The term syringomyelia refers to a collection of differing conditions characterized by damage to the spinal cord that is caused by a formation of abnormal fluid-filled cavities (syrinx) within the cord. In 1827, French physician Charles-Prosper Ollivier d'Angers (1796–1845) suggested the term syringomyelia after the Greek syrinx, meaning pipe or tube, and myelos, meaning marrow. Later, the term hydromyelia was used to indicate a dilatation of the central canal, and syringomyelia referred to cystic cavities separate from the central spinal canal.
The cavities may be a result of spinal cord injury , tumors of the spinal cord, or congenital defects. An idiopathic form of syringomyelia (a form of the disorder without known cause) is also described in medical literature. The fluid-filled cavity, or syrinx, expands slowly and elongates over time, causing progressive damage to the nerve centers of the spinal cord due to the pressure exerted by the fluid. This damage results in pain , weakness, and stiffness in the back, shoulders, arms, or legs. People with syringomyelia experience different combinations of symptoms. In many cases, the disorder is related to abnormal lesions of the foramen magnum, the opening in the occipital bone that houses the lower portion of the medulla oblongata, the structure that links the brain and spinal cord. An additional cause of syringomyelia involves a Chiari malformation, a condition in which excess cerebral matter extends downward towards the medulla oblongata, crowding the outlet to the spinal canal. Some familial cases of syringomyelia have been observed, although this is rare. Types of syringomyelia include:
- syringomyelia with fourth ventricle communication
- syringomyelia due to blockage of cerebrospinal fluid (CSF) circulation (without fourth ventricular communication)
- syringomyelia due to spinal cord injury
- syringomyelia and spinal dysraphism (incomplete closure of the neural tube)
- syringomyelia due to intramedullary tumors
- idiopathic syringomyelia
Syringomyelia occurs in approximately eight of every 100,000 individuals. The onset is most commonly observed between ages 25 to 40. Rarely, syringomyelia may develop in childhood or late adulthood. Males are affected with the condition more often than females. No geographic difference in the prevalence of syringomyelia is known, and the occurrence of syringomyelia in different races is also unknown. Familial cases have been described.
Causes and symptoms
Most people with syringomyelia experience headaches , along with intermittent pain in the arms or legs, usually more severe on one side of the body. The pain may begin as dull or achy and slowly increases, or may occur suddenly, often as a result of coughing or straining. Pain in the extremities frequently becomes chronic. Additionally, numbness and tingling in the arm, chest, or back is often reported. The inability to feel the ground under the foot, or tingling in the legs and feet is also frequently experienced. Weakness of an extremity, leading to clumsiness in grasping objects or difficulty walking may also occur in individuals with syringomyelia. Eventually, functional use of the limb may be lost.
The cause of syringomyelia remains unknown. Not a single clear theory at the present can properly explain the basic mechanisms of cyst formation and enlargement. One theory proposes that syringomyelia results from pulsating CSF pressure between the fourth ventricle of the brain and the central canal of the spinal cord. Another theory suggests that syrinx development, particularly in people with Chiari
malformation, occurs after a difference in intracranial pressure and spinal pressure. A third theory contends that syrinx formation is caused by the cerebellar tonsils acting as a piston to produce large pressure waves in the spinal subarachnoid space, and this action forces fluid through the surface of the spinal cord into the central canal. Syringomyelia usually progresses slowly; the course may extend over many years. Infrequently, the condition may have a more acute course, especially when the brainstem is affected.
Examination by a neurologist may reveal loss of sensation or movement caused by compression of the spinal cord. Diagnosis is usually reached by magnetic resonance imaging (MRI) of the spine, which can confirm syringomyelia and determine the exact location and extent of damage to the spinal cord. The most common place for a syrinx to develop is in the cervical spine (neck), with the second most common in the thoracic spine (chest and rib areas). The least likely place for a syrinx is in the lumbar spine (lower back). MRI of the head can be useful to determine the presence of any additional lesions present, as well as the presence of hydrocephalus (excess CSF in the ventricles of the brain). As the syrinx grows in size, it may cause scoliosis (abnormal curvature of the spine), which is best determined by x ray of the spine.
Diagnosis and treatment of syringomyelia require specialized physicians, including neurologists, radiologists, neurosurgeons, and orthopedists, along with specialized nurses. Physical therapy is often useful to maximize muscular function and assist with gait (walking).
Treatment, usually surgery, is aimed at stopping the progression of spinal cord damage and maximizing functioning. Surgical procedures are often performed if there is an identifiable mass compressing the spinal cord. Additional surgical options to minimize the syrinx include correction of spinal deformities and various CSF-shunting procedures. Fetal spinal cord tissue implantation has recently been used in an attempt to obliterate syrinx. Surgery results in stabilization or modest improvement in symptoms for most patients. Many physicians advocate surgical treatment only for patients with progressive neurological deterioration or pain. Delay in treatment when the condition is progressive may result in irreversible spinal cord injury, and post-traumatic syringomyelia remains difficult to manage.
Medications (vasoconstrictors) are often prescribed to help reduce fluid formation around the spinal cord. Avoiding vigorous activity that increases venous pressure is often recommended. Certain exercises such as bending the trunk so the chest rests on the thighs may reduce the risk of syrinx expansion. People with progressive symptoms of syringomyelia, whether or not surgically treated, usually are monitored by their physician and have MRI scans completed every six to 12 months.
Recovery and rehabilitation
Despite reports of neurological recovery following surgery, most people achieve stabilization or only mild improvement in symptoms. Syringomyelia in children has a much lower incidence of sensory disturbance and pain than occurs with adolescents and adults, and is associated with a high incidence of scoliosis that is more favorable to surgical treatment. Additionally, all cases of syringomyelia do not progress at the same rate. Some people, usually with milder symptoms, experience stabilization in their symptoms for a period of years. A frequent complication of symptom progression is the person's ongoing need to adjust to evolving functional losses that accompany syringomyelia. These adjustments may result in loss of independence and loss of personal privacy. Rehabilitation may focus on maintaining functionality for as long as practically possible with the use of exercises and adaptive equipment, or, especially in the case of children, may focus on recovery from scoliosis caused by the syringomyelia.
As of February 2004, the National Institute of Neurological Disorders and Stroke (NINDS) was sponsoring three trials for the study of syringomyelia, including the physiology of syringomyelia, study and surgical reatment of syringomyelia, and genetic analysis of the Chiari I malformation.
The prognosis for persons with syringomyelia depends on the underlying cause of the syrinx and on the type of treatment. Untreated syringomyelia is compatible with long-term survival without progression in 35–50% of cases. In patients treated by shunting for syringomyelia due to spinal cord injury, long-lasting pain relief and improved strength are usually observed. Recent studies have revealed an unsatisfactory long-term prognosis due to high rates of syrinx recurrence in other forms of syringomyelia. Surgery (posterior fossa decompression) in syringomyelia associated with a Chiari malformation is described as a surgically safe procedure with a considerable chance of clinical improvement. In pediatric syringomyelia, surgery is effective in improving or stabilizing scoliosis.
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"Syringomyelia Fact Sheet." National Institute of Neurological Disorders and Stroke. February 10, 2004 (April 4, 2004). <http://www.ninds.nih.gov/health_and_medical/pubs/syringomyelia.htm>.
National Institute for Neurological Disorders and Stroke. P.O. Box 5801, Bethesda, MD 20824. (301) 496-5761 or (800) 352-9424. <http://www.ninds.nih.gov>.
Antonio Farina, MD, PhD