Figure 7. In Chiari type 0, the tonsils do not herniate out of the skull, but CSF flow is blocked causing a syrinx. Syringomyelia is a condition in which CSF collects and forms a cyst, called a syrinx, within the spinal cord.
Figure 8. MRI of a person with a large arachnoid cyst under the cerebellum. Syrinx cavities can be seen in the neck and thoracic spine (arrows).
Syringomyelia (pronounced sir-RING-o-my-elia) is the development of a fluid-filled cyst (syrinx) within the spinal cord. When cerebrospinal fluid (CSF) flow is obstructed and collects within the spinal canal, it can eventually form a syrinx. The syrinx expands and elongates over time, then damaging the center of the spinal cord. The compressed nerve fibers inside the cord cause a wide variety of symptoms. Problems affect the arms or legs, or affect feeling, strength, or balance.
• Loss of sensitivity, especially to hot and cold
• Sensory loss in a "cape" distribution (over the tops of the shoulders)
• Numbness and tingling in hands and feet
• Muscle weakness and spasticity
• Headaches (due to Chiari malformation)
• Pain in neck, arms and back
• Loss of bowel and bladder control
• Scoliosis (curvature of the spine)
Cerebrospinal fluid normally flows in a pulsatile manner throughout the subarachnoid space surrounding the spinal cord and brain. Blockage of flow or changes in pressure can cause CSF to collect inside the central canal — a narrow channel down the middle of the spinal cord.
About 65% of patients with Chiari I develop syringomyelia, which can cause irreversible damage to the spinal cord. In Chiari type 0, patients have no herniation of the tonsils, but do have a syrinx in the spinal cord that causes symptoms (Fig. 7). Chiari 0 is sometimes called "borderline" Chiari. This variant supports the clinical finding that symptoms are caused by CSF flow obstruction and do not directly related to the size of tonsillar herniation.
Syringomyelia can also form as a complication of spine injury, meningitis, spinal cord tumor, arachnoiditis, arachnoid cysts (Fig. 8), or a tethered spinal cord. Symptoms may appear years after the initial injury.
If syringomyelia is caused by a Chiari malformation, surgery will likely be recommended. A neurosurgeon will remove bone at the back of the skull to enlarge the opening. The dura overlying the tonsils is opened and a patch is sewn to expand the space, similar to letting out the waistband on a pair of pants. In most cases, this surgery can restore the normal flow of CSF and may allow the syrinx to drain on its own.
If syringomyelia is caused by a lesion, treatment may involve removing a tumor or scar tissue. In cases of a tethered spinal cord, surgery may be performed to release the attachment on the cord at the filum terminale.
Another treatment option is to drain the syrinx. A neurosurgeon can surgically insert a drainage system, called a shunt. The shunt includes a flexible tube with a 1-way valve that directs the fluid out of the syrinx and in the desired direction. One end of the tubing is placed in the syrinx. The other end is placed outside the spinal cord. The shunt remains inside the spine after surgery. However, shunts pose risks and often become clogged or dislodge. Repeated surgeries may be necessary.
reviewed by: Andrew Ringer, MD, John M. Tew, MD, and Nancy McMahon, RN
University of Cincinnati Department of Neurosurgery