Newswise — The symptoms can mimic so many other conditions that patients are often told that their chronic headaches and muscle weakness are psychosomatic, or that the symptoms are "all in their head." Chiari malformation is indeed in the head, but it is a physical condition, most often congenital in nature. According to the American Association of Neurological Surgeons (AANS), the prevalence in the general population is estimated at slightly less than one in 1000.
Some patients with Chiari experience symptoms similar to those of fibromyalgia and chronic fatigue syndrome, which are also challenging to diagnose and treat. "Chiari that goes undiagnosed for a lengthy time can lead to real psychological problems in some patients, making the condition even more problematic to treat," said Ghassan Bejjani, MD, AANS spokesperson and an expert on Chiari.
A German pathologist named Hans Chiari was the first to describe the disorder in the early 1890s. He categorized these in order of severity: types I, II, III, and IV. The term "Arnold-Chiari" was latter applied to Chiari type II malformation. Chiari types III and IV are quite rare and usually seen in conjunction with other severe birth defects and high infancy mortality rates.
Chiari type 1 malformation occurs during fetal development and is characterized by downward displacement by more than four millimeters, of the cerebellar tonsils beneath the foramen magnum into the cervical spinal canal. This displacement may block the normal pulsations of cerebral spinal fluid (CSF) between the spinal canal and the intracranial space. Some people with type 1 have no symptoms and are not aware that they have the condition until they undergo radiological studies for other medical problems. Type 1 is diagnosed more commonly in adolescents or adults.
Chiari type II malformation is characterized by downward displacement of the medulla, fourth ventricle, and cerebellum into the cervical spinal canal, as well as elongation of the pons and fourth ventricle. This type occurs almost exclusively in patients with myelomeningocele, a congenital condition in which the spinal cord and column do not close properly during fetal development, resulting in an open spinal cord defect at birth.
Patients with Chiari often have a condition called syringomyelia or hydromyelia. This condition arises when CSF forms a cavity or cyst within the spinal cord. As the fluid cavity expands, it can displace or injure the nerve fibers inside the spinal cord. A wide variety of symptoms can occur, depending on the size and location of the syrinx. Loss of sensation in an area served by several nerve roots is one typical symptom, as is the development of scoliosis.
"In treating patients with Chiari, I take into consideration the severity of the symptoms and how they are affecting their quality of life," stated Dr. Bejjani. "In many cases, symptoms can be addressed individually through nonsurgical treatments. Some patients can cope with the symptoms without any major problems, while others are severely impacted by the condition." Symptoms vary greatly depending on the type of Chiari and the patient's own unique circumstances, but may include:
"¢Severe head and neck pain"¢An occipital headache felt at the base of the skull that is made worse by coughing, sneezing, or straining"¢Loss of pain and temperature sensation of the upper torso and arms (as a result of a syrinx)"¢Loss of muscle strength in the hands and arms (as a result of a syrinx)"¢Drop attacks " collapsing to the ground due to muscle weakness"¢Spasticity"¢Dizziness"¢Balance problems"¢Double or blurred vision"¢Hypersensitivity to bright lights
Surgical treatment of Chiari depends on the type of malformation. The goal of surgery is to relieve or stop the progression of the syrinx and/or symptoms by decompressing nerve tissue and restoring normal CSF flow around and behind the cerebellum. Decompression provides more space for the brain stem, spinal cord, and descended cerebellar components.
Type I may be treated surgically with only local decompression of the overlying bones, decompression of the bones and release of the dura (a thick membrane covering the brain and spinal cord), or decompression of the bone and dura and some degree of cerebellar tissue resection. Type II is treated similarly, but is usually restricted to decompressing the tissues in the spinal canal and leaving the back of the skull alone.
The benefits of surgery should always be weighed carefully against its risks. Although some patients experience a reduction in their symptoms, there is no guarantee that surgery will help every individual. Nerve damage that has already occurred usually cannot be reversed. Some surgical patients need repeat surgeries, while others may not achieve symptom relief.
For more information on Chiari and other neurological conditions, please visit: http://www.neurosurgerytoday.org/what/patient_e/chiari1.asp.
Founded in 1931 as the Harvey Cushing Society, the American Association of Neurological Surgeons (AANS) is a scientific and educational association with more than 6,800 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public. All active members of the AANS are certified by the American Board of Neurological Surgery, the Royal College of Physicians and Surgeons (Neurosurgery) of Canada or the Mexican Council of Neurological Surgery, AC. Neurological surgery is the medical specialty concerned with the prevention, diagnosis, treatment and rehabilitation of disorders that affect the entire nervous system, including the spinal column, spinal cord, brain, and peripheral nerves.
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