and start walking as soon as it's safe — usually within a day — to prevent blood clots.

You can go home when your pain is under control, you're eating and walking well, and your healthcare team says it's safe. You'll need someone to drive you home and stay with you for at least the first day or two.

Recovering at home

Healing takes time, and you recover at your own pace. Most people need 2 to 6 weeks to feel better, but recovery time can vary.

You may need help with cooking, cleaning or errands during the first week or two. It's important to rest and not overdo it. The brain can be sensitive to overactivity after surgery. Rest and taking it easy help lower the chance of swelling, headaches, fatigue and complications.

The care team tells you how to care for your incision. You may need to keep it dry for a few days and watch for signs of infection such as warmth, drainage or swelling at the incision site. You may notice a change in skin color. This may be a shade of red, purple or brown depending on your skin color.

Activity restrictions and recommendations may include:

• Light walking to help with circulation and energy, if your healthcare professional says it's safe for you.
• Avoiding heavy lifting, bending or straining for a few weeks.
• Avoiding driving until your healthcare professional says it's safe to do so.
• Planning for time away from work or school while you recover. Consider the type of activity you do on a daily basis. Some people are ready in 2 to 3 weeks, but others may need longer.

Some symptoms — such as headaches, tiredness or memory changes — may continue for a while as your brain heals. Most of these improve over time, but some people may need rehab or follow-up care.

You have a checkup with your surgeon, often a week or two after surgery. You also may need more scans or tests depending on the reason for your surgery. Follow-up imaging, such as an MRI or CT scan, may be done to show how the brain is healing and whether the surgery was successful.

The results of your keyhole craniotomy depend on the reason you had the surgery.

• Tumor removal. Your surgeon tells you whether your tumor was fully or partially removed. Even if some tumor remains, taking out part of it can still reduce symptoms. Your healthcare professional may discuss whether you need any more treatments such as radiation or chemotherapy.
• Biopsy. The tissue sample is sent to a lab to find out what type of tumor or mass you have. It may take several days to get results. These results help guide your next steps, such as whether you need more treatment.
• Clot or bleeding. Your healthcare team checks the imaging tests to confirm that the bleeding has stopped or that the clot is fully removed. You'll also be monitored closely for any signs of new bleeding or pressure in the brain.
• Seizure treatment. It may take some time to see if the surgery helped your seizures. You may still need seizure medicine after surgery, and your neurologist tracks your progress over time.
• Aneurysm clipping. Your healthcare team checked the imaging tests to make sure the clip is in the right place and the aneurysm is no longer receiving blood flow.

Your healthcare team explains what your results mean, what to watch for and what comes next, including any needed follow-up appointments.

Success rates and outcomes

Keyhole craniotomy has high success rates and positive outcomes for various conditions, including brain tumors, aneurysms and epilepsy. The specific results can vary depending on the reason for the surgery. But overall, people who have keyhole craniotomy have fewer complications and quicker recovery times than do people who have traditional open surgery.

• Tumor removal. Studies have found that keyhole approaches can successfully remove brain tumors in many cases. For example, a large 2022 study of people with skull base tumors reported that about 59% had complete or near-complete tumor removal using keyhole craniotomy. Study participants overall had few complications and returned home faster than those with traditional craniotomy.
• Aneurysm clipping. Research shows that keyhole craniotomy can successfully clip aneurysms in most cases, with many people experiencing good neurological results with few complications.
• Epilepsy treatment. In one large study, 87% of participants who had keyhole craniotomy to treat epilepsy were seizure-free more than six years after surgery. There were no reports of vision or speech problems, and no one needed another surgery. A few people had minor issues — such as temporary eye movement changes or facial weakness — that improved without treatment. The success of this treatment depends on finding where the seizure starts and safely reaching it through the keyhole approach.
• Recovery and quality of life. People undergoing keyhole craniotomy often benefit from shorter hospital stays, less pain and a faster return to daily activities.

Your neurosurgical team discusses the expected outcomes based on your individual condition and overall health.