Chiari Malformation

A Chiari malformation (CM) happens when brain tissue in the lower back of your skull goes into your spinal canal. A structural problem with your skull typically causes it. Nearly all CM cases are present at birth (congenital). But you might not know you have it until later in life.

With CM, the base of your brain — your cerebellum — goes downward into an opening in your skull called the foramen magnum. This opening sits above your spine and spinal cord. CM can lead to pressure on your cerebellum and other nerve structures. It can also block the flow of cerebrospinal fluid (CSF). CSF helps protect your brain and spinal cord.

Healthcare providers classify Chiari malformations into types based on how much they affect the back of your brain. The types increase in severity and include:

• CM type 0: There are little to no parts of your cerebellum in the foramen magnum. But there’s crowding at that level.
• CM type 1: The lower parts of your cerebellum (the cerebellar tonsils) go into the foramen magnum. This is the most common type of Chiari.
• CM type 1.5: Your cerebellum and part of your brainstem go into the foramen magnum. Providers consider type 1.5 a progression of type 1.
• CM type 2: Your cerebellar vermis, brainstem and fourth ventricle (a fluid-filled cavity) are compressed. It usually happens with myelomeningocele, a severe form of spina bifida.
• CM type 3: Some of your cerebellum and brainstem extend through an abnormal opening in the back of your skull (not the foramen magnum). This is called an encephalocele.
• CM type 4: Your cerebellum is underdeveloped or has parts missing. It’s also known as cerebellar hypoplasia.

Your cerebellum helps with functions like movement, balance and breathing. CMs cause symptoms related to these functions. Treatment depends on the severity and may include surgery.

Symptoms of Chiari malformation

You may have no symptoms with CM. And specific Chiari malformation symptoms vary based on the type. But in general, they include:

• Headaches or intense pain in the back of your head or neck that get worse after coughing or sneezing
• Developmental delays (in babies and children)
• Balance and coordination issues
• Dizziness
• Hearing and vision issues
• Weak muscles
• Sleeping issues

These issues can affect your mood. You may be at a higher risk of depression.

Chiari malformation type 0

CM type 0 is rare. Symptoms may happen if a fluid-filled cyst (syrinx) forms inside your spinal cord. You may have:

• Balance problems or trouble walking
• Headaches
• Muscle spasms or tightness
• Numbness or tingling

Chiari malformation type 1

This is the most common type. You may not know you have CM type 1 until adolescence or adulthood. Many people don’t have symptoms. But some people develop:

• Severe head and neck pain, including headaches at the base of your skull (most common)
• Loss of pain and temperature sensation in your upper torso and arms
• Arm and hand weakness
• Episodes of muscle tightness (spasticity)
• Dizziness and balance problems
• Double or blurred vision and sensitivity to bright light
• Ringing in your ears and hearing loss
• Sleep apnea

Symptoms may look different in infants and children. They may include:

• Difficulty feeding, which may lead to a lack of growth
• Excessive crying and irritability
• Nighttime waking
• Reaching for their head and neck (due to pain)

Chiari malformation type 2

CM type 2 almost always happens alongside myelomeningocele. This occurs when your baby’s backbone and spinal canal don’t close before birth. You may get this diagnosis during pregnancy and/or your baby’s healthcare provider may notice symptoms shortly after birth.

This type is associated with other conditions and complications, like:

• Tethered cord syndrome
• Syringomyelia
• Hydrocephalus
• Lower cranial nerve dysfunction

CM type 2 causes a range of symptoms due to these related complications. They may include:

• Weak or absent cry
• Changes in your baby’s breathing pattern, like pauses in breathing (apnea)
• Uncontrolled neck and back arching (opisthotonos)
• Rapid downward eye movements
• Swallowing issues and a weak gag reflex
• Face and arm weakness

Chiari malformation type 3

CM type 3 is very rare. It involves an encephalocele — a condition where brain tissue grows through an opening in a newborn’s skull. The symptoms and complications can range in severity. Severe cases often lead to death. Symptoms may include:

• Seizures
• Buildup of fluid in their brain (hydrocephalus)
• Mental and physical developmental delays

Chiari malformation causes

Differences in skull structure often cause Chiari malformations. These differences typically happen during fetal development due to a gene change. You may inherit the gene change from your biological parent(s). Or it may happen randomly after conception. There’s nothing you can do to prevent Chiari malformation. It can affect anyone.

