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. When a syrinx widens enough to affect nerve fibers that carry information from the brain to the extremities, this damage results in pain, weakness, and stiffness in the back, shoulders, arms, or legs. Other symptoms may include headaches and a loss of the ability to feel extremes of hot or cold, especially in the hands. Each patient experiences a different combination of symptoms depending on where in the spinal cord the syrinx forms and how far it expands.
Other, more common disorders share the early symptoms of syringomyelia. In the past, this has made diagnosis difficult. But the widespread availability of an outpatient imaging procedure called magnetic resonance imaging (MRI) has significantly increased the number of syringomyelia cases diagnosed in the beginning stages of the disorder.
Signs of the disorder tend to develop slowly, although sudden onset may occur with coughing or straining. If not treated surgically, syringomyelia often leads to progressive weakness in the arms and legs, loss of hand sensation, loss of bladder and other functions, and chronic, severe pain.
A watery, protective substance known as cerebrospinal fluid (CSF) normally flows around the spinal cord and brain, transporting nutrients and waste products. It also serves to cushion the brain. In early development, CSF also fills a small canal 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 it into the central canal, and ultimately into the spinal cord itself. For reasons that are only now becoming clear, this redirected CSF fills the expanding central canal and results in syrinx formation. Pressure differences along the spine cause the fluid to move within the cyst. Physicians believe that it is this continual movement of fluid that builds pressure around and inside the spinal cord, and results in cyst growth and further damage to the spinal cord tissue.
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 the physician 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 patients, however, may have long periods of stability. Some patients with this form of the disorder also have hydrocephalus, in which CSF accumulates in the skull, 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.
In addition, one form of the disorder involves 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. Some cases of syringomyelia are familial, although this is rare.
Physicians now use magnetic resonance imaging (MRI) to diagnose syringomyelia. The MR imager takes pictures of body structures, such as the brain and spinal cord, in vivid detail. This test will show the syrinx in the spine as well as other conditions, such as the presence of a tumor. MRI is safe, painless, and informative and has greatly improved the diagnosis of syringomyelia. Images taken in rapid succession can be used for “dynamic imaging” (in “cine mode”) to observe the fluid flowing around the spinal cord and within the syrinx.
The physician may order additional tests to help confirm the diagnosis. One of these is called electromyography (EMG), which measures muscle weakness. The doctor may also wish to test CSF pressure levels and to analyze the CSF by performing a lumbar puncture. In addition, computed tomography (CT) scans of a patient's head may reveal the presence of tumors and other abnormalities such as hydrocephalus.
Like MRI and CT scans, another test, called a myelogram, takes x-ray-like pictures and requires a contrast medium or dye to do so. Since the introduction of MRI this test is rarely necessary to diagnose syringomyelia.
Surgery is usually recommended for syringomyelia patients. The main goal of surgery is to provide more space for the cerebellum (Chiari malformation) at the base of the skull and upper neck, without entering the brain or spinal cord. This results in flattening or disappearance of the primary cavity. If a tumor is causing syringomyelia, removal of the tumor is the treatment of choice and almost always eliminates the syrinx.
Surgery results in stabilization or modest improvement in symptoms for most patients. Delay in treatment may result in irreversible spinal cord injury. Recurrence of syringomyelia after surgery may make additional operations necessary; these may not be completely successful over the long term.
In some patients it may be necessary to drain the syrinx, which can be accomplished using a catheter, drainage tubes, and valves. This system is also known as a shunt. Shunts are used in both the communicating and noncommunicating forms of the disorder. First, the surgeon must locate the syrinx. Then, the shunt is placed into it with the other end draining the syrinx fluid into a cavity, usually the abdomen. This type of shunt is called a syringoperitoneal shunt. A shunt of CSF from the brain to the abdomen is called a ventriculoperitoneal shunt and is used in cases involving hydrocephalus. By draining syrinx fluid or CSF, a shunt can arrest the progression of symptoms and relieve pain, headache, and tightness. Without correction, symptoms generally continue.
The decision to use a shunt requires extensive discussion between doctor and patient, as this procedure carries with it the risk of injury to the spinal cord, infection, blockage, or hemorrhage and may not necessarily work for all patients.
In the case of trauma-related syringomyelia, the surgeon operates at the level of the initial injury. The most common approach was to collapse the cyst in surgery and insert a tube or shunt to prevent its re-expansion. Because shunts routinely become clogged and require multiple operations, many surgeons now consider this option only as a last resort. Instead, surgeons now expand the space around the spinal cord by realigning the vertebrae or discs that are narrowing the spinal column. They then add a patch to expand the “dura,” the membrane that surrounds the spinal cord and contains the CSF (a procedure called “expansive duraplasty”). It is also considered important to remove scar tissue attached to the membranes that “tether” the cord in place and prevent the free flow of CSF around it.
Drugs have no curative value as a treatment for syringomyelia. Radiation is used rarely and is of little benefit except in the presence of a tumor. In these cases, it can halt the extension of a cavity and may help to alleviate pain.
In the absence of symptoms, syringomyelia is usually not treated. In addition, a physician may recommend not treating the condition in patients of advanced age or in cases where there is no progression of symptoms. Whether treated or not, many patients will be told to avoid activities that involve straining.
Many spinal cord injured individuals have a cyst at the site of their original injury. These cysts do not always require treatment, although if they grow larger or begin to cause symptoms treatment may be warranted.