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Chiari Malformations: Causes, Symptoms and Treatment

New York (Aug 20, 2010)

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Children, as well as adults, will experience headaches at various times in their lives. However, pediatricians should be aware that what they might ordinarily dismiss as ordinary headaches could, in some cases, also be symptomatic of Chiari malformation.

"Chiari malformation is a relatively rare abnormality of the cerebellum," says Mark M. Souweidane, MD, Chief, Pediatric Neurosurgery, Phyllis and David Komansky Center for Children's Health, NewYork-Presbyterian/Weill Cornell. "When the indented bony space at the lower rear of the skull is smaller than normal, the cerebellum and brainstem can be pushed downward. The resulting high pressure on the cerebellum can block the flow of cerebrospinal fluid and affect the function of the cerebellum, the brain stem, and spinal cord causing a range of symptoms, including headache, dizziness, muscle weakness, numbness, and problems with balance and coordination."

According to Dr. Souweidane, the headache is generally short lived and not associated with typical migraine symptoms such as visual problems, nausea, and vomiting. Another common manifestation of Chiari that is seen in the pediatric population is an atypical scoliosis. Many patients with symptoms from a Chiari malformation will also have syringomyelia, a condition in which spinal fluid accumulates in the spinal cord. Other conditions sometimes associated with Chiari malformation include scoliosis, hydrocephalus and certain craniofacial disorders.

Types of Chiari Malformation (CM)

There are three primary types of CM:

Type I In Type I, the most common form of Chiari malformation, signs and symptoms do not appear until late childhood or early adulthood. Headaches often severe are the classic symptoms of Chiari I.

Type II Also called Arnold-Chiari malformation, Type II is usually accompanied by a myelomeningocele a form of spina bifida that occurs when the spinal canal and backbone do not close before birth, causing the spinal cord to protrude through an opening in the back and result in partial or complete paralysis below the spinal opening.

Type III This is the most serious form of CM and causes severe neurological defects. A portion of the lower back part of the cerebellum or the brainstem extends through an abnormal opening in the back of the skull.

"Chiari Type I is a congenital disease that generally affects adolescents and young adults," says Dr. Souweidane. "It has a number of different manifestations or symptoms ranging from the asymptomatic patient incidentally diagnosed to the patient who had scoliosis or a neurologic disorder. Most commonly a patient will present with complaints of headaches that are fairly characteristic and can be quite unique. They are typically suboccipital headaches at the skull base, neck, and the shoulder and usually are associated with exertion, such as coughing or sneezing. Another common manifestation is a subjective feeling of pins and needles in the fingers.

"Less typically, infants can also manifest the disease," continues Dr. Souweidane. "When the disease presents in infancy, it can masquerade as gastroesophageal reflux, sleep apnea, failure to thrive, and less specific complaints. In these cases, the child is shuttled from specialist to specialist looking for a diagnosis. Sometimes the symptoms can be cardiac or neurologic. Syncope or fainting episodes can be misinterpreted as epilepsy."

When the cerebellum is pushed into the upper spinal canal, it can interfere with the normal flow of cerebrospinal fluid that protects the brain and spinal cord and can lead to the blockage of signals transmitted from the brain to the body, or to a buildup of spinal fluid in the brain or spinal cord. Alternatively, the pressure from the cerebellum upon the spinal cord or lower brainstem can cause neurological signs or symptoms.

"The fluid can actually accumulate within the spinal cord into very large cysts commonly called a syrinx, and can obviously have tremendous impact on motor function and sensory findings," says Jeffrey P. Greenfield, MD, PhD, Pediatric Neurosurgeon, Phyllis and David Komansky Center for Children's Health. "The art of what a pediatric neurosurgeon must do when evaluating a patient with a Chiari is to make sure that children they are seeing with radiographic Chiari actually have symptoms that may be referred from compression in this area of the brain."

Confirming a Diagnosis of Chiari I Malformation

The most definitive test used in diagnosing a Chiari malformation is magnetic resonance imaging (MRI) of the brain to detect brain stem and spinal cord compression. However, Chiari I often goes misdiagnosed, through no fault of the pediatrician, because, says Dr. Greenfield, "Pediatricians can't order an MRI for every child who gets a headache. Often parents have a lot of guilt associated with how long it takes to make the diagnosis. It comes down to understanding the specific nuances and how a Chiari headache differs from other types of headaches and when the neurologic symptoms are not routine enough to dismiss. It's difficult to try to tease out when a headache is just a headache or something more serious."

Dr. Souweidane notes that the prevalence of MRI scans being performed today for minor trauma and other conditions has elevated the number of patients that are being diagnosed with Chiari malformations. "A lot of people with a Chiari malformation would have gone their whole lives never knowing they had it," he says. "Then suddenly a parent whose child had a scan because they bumped their head now has this diagnosis. They then come to see a neurosurgeon for management of Chiari."

"Many times," says Dr. Souweidane, "we are evaluating patients not necessarily because they have symptoms of Chiari but because there is some question on findings. For example, the radiologist may say that somebody has a Chiari malformation based on the shape of the cerebellum, the descent of the cerebellum, or when it actually extends through the base of the skull. It is important to find a specialist who sees a lot of Chiari patients and understands whether or not it's something to be treated or can be left alone. When you see a patient with Chiari I, you need to be very prudent that hydrocephalus is not present as well because the treatment approach is entirely different."

Treatment for Chiari I Malformation

Though many people may have subtle Chiari malformations that are evident on an MRI, not all are severe enough to warrant treatment. However, surgery is recommended when it becomes necessary to relieve the pressure on the brain stem, cerebellum, and spinal cord and to re-establish circulation of the spinal fluid. "The treatment of Chiari is based on the decompression of the bone that is causing the asymmetric narrowing of the cervical medullary junction at the base of the brain and the top of the spinal cord," says Dr. Greenfield. "The procedure, which is effective in 90 percent of patients, involves dissecting the muscle at the base of the skull, opening a small window of bone and then often removing some of the bone on top of the spinal cord as well."

"The second part of the operation can involve opening the dura the sack that encloses the brain to release pressure even further and then put a patch on that," says Dr. Souweidane. "Either way, the bone is not put back on, the muscle is closed, the skin is closed, and that essentially achieves a mechanical decompression of the area."

While there is some difference of opinion among neurosurgeons about whether to do the dura opening procedure, Dr. Souweidane believes the decision depends on the patient's symptoms and age. "Some patients probably benefit from dural-sparing procedures, but I believe in doing both the boney decompression and the durotomy because without it, the recurrence rate for a second operation is somewhat higher."

According to Dr. Souweidane, without surgery, patients who are participating in high contact sports have a higher than average risk for sustaining a head injury or other severe injury. "The surgery allows peace of mind for the patient and the family for the patient to return to sports," he adds.

Contributing faculty for this article:

Mark M. Souweidane, MD, Chief, Pediatric Neurosurgery, Phyllis and David Komansky Center for Children's Health, NewYork-Presbyterian/Weill Cornell, and Professor of Neurological Surgery, Weill Cornell Medical College

Jeffrey P. Greenfield, MD, PhD, Pediatric Neurosurgeon, Pediatric Neurosurgery, Phyllis and David Komansky Center for Children's Health, NewYork-Presbyterian/Weill Cornell, and Assistant Professor of Neurological Surgery in Pediatrics, Weill Cornell Medical College

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