Chiari malformation is a group of defects affecting the brain and spinal canal. The skull may be too small or misshapen, causing the brain tissue to extend into the spinal canal.

It can cause pain, trouble swallowing, headache, and more.

If the condition does not cause a person any problems, they will not require treatment. However, if it is affecting them, a doctor can recommend treatment options ranging from medication to surgery.

Read more to learn about the different types of Chiari malformation, symptoms, how it is diagnosed, treatment options, and more.

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Chiari malformation is a condition where part of the brain tissue at the base of the skull pushes into the top of the spinal canal.

The condition is present from birth. However, not all people with Chiari malformation know that they have it. If they do not have symptoms, it can go unnoticed.

According to the American Association of Neurological Surgeons (AANS), slightly less than 1 in every 1,000 people have Chiari malformation. This is 0.1% of the population.

There are four different types of Chiari malformation.

Type 1

This is the most common form of the condition. People with type 1 usually experience symptoms in late childhood and adulthood.

They may have symptoms including:

  • neck pain
  • balance and coordination problems
  • dizziness
  • numbness

However, this type often causes no symptoms at all and is found incidentally later in life. For this reason, it is also called adult Chiari malformation.

Type 2

Type 2 is the second most common form of the condition and is also called classic Chiari malformation. In people with this type, a larger amount of tissue pushes into the spinal canal.

It often happens alongside a type of spina bifida called myelomeningocele. This condition affects the spinal membranes and nerves, resulting in the spinal canal and backbone not closing properly.

This type causes more severe symptoms than type 1, and it requires surgery. Some symptoms include:

  • difficulty swallowing
  • breathing changes
  • weakness in the extremities

Type 3

Type 3 is very rare and happens when a lower part of the brain protrudes through the back of the head or neck. Unfortunately, this type is usually fatal and is diagnosed at birth.

People with type 3 who survive infancy may experience:

  • neurological defects
  • seizures
  • developmental delays

Type 4

This is where the cerebellum, part of the back of the brain, is not fully formed. Type 4 is very rare and may result in parts of the spine and skull being visible.

Tragically, children who have this type do not often survive infancy.

The cause of Chiari malformation is unknown. It may be caused by a fetal developmental defect in the womb.

Sometimes, a person may develop Chiari malformation later in life. This is known as secondary, or acquired, Chiari malformation.

Although rate, this form of the condition occurs if a person loses an excess of spinal fluid from the lower back or thorax area. This may be due to injury, illness, or infection.

The following are some symptoms of Chiari malformation:

  • headache
  • neck pain
  • dizziness
  • swallowing or breathing problems
  • balance problems
  • weakness of the muscles
  • tinnitus and hearing problems
  • nausea
  • excessive vomiting or drooling
  • scoliosis
  • psychological concerns, including insomnia and depression
  • coordination difficulties

However, some people with the condition have no symptoms at all. This is especially true of those with type 1.

If a person has no symptoms, the condition can be tricky to diagnose.

In some cases, it may often only be identified when a person is tested for another health condition. A doctor may see Chiari malformation on an MRI scan and order further tests to confirm a diagnosis.

However, sometimes Chiari malformation can be diagnosed before a person is even born. Older research suggests that ultrasound in the second trimester may detect 70–90% of abnormalities in fetuses. It is usually not possible to diagnose type 1 at this stage. However, if a fetus has types 2, 3, or 4, it may be visible.

A 2019 review states that Chiari malformation is frequently misdiagnosed as another neurological or psychological condition. This is likely because symptoms can be generalized and linked to a wide range of more common disorders.

If a person’s Chiari malformation does not cause any symptoms, they may never need treatment. However, the condition would require regular monitoring by a doctor.

For people with painful headaches and neck pain, a doctor may be able to prescribe some pain management medication. If this does not resolve symptoms, they may recommend surgery.

Decompression surgery

The most common type of surgery to treat Chiari malformation is decompression surgery. This involves a surgeon opening up the base of the skull and removing small pieces of bone either from the skull or the top of the spine. It releases pressure and allows fluid to flow more freely.

However, this type of surgery is not always guaranteed to work.

It may ease some symptoms, especially headaches. In some cases, it may make symptoms worse or cause no change at all.

Hydrocephalus

This is another type of surgery that may help to treat Chiari malformation.

During this operation, a surgeon will place a small tube called a shunt. This helps drain excess fluid, relieving pressure in the skull. It deposits the extra fluid into the chest or stomach so the body can safely absorb it.

Some conditions frequently occur alongside Chiari malformation. They include:

  • Syringomyelia: This is a condition where a growth-containing fluid grows on the spinal cord. If not treated, this can result in spinal cord damage.
  • Spina bifida: This is where the spinal cord and backbone do not close properly.
  • Hydrocephalus: This condition causes a buildup of fluid that sits in the brain, and it can be fatal if a person does not get treatment.
  • Scoliosis: This condition is where the spine curves abnormally. It usually develops in children and adolescents.
  • Tethered cord syndrome: This is a condition where the spine attaches to and stretches the spinal cord, reducing flexibility. This can result in severe nerve and muscle damage in the lower body.
  • Sleep apnea: In some cases, sleep apnea can occur in people with Chiari malformation. Sleep apnea causes breathing disturbances during sleep, and a 2019 review suggests clinicians should test for this in children with Chiari malformation to allow for early diagnosis and intervention.

For individuals with type 1 or 2, symptoms are not usually life threatening. However, some complications can occur and they may require treatment.

Unfortunately, types 3 and 4 are often fatal.

Chiari malformation is a condition where part of the brain tissue enters the spinal cord.

There are four types of this condition. Types 3 and 4 are usually fatal. However, people with types 1 or 2 can go through life with minimal symptoms and may only find out if they have an MRI scan for another condition.