This condition almost always develops during fetal development. So, it’s present at birth (congenital). But you may not develop symptoms until later in life.

Very rarely, Chiari malformations can develop at some point after birth. In these cases, your skull might change shape due to:

• A brain tumor or cyst
• A buildup of blood or fluid in your brain
• Increased pressure in your skull

Complications

Chiari malformation can cause severe health issues and developmental delays. Complications and related conditions may include:

• Hydrocephalus: This life-threatening condition occurs when CSF builds up in your brain. It causes pressure within your skull.
• Syringomyelia and hydromyelia: When CSF doesn’t flow properly between your brain and spine, it can build up in your spine. This can damage your spinal cord.
• Tethered cord syndrome: Children with myelomeningocele are at an increased risk of developing tethered cord syndrome. This occurs when their spinal cord attaches to their spine due to scarring after closure surgery.

In addition, symptoms of a Chiari malformation can affect your mood, especially if you have insomnia or severe headaches. Some people may develop depression. If this condition affects your mood, talk to your healthcare provider or a mental health professional.

How doctors diagnose this condition

Imaging tests of your brain are the main way healthcare providers diagnose Chiari malformations. But to start, your healthcare provider will ask about your symptoms. They’ll do a physical and neurological exam.

Imaging tests may include:

• MRI
• Cine MRI (to see the flow pattern of cerebrospinal fluid)
• CT scan
• X-ray

A provider may spot a CM with imaging tests you get for other reasons.

In some cases, a provider may see a Chiari malformation in a fetus during a pregnancy ultrasound.

How is it treated?

Your healthcare provider will make a treatment plan based on your symptoms. The goal of treatment is to support normal CSF flow and protect your brain and spinal cord from further damage.

If you don’t have symptoms, you likely don’t need treatment. Instead, your provider will recommend regular imaging tests to check whether it’s getting worse.

Treatment for mild symptoms may include:

• Pain medications, like NSAIDs
• Massage therapy or physical therapy
• Limiting physical activities like heavy lifting
• Hearing aids or glasses to help with hearing or vision issues

Chiari malformation surgery

Severe Chiari malformation cases may need surgery. In general, surgery helps relieve pressure on your brain and/or improve CSF flow. Procedures may include:

• Posterior fossa decompression: Your surgeon removes a part of the back of your skull (posterior fossa). It’s the most common surgery.
• Laminectomy: Your surgeon removes a small portion of the bones covering your spinal column.
• Duraplasty: Your surgeon opens the dura (a membrane on the outside of your brain). Then, they sew in a patch to make the membrane larger.
• Electrocautery: Your surgeon applies electricity to a small part of your brain called the cerebellar tonsils. The procedure shrinks this tissue without causing brain or nerve damage.
• Shunt placement: Your surgeon implants a tube (shunt) in your skull to drain excess CSF if you have hydrocephalus.

Each of these procedures has potential risks and complications. Your care team will explain them.

What can I expect?

The outlook varies depending on the severity and type of Chiari malformation. CM type 1 often has a good outcome. Surgery helps improve symptoms in many cases.

Chiari type 2 and 3 can range in severity. A common complication of these types is hydrocephalus, a buildup of cerebrospinal fluid. It can be life-threatening.

It’s important to work closely with your care team. They can help monitor your symptoms and determine the right treatment plan for you or your child.

Life expectancy

If you have mild or no symptoms after a Chiari malformation diagnosis, you’ll likely have a normal life expectancy. Severe symptoms and certain types of Chiari malformation can be fatal. Talk to your healthcare provider about what to expect after a diagnosis.