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Chiari Malformations

The Division of Neurosurgery at Children’s National Medical Center is one of the leading destinations in the country for the treatment of children with Chiari Malformations. Children’s evaluates approximately 80 patients each year, and the Division has a wealth of experience in determining the optimal course of treatment given each patient’s condition.

What is a Chiari malformation?
A Chiari malformation, previously called Arnold Chiari malformation, is a congenital (present at birth) defect where the posterior fossa, the bony space at the base of the back of the head, is too small. This abnormality causes the cerebellum to be pushed downward, which can cause pain and affect neurologic function, such as balance and coordination. The condition is rare, affecting approximately 1 in 100 people, and can go undetected for years.

There are four types of Chiari malformations:
  • Type I malformations are those in which the tonsils of the cerebellum extend beyond the base of the skull, through the opening called the foramen magnum. This condition may go unnoticed until problems arise in the adolescent or adult years.
  • Type II malformations are those in which not only the tonsils, but the vermis of the cerebellum, the 4th ventricle, and medulla of the brainstem are displaced through the bottom of the foramen magnum.
    • Type II Chiari malformations are typically seen in infants who are born with spina bifida (specifically myelomeningoceles), a neurological condition that causes a portion of the spinal cord and the surrounding structures to develop outside the body.
    • This type of malformation, as part of the spina bifida spectrum, is commonly associated with a condition known as hydrocephalus, a condition in which there is an overproduction or lack of absorption of the cerebral spinal fluid (CSF) that is found inside of the ventricles (fluid-filled areas) inside the brain. The increased fluid causes the pressure inside of the head to increase and the skull bones to expand to a larger-than-normal appearance.
  • Type III malformations are those in which the structures mentioned in the Chiari II malformation, as well as the cerebellum itself, are displaced through the foramen magnum into the canal of the spine. Type III malformations are frequently associated with an opening through the bone and skin known as an encephalomeningocele. These are the most severe of the Chiari malformations and may not be
  • Type IV malformations are those in which the back of the brain fails to develop normally.
What causes Chiari malformation?
Although the exact cause of Chiari malformation is unknown, it is thought that a problem during fetal development may cause the abnormal brain formation. Chiari malformation may be caused by exposure to harmful substances during fetal development or associated with genetic problems or syndromes that may have a tendency to run in families.

Theories suggest that the following may predispose the fetus to problems that affect the normal development of the head during pregnancy:
  • Exposure to hazardous chemicals/substances
  • Lack of proper vitamins and nutrients in the diet
  • Infection
  • Prescription or illegal drug and alcohol consumption
What are the symptoms of a Chiari malformation?
Some patients do not experience any symptoms, and others experience symptoms differently. The following are the most common symptoms in infants and older children:
  • Headaches (typically with exertion)
  • Stiffness or pain in the neck or back of the head area
  • Rapid, back and forth, eye movement (called nystagmus)
  • Developmental delays
  • Poor feeding and swallowing
  • History of aspiration pneumonia
  • Nasally voice
  • Weak cry
  • Breathing problems
  • Decreased strength in the arms
The symptoms of Chiari malformation may resemble other conditions or medical problems. Very severe Chiari malformations may be life threatening. Always consult your child’s physician for a diagnosis.

How is a Chiari malformation diagnosed?
If a Chiari malformation occurs with other congenital (present at birth) defects, the diagnosis may be made at birth. Other times, the diagnosis is made after the onset of specific signs and symptoms, and after diagnostic testing. Frequently, the condition is found incidentally when performing diagnostic testing for other reasons.

The physician obtains a complete prenatal and birth history of the child and may also ask if there is a family history of any medical problems. The physician will also ask about developmental milestones, such as the age the child sat up, crawled, or walked because a Chiari malformation can be associated with other neuromuscular disorders. Developmental delays may require further medical follow up for underlying problems.

During the examination, a measurement of the circumference of the child's head is taken and compared to a scale that can identify normal and abnormal ranges.

Diagnostic tests that may be performed to confirm the diagnosis of a Chiari malformation include:
  • X-rays - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
  • Computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
  • Magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. This is the best study to evaluate both the severity of the Chiari, the flow of spinal fluid from the brain to the spinal cord, and the presence or extent of a syrinx, a cavity in the spinal cord that is filled with cerebrospinal fluid.
The neurosurgeons at Children’s National Medical Center approach treatment of a child with a Chiari malformation based on:
  • Child's age, overall health, and medical history
  • Extent of the condition
  • Type of condition
  • Child's tolerance for specific medications, procedures, or therapies
  • Expectations for the course of the condition
  • Parent’s opinion or preference
Medical management consists of frequent physical examinations and diagnostic testing to monitor the growth and development of the brain, spinal cord, skull, and backbones.

Surgery is required when symptoms are present, neurological functioning is disrupted, or if a syrinx if detected. A syrinx is a cavity in the spinal cord that is filled with cerebrospinal fluid. When necessary, Children’s neurosurgeons perform inpatient surgery to relieve increased pressure inside the head or neck area, drain excess cerebral spinal fluid from the brain and spinal cord by inserting a shunt. The goal is to address all symptoms and restore neurological function.

Parents are instructed to watch for any changes that may affect the child's neurological status, including the following:
  • Breathing problems
  • Degree of alertness
  • Speech or feeding problems
  • Problems walking
  • Uncoordinated movement
Life-long considerations for a child with a Chiari malformation:
The full extent of the problems associated with a Chiari malformation are usually not completely understood immediately at birth, but may be revealed as the child grows and develops. Children born with a Chiari malformation require frequent examinations and diagnostic testing by his/her physician to monitor the development of the head as the child grows. The medical team works hard with the child's family to provide education and guidance to improve the health and well-being of the child.

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Chiari Malformations - Departments & Programs - Children's National Medical Center