Chiari malformation is a disease in which the lower part of the brain extends down into the spinal canal. Common symptoms include headaches, balance problems, and sleep issues.
If you have a Chiari malformation, you may have questions about how to treat it.
Our experts at the offer the most advanced treatments to help bring your symptoms under control.
On this page:
What Is Chiari Malformation?
The cerebellum is the lower part of your brain. It normally rests just above the large opening in the base of your skull, called the foramen magnum.
In people with Chiari malformation (CM), the lower part of the cerebellum, called the tonsils, herniates or bulges out below the foramen magnum. As a result, the tonsils block the normal flow of the cerebrospinal fluid (CSF) in the brain. The abnormally located tonsils also put pressure on the spinal cord.
Most cases of Chiari malformation are congenital, meaning a person is born with it. The most common cause is a malformed or overly small posterior aspect of the skull.
With high-resolution imaging, doctors diagnose CM in 1 out of every 1,000 people in the U.S., but very few ever have symptoms. Doctors refer to Chiari malformation without symptoms as Chiari syndrome.
What are the types of Chiari malformation?
There are a few types of CMs:
Chiari malformation type 1
In type 1, part of your cerebellum drops through the normal foramen magnum opening.
The cerebellum is the part of the brain that controls:
- Balance.
- Coordination.
- Motor learning.
- Vision, including eye movements.
Type 1 is the most common — and mildest — kind of Chiari malformation. This type may form while the skull and brain are growing. Symptoms may not occur until the teen or adult years.
Doctors often find type 1 during exams for other health issues. Most people with type 1 don't have any symptoms.
Chiari malformation type 2
Type 2 occurs in babies who are still growing inside their mothers' wombs. In this type, the cerebellum and brain stem both push through the normal opening to the spinal canal.
The brain stem, which is crucial for life, controls many body processes, such as:
- Breathing.
- Blood pressure.
- Heart rate.
- Sleep.
- State of consciousness.
Type 2 occurs with a type of spina bifida called myelomeningocele. In this condition, the spine doesn't close properly before birth. Doctors diagnose this form of CM while their mother is pregnant or shortly after they’re born.
Chiari malformation type 3
In type 3, the most severe form, the skull contains an abnormal opening. Part of the cerebellum and/or brain stem passes through this opening.
This form of Chiari malformation causes serious and even life-threatening issues.
CM type 3 is very rare. As with type 2, parents tend to receive their child's type 3 diagnosis before birth.
How common is Chiari malformation?
It’s estimated that slightly less than one in 1,000 people will have the condition. Most cases are asymptomatic. CM is detected most often when people have diagnostic imaging for unrelated issues.
What causes Chiari malformation?
Doctors don’t know exactly what causes Chiari malformation, but most cases appear to be congenital, meaning that the person was born with the brain and spinal cord defect, and that it developed while they were a fetus. This type is called primary CM.
However, some forms of Chiari malformation may be associated with prior brain trauma, infection, or disease. This type of CM is called acquired or secondary CM.
Chiari malformation risk factors
Doctors can't yet predict who might be born with or develop Chiari malformation. These malformations might run in families, but the research is still in its early stages.
Some studies suggest CMs affect women more often than men.
What Are the Signs and Symptoms of Chiari Malformation?
Many people with CM type 1 seen on imaging will never get symptoms. When symptoms start in a person who has type 1, they can range from mild to severe.
Headaches are the most common symptom of type 1. They're often in the back of the head.
Headaches typically occur after:
- Changing positions.
- Coughing.
- Laughing.
- Lifting heavy objects.
- Sneezing.
- Straining.
Other symptoms include:
- Blurry or double vision.
- Feeling dizzy.
- Memory problems.
- Numbness or tingling in the hands or feet.
- Sleep apnea.
- Tinnitus or ringing in the ears.
- Trouble swallowing.
Some people with CM also develop syringomyelia, a rare disorder that causes a syrinx, or cyst, to develop in the spinal cord. As the cyst grows, it can damage the spinal cord and cause symptoms that may range from mild to severe, depending on its size and location.
Symptoms, which often begin in early adulthood, include:
- Headaches.
- Inability to feel hot or cold.
- Pain and weakness in the arms, back, legs, or shoulders.
When should I see a doctor about my Chiari malformation symptoms?
If you have any of these symptoms, talk to your doctor about them.
How Do You Diagnose Chiari Malformation?
Your doctor will get your history and perform a complete physical exam, which may suggest Chiari malformation type 1.
Next, your doctor will order imaging to get a detailed look at your brain and spinal cord.
UPMC experts often order one or more of these tests:
How Do You Treat Chiari Malformation?
Once your doctor confirms a Chiari malformation type 1, the next key step is to learn if it causes symptoms. Some people with type 1 don't have any symptoms (Chiari syndrome). In that case, your doctor will want to observe you over time.
Close to 90% of people with Chiari type 1 will remain asymptomatic, even if they have syringomyelia.
Muscle relaxants and NSAIDs can be used to relieve headaches and neck pain if they develop.
Surgical options
People diagnosed with Chiari type 1 by imaging who have symptoms may need surgery. It's the only treatment that can improve the symptoms.
Posterior fossa decompression
The most common surgery for Chiari malformation type 1 in adults is posterior fossa decompression.
In this surgery, neurosurgeons:
- Remove a small section of bone from the back of the skull.
- Open the tough sac that covers and protects the brain (the dura).
- Place a permanent, waterproof patch to provide extra room. The extra room relieves pressure on the brain and lets the CSF flow freely again.
Most people stay in the hospital one to two days.
Because UPMC neurosurgeons care for many people with Chiari malformations, they've refined their techniques.
But complications may still arise, such as:
- CSF leaks.
- Infections.
- Partial paralysis.
- Swallowing problems.
- Stroke.
- Spine instability.
Surgery may also fail to relieve all your symptoms.
Why Choose UPMC for Chiari Malformation Care?
UPMC has the largest neurosurgery department in the U.S. People come from around the world to see our experts for care.
Each neurosurgeon is highly specialized and is an expert in a small number of highly complex techniques. They care for many people with your same health issue. In general, the more often a surgeon does a certain surgery, the better their results and safety record.
Plus, UPMC provides complete care to people with complex health issues.
Neurosurgeons, neurologists, ENT surgeons and specialists, and other providers work as a team to combine care throughout your stay.
