Spinal digital subtraction angiography (SpDSA) is the leading medical imaging procedure for the precise evaluation of blood vessels surrounding the spinal cord. SpDSA is capable of diagnosing an array of spinal vascular disorders, including spinal cord stroke and spinal venous thrombosis. Despite its diagnostic value, SpDSA has a poor reputation when it comes to safety, and there have been reports of complications arising as a result of the procedure.
However, a new study by researchers from the Department of Radiology at the Hopkins School of Medicine shows that SpDSA, previously associated with complications such as stroke and kidney damage, may actually be safe and effective.
In the study reported online in Neurology on Sept. 14, medical imaging experts reviewed the records of patients who underwent SpDSA at the Hopkins Hospital between 2000 and 2010. The researchers found that none of the study participants had suffered a stroke or any kidney damage.
"There was no instance of either complication in more than 300 patients reviewed for our publication, all of whom underwent diagnostic spinal angiography," Philippe Gailloud, M.D., study senior investigator and director of Interventional Neuroradiology at Hopkins, wrote in an email to The News-Letter.
In SpDSA, a catheter tube is inserted into each of the targeted blood vessels near the groin, and threaded into the major arteries branching from the aorta to the spine. A small amount of contrast agent is injected into each artery to help create multiple images taken by the X-ray.
In the 1970s when the procedure was still in its initial stages, preparing patients for testing took hours instead of the half an hour it takes nowadays. This increased the chances that blood clots could form in the blood vessels and lead to a stroke. In addition, more than twice as much potentially toxic contrast dye was used compared to the amount used today.
Gailloud believes improvements in the procedure over the years have made it much safer. "Contrary to a commonly held assumption, spinal angiography has a very low risk of major complications, spinal stroke in particular," he wrote. "This is explained by the improvement in catheters and devices, and the use of new, much safer contrast agents."
The lead study investigator was James Chen, a Hopkins medical student and Doris Duke Charitable Foundation research fellow in Interventional Neuroradiology. Chen began the study with support from experts at the Johns Hopkins Transverse Myelitis Center after noticing that several other specialists and patients were reluctant to use spinal angiography, fearing it was too dangerous.
In addition to establishing that SpDSA is not as dangerous as widely believed to be, the researchers also found that spinal angiography could accurately rule out misdiagnoses of spinal inflammation, also known as transverse myelitis. Out of 45 patients diagnosed with transverse myelitis and treated with steroids or other immunosuppressive agents for the condition, fourteen were confirmed to have a vascular malformation instead upon undergoing SpDSA. These patients were treated for the appropriate condition, and none suffered any complications.
According to Gailloud, both conditions have similar symptoms, so they are easy to misdiagnose without SpDSA. He believes that if a patient is diagnosed with transverse myelitis but fails to show improvement after drug treatment, then the physician and patient should both consider SpDSA in order to rule out the original diagnosis in favor of a vascular malformation.
"Spinal angiography is already the established ‘gold standard' imaging technique for vascular conditions of the spine and spinal cord," Gailloud wrote. "Our findings support a more liberal use of spinal angiography, which is often not considered because of the fear of major complications, spinal stroke in particular, which we showed to be extremely low."
Nevertheless, he believes the procedure should be performed with care and precision. "The fact that spinal angiography should be performed by adequately trained specialists remains valid."
Gailloud and Chen have begun further investigations on the safety of spinal X-rays, monitoring people following SpDSA for any complications for months, or even years, after the procedure. The initial results are expected in 2012, and are likely to shed further light on the safety and efficacy of SpDSA.
