Arnold Chiari Malformation is diagnosed through Magnetic resonance imaging. Arnold Chiari Malformation, also referred to as CM, is believed to have a genetic predisposition as well as other causal agents such as brain or head trauma. CM is a structural defect in the cerebellum. The cerebellum should sit above the forum magnum (opening in the base of the skull) in the skull; however, with CM the cerebellum sits below the forum magnum. With CM, the cerebellum and the brainstem are pushed downward into the upper spinal canal, which can cause partial or complete blockage of the cerebral spinal fluid flow. Many individuals never know that they have this particular brain abnormality, as it can remain asymptomatic; however, numerous individuals do present with symptoms.
CM can cause a multitude of symptoms with one of the most prominent being headaches. According to the National Institute for Health, other symptoms that can present with CM are neck pain, balance problems, muscle weakness, numbness or other abnormal feelings in the arms or legs, dizziness, vision problems, difficulty swallowing, ringing or buzzing in the ears, hearing loss, vomiting, insomnia, depression, or headache made worse by coughing or straining. Hand coordination and fine motor skills may be affected. These symptoms can change as the flow of spinal fluid changes due to the position or re-positioning of the CM. CM can occur with or possibly result in other disorders such as syringomyelia. Syringomyelia presents as a syrinx, or a tubular cyst filled with spinal fluid and these are found within the spinal cords central canal. These cysts, according to the National Institute for Health, grow and in doing so they destroy the center of the spinal cord, resulting in pain, weakness, and stiffness in the back, shoulders, arms, or legs.
CMs are found in various types and degrees although CM I is the most common type presenting. Severity of a CM is measured by the size of the CM in millimeters and the resultant symptoms. There has been controversy surrounding the size of the CM and presenting symptoms. Another form of the disorder, under debate by some scientists, is Type 0, in which there is no protrusion of the cerebellum through the foramen magnum but headache and other symptoms of CM are present. So we must wonder—does size matter when it references a CM and the presentation of symptoms?
At this time, there are four truly recognized types of Chiari Malformation: Type I, Type II, Type III and Type IV. Type II is uncommon and types III and IV are extremely rare and will not be discussed in this particular article, leaving type I as the most commonly diagnosed. Chiari Type I is defined as an abnormal protrusion of the tonsils of the cerebellum through the foramen magnum (opening at the base of the skull) down into the cervical spinal canal. In most instances, Chiari is believed to be caused by incorrect growth of the skull resultant of insufficient room for the structures (cerebellum) which belong there.
Bermans J. Iskandar was the first to use the term Chiari 0 malformation. Iskander used this term at a meeting of the Pediatric Neurosurgery Section of the American Association of Neurological Surgeons (AANS) in Louisiana, New Orleans. Iskander actually used this term as early as 1997. Iskandar and his team defined Chiari 0 malformation as an obstruction caused by a small and malformed posterior fossa (small space in the skull, found near the brain stem and cerebellum) without evidence of cerebral tonsil herniation.
Many still believe that the degree of herniation of the cerebellum’s tonsils corresponds to the severity of symptoms; however, many studies seem to be proving this belief as false. The ASPA provides a handbook for Chiari patients that describe the different types of Chiari. Within this handbook, Chiari 0 is considered relevant and makes allowance for those with little or no visible herniation of the cerebellum’s tonsils to have hope for intervention when they approach their neurologists or other specialists with their Chiari type I symptoms.
With so many studies supporting a Chiari type 0 and the fact that it responds as well to surgery as type I by relieving patients of their Chiari type I symptoms should justify its existence. Individuals who present with a Chiari type 0 deserve the same consideration and treatment as an individual presenting with any of the other types. Unfortunately, there still seems to be resistance to the effects that Chiari type 0 can have. The Chiari I symptoms are highly disputed by many neurologists and neurosurgeons when a patient presents with Chiari 0. Ultimately, this will certainly change as further studies are conducted and as the empirical evidence continues to point in the right direction.
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