Spina Bifida Family Support
"Families Helping Families"
Symptomatic Chiari Malformation
By W. Jerry Oakes M.D., Children's' Hospital of Alabama
Persons with myelomeningocele have abnormalities that are not limited to their spinal cord. These include the development of hydrocephalus (in up to 95% of patients) and the development of symptoms related to the area where the brain and spine join (Chiari malformation).
Over a hundred years ago, Professor Chiari, an Australian pathologist studied a group of patients who had a portion of the brain displaced into the neck. He graded these malformations in severity from Type I (the mildest form) where the lowest part of the cerebellum, called the cerebellar tonsils descend a short distance into the cervical spine, to Type III (the most severe form) where large portions of important brain areas are displaced into a sac at the top of the neck.
A vast majority of spina bifida patients have the intermediate form (Chiari Type II or Arnold-Chiari malformation), in which the cerebellar vermis and some portion of the brain stem descend into the cervical spine. Many changes of the brain are associated with this abnormality.
Although some degree of this malformation is present in the vast majority of persons with spina bifida, it appears to be symptomatic in about one of three individuals. This 33% may be a falsely low figure in that, as we follow patients for longer periods of time, adolescents and young adults appear to have some propensity to develop clinical progression attributable to this lesion. The development of symptoms related to the Chiari malformation is, in part, related to the severity of the malformation.
For example, when brain tissue is below the level of the fourth cervical vertebrae (C4), the likelihood of serious symptoms occurring from this abnormality is high. On the other hand, minor degrees of descent of the brain well above the level of C3, are less likely to have clearly recognized progressive symptoms.
Symptoms, when they occur, tend to come from one of three areas of the central nervous system: cerebellum, lower brain stem and spinal cord. The symptom complex is quite different with each of these and appears to be predictable to some degree depending on the patient's age at presentation. Newborns and young infants with symptoms tend to present difficulty swallowing that leads to poor feeding, weak or poor cry, inspiratory stridor (noise on breathing in) frequently exacerbated by crying, arching of the head and possibly facial weakness, among others. When severe, the symptoms may result in insufficient breathing to maintain life. The symptomatic Chiari malformation is currently the leading cause of death in the spina bifida population, particularly early in life.
The child or adolescent may develop stiffness or spasticity of the arms or hands. This stiffness may be so severe that the upper extremities will not work smoothly. If these symptoms are progressive, they may make the upper extremities useless to the patient. Associated with the stiffness may be loss of feeling or sensation in the hands or arms. This loss may not be to all types of sensation, but may be restricted to only certain types such as the loss of pain or of temperature.
The third area that can be affected is the cerebellum. This portion of the brain, located in the back of the head, controls balance and coordination. These symptoms are the least likely to occur and may be the most difficult to pinpoint especially in the younger child.
With the advent of magnetic resonance imaging (MRI), the evaluation of structural abnormalities of the cervical spine has become greatly simplified. Although other methods are available, MRI provides extremely high-resolution images of the area of concern with little to no risk to the patient. Not only can the position of the brain be obtained by even cysts or other problems with the spinal cord can be assessed. The MRI scan can also be used to evaluate flow of cerebrospinal fluid (CSF) around the back part of the brain. Additional examinations, which test the integrity of the functional aspects of the brain stem and spine, are sometimes helpful. These include a CO2 breathing test that reflects the function of the brain's breathing center, somatosensory evoked response (timing of electrical signals that connect the arms and legs with the brain), brain stem evoked response (ability of the brain to process sounds) and others.
Of primary importance in patients suspected of being symptomatic from their Chiari malformation is to ensure normal intracranial pressure prior to any consideration of intervention for the Chiari malformation. This means that the patient should have her/his shunt evaluated first. The "shunt first" approach can not be over emphasized. If there is any question concerning shunt function the system should be surgically inspected. Once it is determined that the intracranial pressure is normal and that the shunt is working properly, the next question to be answered is whether the patient's symptoms are life threatening and/or progressive. Most patients with radiographic evidence of a Type II Chiari malformation do not need surgery and appear not to be progressive. If serious symptoms are present, consideration is given to surgical intervention. The purpose of the operation is to unroof the cervical spine over the abnormally low brain and to reestablish normal movement of the CSF.
The operation is relatively safe in experienced hands but should only be performed by a surgeon especially trained and experienced in operations on children's brain malformations. The technical excellence necessary to perform this operation is high and there is not substitute for significant experience. The alternative strategy of further conservative care of patients with symptomatic Chiari malformation demands special comment. It is currently believed that the majority of spina bifida patients do not demonstrate rapid clinical progression. Generally, the more the patient's progression is felt to be secondary to their Chiari malformation, the more universal is the acceptance of operative intervention. Serial examinations of the individual are essential in the evaluation of this problem and again fix the shunt first.
This information does not constitute medical advice for any individual. As specific cases may vary from the general information presented here, Spina Bifida Family Support advises readers to consult a qualified medical or other professional on an individual basis.
Back to Main