Dilated Central Canal
Dilated Central Canal
What is a Dilated Central Canal?
A dilated central canal, also known as hydromyelia, refers to an abnormal widening or enlargement of the central canal of the spinal cord. This can create a cavity within the spinal cord, leading to pressure on surrounding neural tissue. The central canal is a small, fluid-filled channel that runs through the length of the spinal cord and is part of the central nervous system. While a dilated central canal is sometimes a normal developmental variant in children, in adults, it may signal an underlying issue.
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.
Spinal Cord Anatomy
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.
Dilated Central Canal Treatment
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. For mild cases without significant symptoms, regular monitoring and follow-up imaging may be sufficient.
Dilated Central Canal vs Syringomyelia
A dilated central canal is generally a small, central enlargement of the spinal cord’s normal fluid-filled canal, while syringomyelia involves a larger, abnormal fluid-filled cavity (syrinx) within the spinal cord that can expand and potentially damage surrounding tissue. A dilated central canal is often stable and may not cause symptoms. The distinction is not always straightforward on MRI, and the size, shape, location, progression, and associated symptoms are important when determining clinical significance.
View our conference presentations for more information about dilated central canal:
Dilated Central Canal & Syrinx (Syringomyelia) – Herbert Fuchs, MD
