Conditions - Dilated Central Canal

With the advancement of MRI technology, individuals are being diagnosed with very small syrinxes that we were unable to detect in years prior. Some people will be told they have a slit-like syrinx or dilated central canal. These are generally 1-2 mm wide in diameter and are often described as a “nonexpansile” syrinx. To understand why this small cavity is present, a review of normal anatomy is helpful.

The spinal cord forms as a tube. On the inside of the tube is a small fluid cavity called the central canal. This disappears during development or during infancy. When the central canal does not completely close, a small leftover of the canal can be seen on MRI and is referred to as a “persistent central canal”. A radiology report may contain the phrase “a small syrinx versus a persistent central canal”. A repeat MRI may be recommended in order to determine a definite diagnosis. This often causes stress for the person waiting and hoping for a concrete diagnosis.

Our current understanding leads us to recommend that if the dilation of the central canal is not associated with any other known cause of a syrinx (such as the Chiari malformation, a tethered spinal cord, or tumor) it is likely to be a benign finding that will not cause any symptoms and is not likely to grow or enlarge. To make sure, a follow up MRI is usually ordered. In cases where an underlying condition known to be associated with syrinx formation is present (such as a Chiari malformation) or if repeated imaging shows a change in the dilation, then it is more likely to be a true syrinx that should be evaluated and monitored accordingly.