Chiari Malformation

The exact cause of Chiari malformations is unknown. Theories suggest that exposure to toxins (such as hazardous substances, drugs or alcohol) or poor nutrition during fetal development may play a role.

Chiari malformations are present in approximately 1 in 1,000 people. The condition is classified by the severity of the disorder and the parts of the brain that protrude into the spinal canal. There are four types of Chiari malformation:

• Type I. Type I is the most common form of Chiari malformation. A type I Chiari malformation only involves parts of the cerebellum pushing outside of the skull. Many people with this form of Chiari malformation have no symptoms. The condition often is discovered by coincidence, usually during a test for another condition. It is most often diagnosed in adolescence and adulthood. Between 30 and 50 percent of patients with type I Chiari malformations also have abnormalities at the base of the skull and spine. This includes compression of the spine into the skull, bony unions of the cervical vertebrae, cervical spina bifida and scoliosis.
• Type II. Type II Chiari malformation is associated with spina bifida. In type II Chiari malformations, parts of the cerebellum and brain stem extend into the foramen magnum. This condition occurs with myelomeningocele, a form of spina bifida where the spinal canal and backbone do not properly close before birth. When this happens, the spinal cord protrudes through the back in a sac-like opening. A myelomeningocele can cause partial or complete paralysis of the area below the spinal opening. Hydrocephalus (buildup of cerebrospinal fluid in the brain) also may be associated with type II Chiari malformations and myelomeningocele.
• Type III. Type III Chiari malformation is the most severe form. It occurs infrequently. The cerebellum, brain stem and parts of the fourth ventricle (a structure that contains cerebrospinal fluid) herniate (push out) through the foramen magnum and compress the spinal cord. This can be accompanied by an occipital encephalocele (large sac that contains brain tissue and protrudes from the back of the skull and neck). This type of Chiari malformation is associated with severe neurological deficits.
• Type IV. Type IV Chiari malformation occurs when the cerebellum is not completely developed (hypoplastia). Portions of the skull may be missing.

Many adults and children with Chiari malformations have no symptoms at all. Symptoms can vary by age group and be present alone or in combination.

Infants with any form of Chiari malformation may show these symptoms:

• Arching of the back
• Feeding problems
• Swallowing problems (choking and gagging)
• Aspiration of food into the lungs
• Vomiting
• Gastroesophageal reflux
• Breathing problems
• Stiff neck
• Arm weakness
• Developmental delay
• Inability to gain weight

Symptoms of type I Chiari malformation include:

• Severe head and neck pain
• Headache pain at the base of the skull
• Collapsing from muscle weakness
• Dizziness
• Balance problems
• Spasticity
• Blurred or double vision
• Sensitivity to bright lights

Symptoms of type II Chiari malformation include:

• Altered breathing
• Central sleep apnea
• Depressed gag reflex
• Involuntary rapid downward eye movements
• Loss of arm strength
• Scoliosis
• Headaches

Type III and type IV Chiari malformation is rare, and children who are born with these types often do not survive. Symptoms of type III and type IV Chiari malformation include:

• Severe neurological deficits
• Hydrocephalus
• Other severe birth defects

Chiari malformations may be associated with syringomyelia and hydromyelia. These disorders involve a buildup of cerebrospinal fluid that forms a cyst or cavity in the spinal cord. As the cyst (syrinx) grows, it can cause additional symptoms, including:

• Loss of pain sensations in the upper torso and arms
• Loss of hot and cold sensations
• Loss of muscle strength in the hands and arms

Diagnosis of Chiari malformation

If your child shows signs of a Chiari malformation, a neurosurgeon will evaluate him or her to make an accurate diagnosis.

Specialists with Riley at IU Health perform the following exams and tests to diagnose Chiari malformations:

• Computed tomography (CT) scan. This is an X-ray scan that combines cross-sectional images to create highly detailed pictures of the structures of the brain and spinal cord.
• Magnetic resonance imaging (MRI). MRI combines radio waves and a magnetic field to create computer images of the brain and spinal cord.
• X-ray. Electromagnetic energy is used to create images of the head and neck. This can show bone abnormalities in the skull and spine.

If diagnostic tests show that a Chiari malformation is present, a neurosurgeon will discuss with you the best treatment options for your child.