Post by DJ on Apr 27, 2015 16:57:51 GMT -8
What is syringomyelia?
Syringomyelia (sear-IN-go-my-EEL-ya) is a disorder in which a cyst forms within the spinal cord. This cyst, called a syrinx, expands and elongates over time, destroying a portion of the spinal cord from its center and expanding outward. As a syrinx widens it compresses and injures nerve fibers that carry information from the brain to the extremities. Damage to the spinal cord often leads to progressive weakness in the arms and legs, stiffness in the back, shoulders, arms, or legs, and chronic, severe pain. Other symptoms may include headaches, a loss of the ability to feel extremes of hot or cold (especially in the hands), and loss of bladder and other functions. Each individual experiences a different combination of symptoms depending on where in the spinal cord the syrinx forms and how far it extends. Signs of the disorder tend to develop slowly, although sudden onset may occur with coughing or straining.
Many disorders share the early symptoms of syringomyelia, which also can occur in association with other conditions. Estimates of the number of Americans with syringomyelia vary widely, but a conservative estimate is that about 40,000 people in the United States are affected, with symptoms usually beginning in young adulthood. Some cases of syringomyelia occur in more than one family member, although this is rare.
What causes syringomyelia?
A watery, protective substance known as cerebrospinal fluid (CSF) normally flows around the spinal cord and brain, transporting nutrients and waste products. It also acts as a cushion to protect the brain and spinal cord. In early development, CSF also fills a small canal that runs through the center of the spinal cord—the central canal—which then collapses normally over time.
A number of medical conditions can cause an obstruction in the normal flow of CSF, redirecting excess fluid into the spinal cord and central canal. This redirected CSF accumulates within the tissue of the spinal cord and forms a fluid-filled syrinx. Pressure differences along the spine cause the fluid to move within the syrinx and outside the spinal cord. Physicians believe that this continual movement of fluid in and around the spinal cord results in cyst growth and further damage to the spinal cord tissue.
What are the different forms of syringomyelia?
Generally, there are two forms of syringomyelia. In most cases, the disorder is related to an abnormality of the brain called a Chiari I malformation, named after one of the physicians who first characterized it. This anatomic abnormality causes the lower part of the cerebellum to protrude from its normal location in the back of the head into the cervical or neck portion of the spinal canal. A syrinx may then develop in the cervical region of the spinal cord. Because of the relationship that was once thought to exist between the brain and spinal cord in this type of syringomyelia, physicians sometimes refer to it as communicating syringomyelia. Symptoms usually begin between the ages of 25 and 40 and may worsen with straining or any activity that causes CSF pressure to fluctuate suddenly. Some individuals, however, may have long periods of functional stability. Some people with this form of the disorder also have hydrocephalus, in which CSF accumulates in the brain, or a condition called arachnoiditis, in which a covering of the spinal cord—the arachnoid membrane—is inflamed.
The second major form of syringomyelia occurs as a complication of trauma, meningitis, hemorrhage, a tumor, or arachnoiditis. Here, the syrinx or cyst develops in a segment of the spinal cord damaged by one of these conditions. The syrinx then starts to expand. This is sometimes referred to as noncommunicating syringomyelia. Symptoms may appear months or even years after the initial injury, starting with pain, weakness, and sensory impairment originating at the site of trauma.
The primary symptom of post-traumatic syringomyelia is pain, which may spread upward from the site of injury. Symptoms, such as pain, numbness, weakness, and disruption in temperature sensation, may occur on one or both sides of the body. Syringomyelia can also adversely affect sweating, sexual function, and, later, bladder and bowel control.
Syringomyelia may also involve a part of the brain called the brainstem. The brainstem controls many of our vital functions, such as respiration and heartbeat. When syrinxes affect the brainstem, the condition is called syringobulbia.