Could a cervical epidural injection have caused my syringomyelia?

Very rare: Syringomyelia from an epidural injection has been reported but typically you would have signs of spinal cord injury directly after the injection (eg., numbness, weakness, or bowel/bladder problems). In my experience I have never seen such a case but it has been reported in the medical literature on a very rare basis.

Rarely...But..: Syringomyelia is usually a developmental problem and rarely caused by trauma. The complication of an expanding space in your neck ( a "syrinx") caused by the trauma of an epidural needle, is extremely rare. I great question for your neurologist or neurosurgeon!

No: A syrinx is usually caused by some sort of trauma to the spinal cord with resulting widening of the central part of the spinal cord. There are several other causes but an epidural injection would not be one of the causes.