Jared Verdoorn
We chose this research topic because several spine neuroradiologists in our practice had anecdotally noted contrast present in the renal collecting systems when performing CT myelography in patients with spontaneous intracranial hypotension (SIH), and this was not noticed in patients undergoing CT myelography for other indications. We wondered if it was a similar phenomenon to the early appearance of radiotracer activity in the kidneys as is seen in patients with CSF leaks on nuclear medicine cisternograms.
Our findings suggest that contrast in the renal collecting systems on initial CT myelography images is indicative of a CSF leak state, as this finding was only present in patients imaged for SIH. Furthermore, the presence of renal contrast is suggestive of a CSF venous fistula (CVF) as the underlying etiology of CSF leak rather than a dural tear. This has impacted our practice. If a CT myelogram in a patient with SIH demonstrates renal contrast and no dural leak, the exam is reviewed with careful scrutiny for the presence of a CVF. If no CVF is seen, strong consideration is given to proceed to digital subtraction myelography to search for a CVF.
CVF is often an elusive diagnosis on standard CT myelography. Twelve percent of patients with SIH in our study had renal contrast but no evidence of either dural leak or CVF on standard CT myelography. Patients such as these are excellent candidates for digital subtraction myelography, and we have seen progressively increased use of digital subtraction myelography in our practice to attempt to identify CVF.