Chiari malformation

What are Chiari malformations?

A Chiari malformation is a condition in which a part of the brain, called the cerebellum, bulges through a natural opening at the base of the skull and into the spinal canal. Normally, the cerebellum sits above this opening.

About 1 in 1,000 people have a Chiari malformation. Most were born with the condition, although in rare cases it develops later in life due to an injury, disease or infection. Some patients have no symptoms, and the malformation is discovered accidentally when they have a medical imaging test for another concern.

Chiari malformations may interfere with the normal flow of cerebrospinal fluid (CSF) between the brain and spinal cord. This can cause a harmful buildup of CSF in the brain (a condition called hydrocephalus) or the spinal cord.

At UCSF Benioff Children's Hospitals, our pediatric neurosurgeons are experts in procedures to treat Chiari malformations and related conditions.

Types of Chiari malformations

There are different types of Chiari malformation:

• Type 1 Chiari malformation. This is the most common type. In type 1, the lower part of the cerebellum (called the cerebellar tonsils) extends through the natural opening in the skull. Type 1 usually goes undiagnosed until adolescence or adulthood.
• Type 2 Chiari malformation. In this type – also known as an Arnold-Chiari malformation – cerebellum and brain stem tissues bulge into the natural opening. Type 2 occurs most often in children with myelomeningocele, a form of spina bifida (a birth defect that affects the spine). It's also the type most commonly associated with hydrocephalus. The symptoms of type 2 are generally worse than those of type 1.
• Type 3 Chiari malformation. This type is rare but can be life-threatening. In type 3, parts of the cerebellum, brain stem and sometimes the surrounding membranes push through an opening in the back of the skull. Babies with type 3 often have other serious birth defects.

Symptoms of Chiari malformations

Symptoms vary widely from child to child. Some children don't have symptoms or develop them later in life.

Symptoms of a Chiari malformation may include:

• Coordination problems
• Difficulty swallowing, speaking or breathing
• Dizziness
• Double vision or blurred vision
• Fatigue
• Headache (especially after coughing, sneezing or straining)
• Hearing problems
• Insomnia
• Mental impairment
• Muscle weakness or numbness
• Neck pain
• Occasional sharp pain in or near the eyes
• Paralysis of the arms and legs
• Problems with fine motor skills (tasks that require hand and wrist movement, such as picking up toys or drawing)
• Rapid involuntary downward eye movements
• Scoliosis
• Sleep apnea
•  Vomiting

Diagnosis of Chiari malformations

Your child will be evaluated thoroughly to look for signs of Chiari malformation and to rule out other conditions that might be causing their symptoms.

The evaluation will include questions about your child's medical history as well as your family's medical history. If your child's pediatrician has sent any records, we'll review this information. Be sure to tell the pediatric neurologist about any medications your child is using, including over-the-counter medicines, vitamins, nutritional supplements or herbal remedies.

Your child's evaluation probably will include an MRI scan. This noninvasive imaging test helps us determine the extent of the malformation. The doctor may also order a test called CSF flow imaging to evaluate how well the cerebrospinal fluid flows between the skull and spine.

If your child has certain issues, such as impaired coordination and sensory loss, other tests may be performed.

Treatment of Chiari malformations

Treatment depends on the type of Chiari malformation and the patient's symptoms. If your child has no symptoms and their day-to-day life is unaffected, they may only need monitoring (regular assessments) by a doctor.

If treatment is needed, the pediatric neurologist will work with your child's primary care doctor to design a treatment plan that meets your child's needs. The plan may include more than one kind of treatment. You also may be referred to additional doctors or other medical professionals.

The most common surgical treatment for Chiari malformation is called a posterior fossa decompression. In the procedure, the surgeon enlarges the opening in the back of the skull to create more space for the cerebellum. The goals are to relieve pressure within the skull and restore the normal flow of cerebrospinal fluid.

The team may also recommend surgical treatment for any associated conditions your child has, such as hydrocephalus, myelomeningocele or a tethered spinal cord.

The medical team will explain any risks or possible complications. Don't hesitate to ask your child’s doctors, nurses and therapists any questions you have. If the treatment plan includes medication, be sure your child takes it exactly as instructed.

Remember to keep all of your child's follow-up appointments.