Chiari, Part 5 of 6: Syringomyelia
Syringomyelia is an enlargement of the central spinal canal, sometimes to hugh dimensions. This central canal is almost imperceptible on a normal MRI. A very small syrinx is of no consequence generally. However, when very large or showing enlargement over time on several MRIs, chronic spinal cord injury is occurring and loss of function (weakness, decreased feeling, decreased dexterity, even paralysis) can result.
Syringomyelia, when associated with Chiari, generally resolves or stabilizes with adequate treatment of the Chiari. Very rarely it will not, and then another source for the syringomyelia must be sought, such as a tethered cord or the very rare tumor of the spine.
There are many causes of syringomyelia. In Chiari I, the Chiari is generally assumed to be the culprit. In Chiari II, the problem can be the Chiari itself, hydrocephalus, a tethered cord, or some combination of all of these.
In Chiari I, the syrinx, if present, is generally in the mid-cervical range C4-C6, and this should be checked for on a pre-op MRI. In Chiari II, the syrinx can involve the entire spinal cord and imaging of the entire spine is necessary. This will generally show a radiographic tethered cord, which may or may not be clinically significant. In either Chiari I or II, the syrinx can extend into the brainstem itself, called syringobulbia. This is usually associated with lower cranial nerve problems (swallowing issues, facial pain, etc). Syringobulbia is rare and indicates a very advanced condition.
Unless tumor is present, it is rare to operate on a syrinx directly. Such surgery is generally disappointing and can be dangerous.
Here is a picture of a large focal syrinx behind (dorsal to) the C6-T1 vertebral bodies. The cause of this particular syrinx is not immediately apparent from this image, as there is no significant chiari. A syrinx this size almost certainly warrants treatment of some sort. I will discuss syrinx further in future post, as it is an important subject in itself, with many discussion points.
Next time: The Tethered Cord