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Chiari Malformation Type I

Chiari Malformations: What You Need to Know

  • There are two main kinds of Chiari malformations.

  • Type 1 Chiari malformation symptoms and signs can show up in infants, children, teens or adults.

  • Type 2 Chiari malformation is associated with spina bifida and is present at birth.

  • Surgery can address symptoms such as headache, hydrocephalus, sleep apnea and others.

More Information About Chiari Malformation from Johns Hopkins Medicine

Dr. Mark Luciano

The Simple Gets Complicated

Mark Luciano, M.D., Ph.D., of Johns Hopkins’ Department of Neurosurgery talks about how to diagnose and treat Chiari malformations.

Watch now.

What is a Chiari malformation?

A Chiari malformation is a defect occurring in the back of the head where the brain and spinal cord connect. In most cases, a Chiari malformation is present at birth, but the problem can be acquired.

A part of the brain at the rear of the skull bulges through a normal opening (foramen magnum) in the skull where it joins the spinal canal.

Type 1

Type 1 Chiari malformations commonly go unnoticed until problems arise in the adolescent or adult years of life. Many people with a Chiari type 1 malformation have no symptoms and do not need medical intervention.

Type 2

Type 2 Chiari malformations are typically seen in infants who are born with open spina bifida, a neurological condition that causes a portion of the spinal cord and the surrounding structures to develop outside instead of inside the spine, before birth.


What causes a Chiari malformation?

The exact cause of a Chiari malformation is unknown but theories suggest that certain maternal exposures during pregnancy (listed below) may affect the normal growth of the fetus’s skull, brain or spinal cord, resulting in a Chiari type 2 malformation:

  • Exposure to hazardous chemicals/substances, including alcohol and certain prescription or illegal drugs

  • Gestational diabetes

  • Lack of proper vitamins and nutrients in the diet, especially folate

  • Infection

Signs and Symptoms of Chiari Malformations


Chiari malformations are associated with the formation of a syrinx, a fluid-filled pocket, or cyst, in the spinal cord. This condition also known as syringomyelia. As the cyst fills with cerebrospinal fluid, it expands, putting pressure on the spinal cord.

In some patients with a Chiari malformation, increasing pressure from a syrinx can affect neuromuscular function, causing limb weakness or difficulties with walking or breathing.

Some children will show signs of a spine syrinx, but others will not. In these situations, an MRI scan may be needed for a definite diagnosis.


In children younger than 16 whose spines are still growing, the presence of a syrinx can also be associated with the development of scoliosis, an abnormal, lateral (side-to-side) curvature of the spine.


Toddlers, children and teens with undiagnosed type 1 Chiari malformations may develop headaches, which are typically located at the back of the head and neck, and are often made worse by exertion.


Type 2 Chiari malformations can also be associated with hydrocephalus, a condition in which there is an obstruction of the flow of cerebrospinal fluid that is found inside of the ventricles (fluid-filled areas) inside of the brain.

The buildup of fluid causes the pressure inside of the head to increase and the child’s skull bones to expand to a larger-than-normal appearance.

Sleep Apnea

Sleep apnea is another problem that occurs in people with a Chiari malformation. This is a serious sleep disorder characterized by brief interruptions in breathing during sleep. A sleep study can confirm the presence of sleep apnea so a doctor can prescribe treatment.

Other Symptoms

Chiari malformation symptoms can also include:

  • Hoarseness

  • Difficulty swallowing

  • Rapid, side-to-side eye movements (nystagmus)

  • Muscle weakness, lack of balance or abnormal reflexes

  • Nerve problems, including paralysis

Chiari Malformation Diagnosis

Type 2 is identifiable at birth, but type 1 Chiari malformations can be subtle and not cause signs or symptoms until later in life.

Sometimes medical professionals will notice a type 1 Chiari malformation when a person is having imaging tests for other reasons. This is called an incidental finding. Even when the condition is diagnosed, many patients with a type 1 Chiari malformation do not require any intervention.

For a child or adult with Chiari malformation symptoms, a health care provider will take a detailed medical history and perform a physical exam. A referral to a specialist may be appropriate.

Imaging tests, such as an MRI scan to create detailed pictures of the skull, brain and spinal cord, are commonly used to confirm the diagnosis.

Treatment for Chiari Malformations

Chiari malformation treatment will depend on the patient’s symptoms, age, general health and the severity of the condition.


Observation may be all that is required in children or adults with type 1 Chiari malformations who are not experiencing symptoms. Observation may involve regular physical exams and MRI scans. Those showing signs of a syrinx but not experiencing symptoms may be monitored with regular MRI scans.


Neurosurgery for Chiari malformation is intended to relieve the pressure on the brain tissue at the junction of the skull and spine.

Depending on the severity of the child’s symptoms and the anatomical problems associated with the malformation, a pediatric neurosurgeon may raise or remove bone from the lower skull opening (foramen) and graft dural membrane to protect the tissues of the brain and spinal column.

If the protruding portion of the brain is blocking the flow of cerebrospinal fluid and causing hydrocephalus, additional procedures may be necessary to treat the fluid accumulation.

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