Weill Medical College of Cornell University

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Chiari Malformation

• Brain Abscess
• Brain Tumors in Children
• Brainstem Gliomas
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• Chiari Malformation
• Congenital Malformations of the Head and Spine
• Craniofacial Anomalies, Overview
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• Spina Bifida and Spinal Dysraphism
• Tethered Spinal Cord
• Vascular Malformations and Hemangiomas

What is a Chiari malformation?

A Chiari malformation is a congenital (present at birth) and rarely an acquired (develops over time) defect in the area of the back of the head that affects the cerebellum, a portion of the brain normally responsible for coordination of movement. Chiari malformation type I is by far the most common although there are four types.

type I - This malformation consists of "crowding" at the base of the skull due to herniation of some brain tissue (cerebellar tonsils) into a large opening called the foramen magnum. This site is where the spinal cord enters the skull and attaches to the brain.

type II - This malformation is always seen in children who are born with an open neural tube defect (spina bifida aperta or myelomeningocele), a neurological condition that results in a portion of the spinal cord being exposed at the skin surface of the back. Many of these patients also have hydrocephalus.

type III - This malformation consists of an obvious defect at the back of the head that is caused by some intracranial contents forming outside the skull. These defects are usually covered by normal skin.

type IV - This defect is characterized by some degree of developmental failure of the back of the brain called the cerebellum. This type of Chiari malformation does not have any herniation of tissue.

What causes Chiari Malformation Type I (CM-I)?

Although the exact cause of CM-I malformation is unknown, it is thought to arise from abnormal brain formation during fetal development. There is some association with genetic predisposition meaning that the defect can be seen in family members . Rarely, CM-I can be associated with other conditions that affect bone growth and development including craniosynostosis and achondroplasia.

What are the symptoms of a Chiari malformation?

The majority of persons with CM-I do not have symptoms. Most patients become symptomatic in their late childhood and early adult life (10–20 years of age). The most frequent complaint is headache. This type of headache is usually characterized by tightness or discomfort in the back of the head and neck. This discomfort is commonly made worse with activities including exercise, coughing or sneezing, and even laughing. Another very common complaint is temporary tingling or numbness in the hands and fingers. Many children are also diagnosed with spinal deformity, a condition called scoliosis. Less frequently, patients may also experience transient fainting episodes, commonly referred to as syncope. In very young children (less than 3 years of age) the child is commonly misdiagnosed with feeding difficulties, delayed speech development, and poor weight gain.

• rapid, back and forth, eye movement
• developmental delays
• poor feeding and swallowing
• stiffness or pain in the neck or back of the head area
• weak cry
• breathing problems
• headaches
• decreased strength in the arms

Because the symptoms of Chiari malformation type I may resemble other conditions or medical problems, always consult your physician for a diagnosis.

How is a CM-I diagnosed?

MR scanning defines CM-I in most patients. While CT scans of the brain will show evidence of CM-I the use of MRI better defines the details of the malformation and other brain features. In addition to an MRI scan of the brain a total spinal MRI is recommended to assess 1) the presence of syringomyelia, fluid accumulation within the spinal cord, and 2) the presence of a tethered spinal cord. Special MRI studies that are designed to monitor fluid around the CM-I are possible and may help in the decision making process regarding treatment.

Treatment for a Chiari malformation

A major decision regarding CM-I is whether the patient has symptoms that are arising from the malformation and hence whether they may benefit from surgery. This decision is dependent upon a thorough clinical history and a detailed neurological examination. In some situations assessments by other specialists including otolaryngologists (ENT), cardiologist, and gastroenterologists can be beneficial. When a patient is thought to have an asymptomatic CM-I malformation, then observation with yearly MRI scans of the brain and cervical spine are usually recommended.

If the CM-I is believed to be responsible for the patient's symptoms or the clinical examination is abnormal, then treatment is recommended. Treatment is surgical and the results are usually excellent. The principle behind treatment is to increase the size of the major opening in the skull base, the foramen magnum and the size of the upper cervical spine canal. This procedure is referred to as a decompressive suboccipital craniotomy with cervical laminectomy. Depending on the particular case treatment options include this decompression with or without opening of the thick tissue covering this area, the dura. In the minimally invasive endoscopic approach, the surgery can be as short as 1–2 hours. The good news with treatment is that nearly all patients (greater than 90%) enjoy partial or complete improvement in their symptoms with negligible risk. Depending on the surgical technique, patients are usually in the hospital for 1–5 days.

In rare circumstances, patients with CM-I may have hydrocephalus, a condition in which normal fluid in the brain is increased. In these situations, treated can be simplified through a minimally invasive surgery that results in the drainage of this fluid. This procedure, endoscopic third ventriculostomy (ETV), avoids any bone removal and usually involves only an overnight hospitalization.

Patients will usually undergo a MRI during the months after surgery. If the patient does show improvement and the MRI shows an adequate decompression, then patients are usually seen on an annual basis for several years without further studies. After treatment patients are expected to return to their normal level of activity including exercise and organized athletics! Even with treatment however avoidance of full-contact helmeted sports at a high-school level or beyond are discouraged.

Frequently Asked Questions