What is a Chiari malformation?
Chiari (pronounced “Key-ari”) malformation, also known as Arnold Chiari malformation, is a condition where a small portion of brain tissue from the lower back of the skull extends into the spinal canal. This occurs when the skull is smaller than expected, leaving limited space for the brain. As a result, part of the brain called the cerebellum pushes downward through the opening at the base of the skull, known as the foramen magnum.
Chiari malformation is most often congenital, which means it is present at birth. While Chiari malformation is rare, advancements in imaging technology have led to more frequent diagnoses during a woman’s pregnancy.
Types of Chiari malformation
Chiari malformations are most often present at birth. However, in rare cases, the condition can develop later in life due to injury, disease or conditions that cause excess fluid buildup in the skull. These are known as secondary or acquired Chiari malformations.
No matter when a Chiari malformation develops, doctors classify it into one of four types based on which parts of the brain extend into the spinal canal and the severity of the condition. This classification helps guide treatment decisions.
Chiari Malformation Type I
The most common form, Type I, happens when the lower part of the cerebellum (the part of the brain that controls balance and coordination) pushes into the opening between the skull and the spinal cord, known as the foramen magnum. Most people don’t have symptoms at first, and it’s often found incidentally during imaging tests for other conditions.
Chiari Malformation Type II
In Type II Chiari malformation, both the cerebellum and brainstem push downward into the spinal canal, where they normally do not belong. This type is almost always linked to a condition called myelomeningocele, a serious form of spina bifida that happens when the spinal cord and backbone don’t close properly before birth. Myelomeningocele often leads to weakness or paralysis below the affected area of the spine. Type II is also the type most often associated with hydrocephalus, which means a buildup of excess fluid in the brain.
Chiari Malformation Type III
Type III is a very rare and severe form that occurs when the cerebellum and parts of the brainstem extend through an opening in the back of the skull, forming a sac (called an encephalocele). This rare condition can cause significant neurological symptoms, such as seizures, developmental delays and physical disabilities.
Chiari Malformation Type IV
The rarest and most severe form, Type IV happens when the cerebellum doesn’t fully develop. Parts of the cerebellum may be missing or underdeveloped, which can lead to serious problems with brain function.
Chiari malformation symptoms
Not everyone with a Chiari malformation has symptoms. Some people may not notice side effects until later in life. Symptoms depend on several factors, including the type of Chiari malformation, how much the brain presses on the bottom of the lower skull, and whether it restricts the fluid that surrounds the brain and spinal cord, known as cerebrospinal fluid. When Chiari malformation symptoms occur, they may include:
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Head and balance problems
- Headaches, often triggered by coughing, sneezing or straining
- Dizziness or loss of balance
- Ringing in the ears (tinnitus)
- Vision changes, such as blurred or double vision
- Hearing loss
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Muscle and movement issues
- Weakness in the arms or legs
- Problems with coordination
- Scoliosis (curvature of the spine)
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Breathing, eating and speaking difficulties
- Trouble swallowing, gagging, or frequent choking
- Problems with breathing or sleep apnea
- Speech difficulties
- Drooling or frequent vomiting (more common in infants and children)
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Other possible symptoms
- Sleep problems, such as insomnia
- Depression
- Difficulty gaining weight in infants
- Heart palpitations
When to see a doctor
See your primary care doctor if you or your child experience any unusual symptoms. Your doctor can rule out other conditions and help determine whether a Chiari malformation could be the cause. If your doctor suspects this defect, they may refer you to a neurologist for a more detailed evaluation and specialized treatment.
Chiari malformation causes
A Chiari malformation happens when the lower part of the brain pushes down into the spinal canal, the space where your brain and spinal cord meet. This is caused by a structural issue in the brain and spinal cord, where the area that holds your cerebellum (the part of the brain that controls movement) is smaller than usual. This extra pressure causes the cerebellum to move to an unusual spot. This typically happens while babies are still developing in the womb.
The condition is often linked to a genetic change (mutation) inherited from your family, or it can happen randomly after conception. In very rare cases, a Chiari malformation can develop later in life, even if you weren't born with it. This can happen if there’s a change in the shape of your skull or spinal cord caused by:
- A brain tumor
- A cyst
- Blood buildup (hematoma)
- Fluid buildup in the brain (hydrocephalus)
- Increased pressure in the brain (intracranial hypertension or pseudotumor cerebri)
Sometimes, a Chiari malformation can also be seen alongside other health conditions like:
- Goldenhar syndrome
- Achondroplasia (a form of dwarfism)
- Connective tissue disorders like Ehlers-Danlos syndrome
- Spina bifida
Chiari malformation risk factors
Scientists are still learning what can increase the risk of a Chiari malformation. A Chiari malformation can affect anyone, but you're more likely to develop it if someone in your biological family has the condition.
