Patient education: Chiari malformations (The Basics)

What are Chiari malformations? — 

Chiari malformations, or "CMs," are problems in which the lower part of the brain extends into the space around the spinal cord.

There are 3 main types of CM:

●Type I, or "CM-I" – This is the most common type. Part of the "cerebellum," which is the lower back part of the brain, bulges through the normal opening at the bottom of the skull (figure 1). Normally, only the spinal cord passes through this opening. Most of the time, CM-I is not found until a person is a teen or adult, when it starts causing symptoms.

●Type II, or "CM-II" – The cerebellum and brain stem do not grow normally. This type is found before or soon after birth. It most often happens in babies born with a condition called "spina bifida."

●Type III, or "CM-III" – This is the most severe type, and is rare. It is found before or soon after birth. Babies born with this type have an extra, abnormal hole in the back of their skull that part of the brain pushes through.

It is not known exactly what causes CMs. Most of the time, it seems to be related to the way the skull, brain, and spinal cord develop before birth.

What are the symptoms of a CM? — 

The symptoms depend on the type of CM.

Many people with CM-I never have any symptoms. But some people start having symptoms as a teen or adult. This is often related to pressure on the brain and nerves. In some people, a fluid-filled cyst forms on the spinal cord. This can also cause symptoms.

Symptoms of CM-I can include:

●Pain in the back of the head or neck, especially after coughing or straining

●Voice changes

●Speech or swallowing problems

●Trouble walking

●Sleep apnea, which is when the person stops breathing for short periods during sleep

●An abnormal curve in the spine, called "scoliosis"

●Pain, weakness, or numbness in the arms or legs

CM-I can also cause "hydrocephalus" in children. This is when there is too much fluid in the brain. It can cause symptoms like headache, vomiting, and behavior changes.

Babies and children with CM-II can have trouble swallowing, weakness, and trouble breathing. As they grow, they often develop hydrocephalus.

CM-III is rare but serious. Many babies born with this do not live very long. Those who do often have problems like intellectual disability, seizures, and trouble controlling their muscles.

Is there a test for CMs? — 

Yes. The main way doctors find CMs is with an imaging test called "MRI." This create pictures of the inside of the body. It can show if part of the brain extends into the space around the spinal cord. CM-I is sometimes found when a person gets an MRI for another reason.

Other tests that can find CMs include:

●CT scan – This is another type of imaging test.

●Ultrasound – Sometimes, a CM can be seen on an ultrasound before a baby is born.

People with CM-I who have symptoms of sleep apnea might get a test called a "sleep study." For the study, you are hooked up to different machines while you sleep. The machines monitor your heart rate, breathing, and other body functions.

How are CMs treated? — 

Treatment depends on the type of CM and whether it is causing symptoms.

Some people with CM-I do not need treatment if they have no symptoms. In this case, doctors will do regular exams and MRIs. This way, they can watch for any changes over time.

Doctors usually recommend surgery for people with CM-I who have any of these:

●Symptoms caused by pressure on the brain

●A fluid-filled cyst in the spinal cord

●A blockage in the flow of fluid through the spinal cord

Surgery usually involves removing some of the bone in the back of the skull. This eases pressure on the brain. Some people need a "shunt." This is a device that helps drain the extra fluid from the spinal cord.

CM-II and CM-III can also sometimes be treated with surgery. People with these types of CM might need treatment for other problems, too.

When should I call the doctor? — 

If you or your child has a CM, call your doctor or nurse for advice if:

●Your symptoms get worse.

●You get new symptoms like worsening headache, pain, weakness, numbness, or trouble with speech or swallowing.

More on this topic

Patient education: Obstructive sleep apnea in adults (The Basics)
Patient education: Obstructive sleep apnea in children (The Basics)
Patient education: Spina bifida (The Basics)
Patient education: Hydrocephalus in babies and children (The Basics)

Patient education: Sleep apnea in adults (Beyond the Basics)