Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. Often, syringomyelia is used as a generic term before an etiology is determined. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in loss of feeling, paralysis, weakness, and stiffness in the back, shoulders, and extremities. Syringomyelia may also cause a loss of the ability to feel extremes of hot or cold, especially in the hands. It may also lead to a cape-like bilateral loss of pain and temperature sensation along the upper chest and arms. The combination of symptoms varies from one patient to another depending on the location of the syrinx within the spinal cord, as well as its extent. Syringomyelia has a prevalence estimated at 8.4 cases per 100,000 people, with symptoms usually beginning in young adulthood. Signs of the disorder tend to develop slowly, although sudden onset may occur with coughing, straining, or myelopathy.
Signs and symptoms Syringomyelia causes a wide variety of neuropathic symptoms, due to damage to the spinal cord. Patients may experience severe chronic pain, abnormal sensations and loss of sensation, particularly in the hands. Some patients experience paralysis or paresis, temporarily or permanently. A syrinx may also cause disruptions in the parasympathetic and sympathetic nervous systems, leading to Horner syndrome, abnormal body temperature or sweating, bowel control issues, or other problems. If the syrinx is higher up in the spinal cord or affecting the brainstem, as in syringobulbia, vocal cord paralysis, ipsilateral tongue wasting, trigeminal nerve sensory loss, and other signs may be present. Rarely, bladder stones can occur at the onset of weakness in the lower extremities. Classically, syringomyelia spares the dorsal column/medial lemniscus of the spinal cord, leaving pressure, vibration, touch and proprioception intact in the upper extremities. Neuropathic arthropathy, also known as a Charcot joint, can occur, particularly in the shoulders, in patients with syringomyelia. The loss of sensory fibers to the joint is theorized to lead to degeneration of the joint over time.
Cause Generally, there are two forms of syringomyelia: congenital and acquired. Syringomyelia is generally a chronic disorder that occurs over time, resulting in muscular atrophy. Acquired Syringomyelia can be caused by a serious physical trauma to the body such as in a road traffic accident. Syringomyelia can also be classified into communicating and noncommunicating forms. Communicating typically occurs due to lesions on the foramen magnum and noncommunicating occurring due to other spinal cord diseases.
Congenital The first major form relates to an abnormality of the brain called an Arnold–Chiari malformation or Chiari malformation. This is the most common cause of syringomyelia, where the anatomic abnormality, which may be due to a small posterior fossa, 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. Here, symptoms usually begin between the ages of 25 and 40 and may worsen with straining, called a valsalva maneuver, or any activity that causes cerebrospinal fluid 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 cerebrospinal fluid accumulates in the skull, or a condition called arachnoiditis, in which a covering of the spinal cord—the arachnoid membrane—is inflamed. Some cases of syringomyelia are familial, although this is rare.
Acquired 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 (often referred to using the abbreviation of PTS) is pain, which may spread upward from the site of injury. Symptoms, such as pain, numbness, weakness, and disruption in temperature sensation, may be limited to one side of the body. Syringomyelia can also adversely affect sweating, sexual function, and, later, bladder and bowel control. A typical cause of PTS would be a car accident or similar trauma involving a whiplash injury. What can make PTS difficult to diagnose is the fact that symptoms can often first appear long after the actual cause of the syrinx occurred (e.g., a car accident occurring and then the patient first experiencing PTS symptoms such as pain, loss of sensation, and reduced ability on the skin to feel varying degrees of hot and cold a number of months after the car accident).
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