26 years is a long time. Syrinx is just medical slang for syringomyelia. They mean the same thing. In both cases, they refer to an enlargement of the central canal. The current theory that is most commonly accepted today (and one that I think is the best expalnation of the data) is that syringomyelia results from obstruction of cerebrospinal fluid flow at the injury site. Normally, a litter or more of cerebrospinal fluid passes down the spinal cord every day, mostly in the subarchnoid space that surrounds the spinal cord. The arachnoid is the membrane that covers the spinal cord and is responsible not only for holding but also absorbing the cerebrospinal fluid that passes down the spinal cord. Injury often causes adhesions between the spinal cord and arachnoid. Adhesions may obstruct cerebrospinal fluid and divert some of the flow into the central canal that runs in the middle of the spinal cord. The increased flow enlarges the central canal. In some people, the enlarged syringomyelic cavity may compress the spinal cord above and below the injury site.

Diagnosis of syringomyelia requires an MRI, or a CT-myelogram. An MRI can detect a syringomyelic cyst as a high-signal longitudinal cyst in the spinal cord. A plain CT scan typically will not show a syringomyelic cyst because x-rays cannot distinguish between fluid and tissue. However, a CT-myelogram should show a syringomyelic cyst if the dye gets into the cyst. I would trust your SCI doctor's opinion concerning the diagnosis of the syringomyelic rather than a technician's opinion. Your SCI specialist is a surgeon and he is the one who wants to do the surgery? Is she a neurosurgeon? If not, who will the surgeon be? I am puzzled by the surgeon's opinion from Northwestern. Did he look at both the MRI's and CT-myelogram? Are you sure that he said that there was no syringomyelic cyst? Is that doctor an orthopedic surgeon? It seems that your SCI Doctor's was quite firm in her diagnosis.

Now, there is disagreement amongst neurosurgeons whether surgery is necessary or advisable for asymptomatic syringomyelia. Most will not operate if there is no evidence of progressive neurological loss. You describe symptoms that may be consistent with the presence of a cyst but I cannot put together the complex AD and sweating picture that you describe. AD and sweating changes alone are not themselves necessarily due to syringomyelia. However, the fact that you are having intermittent worsening of urinary function is worrisome and would be sufficient reason to operate. Also, it is possible that decompression fo the cyst may restore other functions. Finally, I don't know of many cases where the syringomyelic cyst and neurological loss resolves without surgery.