A Chiari malformation (CM) is a type of structural change that affects the lower part of the brain. It’s most often due to a congenital condition that affects the shape or size of the skull. Congenital means that it’s present from birth.

In CM, part of the cerebellum extends into the spinal canal. This can lead to increased pressure in this area, which affects the function of the cerebellum and brain stem. It also blocks the flow of cerebrospinal fluid (CSF).

Surgery is one of the main treatment options for CM. This article will explore the surgical options for this condition, what the procedure is like, and more.

Chiari malformation surgery illustrationShare on Pinterest
The goal of Chiari malformation surgery is to relieve pressure on the lower part of the brain. Medical illustration by Bailey Mariner

The most common type of surgery for CM is called posterior fossa decompression. This procedure creates additional space around the lower part of the brain, helping reduce pressure and relieve symptoms.

In this type of surgery, a surgeon will make a small incision in the back of the head. Then, they will remove a little bit of bone from the bottom of the skull. This is called a craniectomy and helps make more space in the area.

It’s also possible that the surgeon will remove part of the bone from the top of the spinal canal as well. This is called a spinal laminectomy.

A surgeon can also use electrocautery to create even more space, if necessary. This method uses heat to reduce the size of the cerebellar tonsils, which are often the part of the cerebellum that has extended into the spinal canal.

Additional procedures

CM is also associated with a variety of other medical conditions. As such, other types of procedures may be needed to address these as well:

  • Hydrocephalus: In hydrocephalus, CSF builds up in the brain and can lead to dangerous increases in pressure. Doctors treat this in a couple of ways:
    • shunting, in which a small tube is placed into the head to help drain excess CSF into the chest or abdomen, where the body naturally reabsorbs it
    • third ventriculostomy, where a small hole is made in one of the cavities of the brain, helping release trapped CSF
  • Myelomeningocele: Myelomeningocele is the most severe type of spina bifida. Surgery is needed to reposition the spinal cord and close the opening in the back of the spine. This is typically done while a child is still in the womb.
  • Syringomyelia: Syringomyelia is when a CSF-filled cyst forms in the spinal cord. It’s possible to drain these cysts by placing a shunt.
  • Tethered cord syndrome: In tethered cord syndrome, the spinal cord has attached to surrounding tissues and cannot move freely. The resulting tension can lead to nerve damage. An untethering procedure can help address this.

While CM is typically present from birth, many people do not develop symptoms until they’ve reached adulthood. At this point, the condition can be detected through imaging tests like MRI scans.

Not everyone who has CM needs to have surgery. If you don’t have symptoms, your doctor may just want to monitor your condition periodically. Milder headache and neck pain due to CM may be treated using medications instead of surgery.

When symptoms are more severe and interfere with daily activities, a healthcare professional may recommend surgery. Some examples of symptoms that CM may cause include:

The overall goal of surgery for CM is to reduce pressure on the brain and spinal cord. This helps ease symptoms and improve quality of life.

Posterior fossa decompression for CM happens in a hospital, and you will be under general anesthesia. That means that you’ll be asleep during the surgery.

After you are sleeping, the surgery can involve the following basic steps:

  1. A portion of hair will be shaved from the area where the incision will be made.
  2. Your head may be placed into a device called a head clamp, which helps keep your head steady during surgery. If this occurs, it will involve a series of small punctures to secure the clamp to your skull.
  3. A surgeon will make an incision at the back of your head or top of your neck.
  4. The surgeon will work to expose the bones at the base of your skull and the very top of your neck.
  5. They will perform the craniectomy, and if necessary, the spinal laminectomy or electrocauterization.
  6. The surgeon may open the dura, which is the protective layer around the brain stem and spinal cord. This completes the decompression.
  7. The surgeon will close the incision.

The total amount of time that the surgery takes depends on what exactly is being done. A 2016 study of children having CM surgery found that, on average, it took about 2.5 hours.

After surgery, you’ll be moved to a recovery room until you wake up. Healthcare professionals will use equipment to monitor things like your heart rate, blood pressure, and blood oxygen. They will gradually remove this equipment as your recovery progresses.

You’ll need to stay in the hospital for at least a few days after your surgery. A 2014 study noted average hospital stays of about 2 to 3 days, depending on the type of procedure.

Remember that your hospital stay may be longer if you have a more complex procedure or if you experience complications afterward.

It typically takes 6 to 8 weeks to recover from CM surgery. Yet your specific recovery time may vary, based on the exact type of procedure you had, your age and overall health, and whether you had any complications.

When you wake up, you’ll likely find your head wrapped in a bandage. This helps protect the incision site and can also prevent you from scratching at it during your recovery.

It’s also typical to have some symptoms like nausea, pain, or headache shortly after your surgery. The hospital staff will give you medications to help with these things.

You’ll probably be able to get up and start moving around the day after your surgery. But you’ll need to avoid any strenuous activities or heavy lifting until 3 to 4 weeks afterward.

When you’re able to leave the hospital, you’ll receive instructions on how to care for your incision, as well as how and when to take any prescribed medications. Be sure to follow these instructions carefully.

Your surgeon will want to follow up with you in 6 to 8 weeks after your surgery to see how your recovery is going.

As with any surgery, CM surgery comes with risks. Yet these are generally uncommon.

Some of the risks associated with CM surgery may include:

  • bleeding in or around the surgical site
  • infection, including meningitis
  • nerve damage
  • paralysis
  • stroke
  • CSF leakage
  • pseudomeningocele, where a bulge that contains CSF develops under the skin at the incision site
  • hydrocephalus
  • brain sag, in which part of the brain sags away from the skull, leading to severe headaches

Ask your doctor to discuss the various benefits and risks of surgery with you. You can then use this information to make an informed decision on how to move forward with treating your CM.

The cost of CM surgery can depend on many factors, including the:

  • exact type of procedure
  • specific surgeon who does the surgery
  • hospital where the surgery happens
  • type of insurance coverage you have

A 2021 study notes that the average cost of surgery for CM type I, the most common type of CM, was $13,716. The researchers also note that the cost was over $6,000 higher when the surgery happened in a children’s hospital.

If you’re ever unsure about what you may be responsible for paying, contact your insurance provider prior to scheduling your CM surgery. They can give you detailed information about what is and what isn’t covered.

Many CM surgeries have a good outlook. Yet this can depend on how severe your CM is. More severe types of CM generally have a poorer outlook.

Age may also play a role in outlook. For example, a 2017 study found that children and adolescents undergoing surgery for CM type I had a better outcome than both younger and older adults.

A small 2017 study of 10 people who had had CM surgery found that symptoms like headache, atypical sensations, and trouble with coordination and balance were effectively alleviated in most people.

After surgery, the researchers did note that some people developed new eye movement dysfunction. This didn’t cause noticeable symptoms or concerns for these individuals.

Not every person who has surgery for CM will experience complete relief of their symptoms. It’s also important to note that if nerve damage has already happened due to CM, surgery cannot reverse this.

It’s also possible that some people will need more than one surgery for CM and any associated conditions. Your doctor will follow your recovery and let you know what to expect.

Surgery is one of the main treatment options for CM. On a basic level, it involves the removal of bone from the back of the skull and sometimes the top of the spine in order to reduce pressure on the brain and spinal cord.

CM surgery can help to ease symptoms in many people. However, some people may find that certain symptoms continue after surgery. Additionally, it’s possible you may need more surgeries in the future.

Prior to scheduling your surgery, talk with your doctor about the different benefits and risks associated with the type of procedure being considered. They can help to give you an idea of what to expect.