What is Syringomyelia and what is a Syrinx?
Syringomyelia is a condition that occurs when spinal fluid collects inside the spinal cord. The spinal cord is connected to the lower part of the brain, called the brainstem. The spinal cord is a delicate structure that rests within the spinal canal and is surrounded by a tough outer covering, called the dura. Normally, the spinal cord ends at about the first or second lumbar vertebrae in the adult. The spinal canal is surrounded and protected by the bony structure of the spinal column (or vertebrae). Cerebrospinal fluid (CSF) surrounds the spinal cord and flows from the brain, down the spinal canal and back up to the brain. Normally, there is no CSF within the spinal cord itself, instead, the CSF surrounds the spinal cord. Many nerves originate from the spinal cord, and are responsible for movement and sensation of the arms, legs and torso.
Syringomyelia was first described by Antione Portal in 1803. He described a patient who experienced numbness and loss of function of the lower extremities. An abnormal cavity, called a syrinx (see-rin-x), was found on autopsy examination of the spinal cord.
On the left is a side-view T1 MRI showing a large syrinx (dark oval cavity) in the spinal cord running from the cervical 2 to cervical 4. On the right is another person's side-view MRI done in a T2 sequence that show the spinal fluid as white. You can see the severe crowding from herniation of the cerebellar tonsils at the base of the skull. There are three syrinx cavities developing in the spinal cord. If left untreated, these three cavities would likely become one long syrinx.
The fluid cavity can be thought of something like a blister, and causes pressure from the inside of the spinal cord. The pressure disrupts the normal function of the nerves and nerve bundles (tracts) that travel in that area of the spinal cord.
What causes Syringomyelia?
The most common cause of syringomyelia is the Chiari malformation. However, not everyone who has Chiari malformation will develop syringomyelia. The exact cause of syringomyelia is not known. In general it is believed that the blockage of normal spinal fluid flow at the foramen magnum caused by the Chiari malformation results in fluid collecting inside of the spinal cord.
The syrinx can enlarge over time and stretch the delicate nerves that run in the spinal cord. There is no specific, predictable pattern of enlargement of the syrinx cavity. Some syringes remain unchanged for many years, while others may enlarge over a shorter period of time.
Other causes of syringomyelia include an injury to the spinal cord, spinal tumors, or other lesions inside the spinal canal. Arachnoiditis (inflammation of the thin membrane just inside the dura membrane) can also create an abnormal spinal cavity, and cause a syrinx to develop. In some cases, the cause of the syrinx is unknown (called idiopathic).
The test of choice for diagnosis of a syrinx is an MRI of the spine. The most common area for a syrinx to develop in persons with CM-I is in the cervical spine (neck). The second most common area is the thoracic spine. As the syrinx grows in size, it may cause scoliosis (abnormal curve of the spine), which is best evaluated by special x-rays of the spine.
What symptoms develop from Syringomyelia?
Many of the symptoms of syringomyelia may be vague and variable at first, however symptoms can be progressive over a long period of time. Some people experience symptoms that occur suddenly, and some report symptoms starting after a minor injury.
Pain - Pain is one of the most common symptoms persons with syrinx may experience. People may complain of pain in the arm, hand or leg. Some people report a burning sensation around the ribs or in the neck or back. Often the pain is present for months to years before a proper diagnosis is made. Pain can also be described as dull and aching, or stabbing. Pain on one side of the body (unilateral) is more common than on both sides (bilateral).
Tingling or numbness (often called paresthesia) - Many persons report a tingling sensation in the arm, chest or back. Some persons also report tingling or numbness in the leg or foot. If left unchecked, some people will report burning or injuring themselves without realizing it due to numbness.
Weakness - Some people will report weakness in the hand, arm, or even in the leg or foot. Weakness is generally progressive over time and many people will say they have become clumsy with their fine motor movements. Over time, some persons can develop muscle wasting (atrophy). Weakness of the lower extremities may cause problems with walking (called ataxia), and some may report frequent falling.
What is the treatment for Syringomyelia?
The best treatment for syringomyelia is to remove the block to normal spinal fluid flow if there is one. In patients with syringomyelia due to the blockage caused by a Chiari I Malformation, the goal is to create more room at the foramen magnum (through a posterior fossa decompression). For many, the improved spinal fluid flow will result in the syrinx slowly decreasing in size, although it may not disappear completely. The goal is to keep the syrinx from growing and allow it to relax and decrease in size.
When syringomyelia is due to spinal injury, release of the scar bands around the spinal cord can result in a decrease in the size of the syrinx. When it is due to a spinal cord tumor, usually the best treatment is removal of the tumor, if possible. When the cause of the syrinx is not known, the treatment decisions are more difficult. Some people may respond to sectioning the band at the end of the spinal cord, the filum terminale. If the syrinx is small and the symptoms are under control, observation and follow-up MRI scans may be the best option.