Complications
In some people, a Chiari malformation may not cause any symptoms, and they may not need treatment. However, in others, the condition can worsen over time and lead to serious complications. These complications may include:
- Hydrocephalus: This occurs when too much fluid builds up in the brain, which can affect thinking and cause other issues. People with hydrocephalus may need a shunt, a flexible tube that helps drain the extra fluid to another part of the body.
- Spina bifida: This is a condition where the spinal cord or its protective covering doesn't fully develop. Part of the spinal cord may be exposed, leading to serious problems like paralysis. People with Chiari malformation Type II often have a type of spina bifida called myelomeningocele.
- Syringomyelia: Some people with Chiari malformation also develop syringomyelia, where a cyst or cavity (called a syrinx) forms in the spinal cord. As it grows, the syrinx can put pressure on the nerves, causing pain, weakness, and stiffness.
- Tethered cord syndrome: In this condition, the spinal cord becomes attached to the spine, causing it to stretch. This can lead to nerve and muscle damage, especially in the lower body.
How is Chiari malformation diagnosed?
To diagnose a Chiari malformation, your doctor will do a physical exam and check things like your memory, balance, coordination, reflexes and movement. They may also order imaging tests to confirm the diagnosis or to look for other conditions, such as fluid buildup in the brain (hydrocephalus) or bone abnormalities.
Medical history and exam
Your doctor will ask about any health conditions you have and how you’re treating them. They’ll also want to know about any conditions or disorders that run in your family and as much information as possible about your symptoms, including when they began, how often they occur, what they feel like and how they affect your ability to function. Your doctor will conduct a thorough exam of your physical health and may also want to test important indicators of neurological health, such as your reflexes, balance and motor skills. Problems with balance and other neurological functions may be signs of a Chiari malformation.
Imaging tests
Several imaging tests can provide valuable information about the condition of your brain and spinal cord and help your doctor make a diagnosis, including:
- Magnetic resonance imaging (MRI) scan: This type of imaging, which creates pictures using radio waves and magnets, is often the first imaging test providers order for diagnosing a Chiari malformation. An MRI can show how much of the cerebellum, if any, has entered the spinal canal.
- Computed tomography (CT) scan: Your provider may also order a CT scan to help rule out other potential causes of your symptoms, such as a brain tumor. A type of X-ray test, a CT scan can also show abnormalities in the skull and spine.
- X-ray: Your doctor may want you to have X-rays to look for problems with the bones at the bottom of your skull.
Chiari malformation treatment
Your doctor will develop a personalized treatment plan tailored to your specific needs, considering factors like the severity of your symptoms, how they affect your daily life and your personal goals. Not everyone with Chiari malformation needs treatment. If you don't have any symptoms, your doctor may recommend monitoring the condition with regular imaging tests. You and your doctor can always adjust your plan and start treatment if symptoms appear.
If your Chiari malformation causes symptoms, your doctor might suggest lifestyle changes, therapy or medications to help manage things like headaches. For more severe symptoms, surgery to create more space for the cerebellum or address related problems, like hydrocephalus, may be the most effective solution.
Lifestyle changes
Not everyone with Chiari malformation requires surgery, especially for mild symptoms. You might be able to manage your symptoms and improve your quality of life by adjusting your daily activities.
Some lifestyle changes for Chiari malformation include:
- Reducing symptom triggers: Avoiding heavy lifting, straining or intense physical activity can prevent increased pressure on the brain and spinal cord, which can lead to headaches and other symptoms.
- Using assistive devices: A cane can offer more stability when walking. Glasses can help with blurry vision, and hearing aids may improve symptoms like hearing loss.
Medication
Medications can’t treat a Chiari malformation, but they can help you manage pain and other symptoms. Your doctor may recommend prescription or over-the-counter medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), to help with pain relief.
Therapy
In addition to medications, therapy may help improve your quality of life. These treatments can reduce symptoms and help you manage daily activities more comfortably.
- Physical therapy: A physical therapist can teach you exercises to improve balance and reduce dizziness. They can also use techniques like manual therapy to help relieve joint pain.
- Massage therapy: This type of therapy can help relax muscles, reduce tension and improve circulation, which may ease pain or discomfort related to Chiari malformation.