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Cryoablation Therapy Cools Phantom Limb Pain

April 6, 2016
A new study reports that cryoablation therapy is a safe and effective option for calming phantom limb pain, but results can take up to 45 days to occur.

Interview with J. David Prologo, MD

Over 200,000 limb amputations are performed every year. Many amputees are patients suffering from diabetes, while others are veterans who have incurred devastating wounds during combat.

Phantom limb pain affects many amputees.When a limb is amputated from the body, the neural pathway is interrupted, forcing the brain to reorganize its signals. Typically, this causes phantom limb sensations to occur, which can be a source of significant pain. Up to this point, there has been no blanket treatment to manage these varying effects that develop following an amputation.

“In the absence of a good treatment, what actually happens specifically for veterans…is management of the phantom limb pain using opioids, [which is accompanied by the risks and benefits of] opioid administration, including potential dependence and inability to work and reintegrate into society,” said J. David Prologo, MD, an assistant professor in the Department of Radiology and Imaging Sciences at Emory University School of Medicine in Atlanta, Georgia.

However, interventional radiologists have been developing a promising new treatment—cryoablation therapy—that could offer another option to effectively managing this patient group. Using an image-guided, minimally invasive technique, a small probe is inserted through the skin to target the specific site of scar tissue in the residual limb, which is typically the source of the phantom pain.

“The procedure itself is comparable to other thermal ablation techniques like cooled radiofrequency ablation [C-RFA] or even pulse radiofrequency ablation, in that we use needles to target our region of interest,” Dr. Prologo told Practical Pain Management. However, while those techniques use heat on the target to destroy the lesion, cryoablation instead uses “cold blasts” of pressurized Argon gas to cause a drop in temperature surrounding the probe tip.

Instead of burning the nerves, the cold temperatures shut them off, and the effect appears to reduce nerve damage whilst relieving nerve pain, according to the results of a new study presented by Dr. Prologo and colleagues during the Society of Interventional Radiology’s 2016 Annual Scientific Meeting, held in Vancouver, Canada.1

A Promising New Treatment

The Emory team treated 20 amputees with varying makeups of residual limbs, from the lower extremity (above and below the knee) to the upper extremity (above and below the elbow). All patients received the same uniform procedure, a precise probe insertion through the skin targeting the scar tissue, with the temperature dropped for 25 minutes to create an ablation zone and shut off the nerves.

Patients rated their subjective pain levels on a Visual Analog Scale (VAS) before (baseline), 7 days after, and 45 days after the procedure. Interestingly, the procedure seemed to have had a delayed effect, according to Dr. Prologo. While some patients experienced an immediate difference in pain level, most did not. By day 45, however, the procedure appeared to take effect—baseline average VAS was 6.4 compared with 2.4 points by day 45, a significant improvement. “It was striking to note that during the procedure, many of the patients did not do well until day 30 or 45 days. This is likely to do with the mechanism behind cryoablation’s alteration of the inflammatory response,” Dr. Prologo told Practical Pain Management.

The next question for the researchers is how those patients will fare over the longer 6-month post-intervention period, something Dr. Prologo said he and his team are currently assessing. Another important factor is whether patients would require additional procedures to maintain the anti-nociception over the long-term. At this point, the patient group only received 1 treatment, and it may be possible that additional procedures won’t be necessary, as cryoablation therapy has been successful as a one-shot treatment for other neuralgia patient groups, he said.

Another relevant question is whether certain targeted residual limbs, and other possible confounding factors, can influence the success of cryoablation therapy. With so many questions left to explore, Dr. Prologo and his team have submitted a request for a grant from the Department of Defense for funding to continue researching cryoablation therapy with a much larger patient group.

The investigators would like to see cryoablation "as an alternative to opioids,” Dr. Prologo noted. Interventional radiology at large should be something offered to veterans suffering from related pain syndromes, he elaborated, as the practice presents vital, opioid-sparing alternative treatment options to appropriate patient groups. “This study is really a reflection of a larger application of interventional radiology—it’s a larger reflection of how interventional radiology pioneers these alternatives through the minimally invasive, image-guided approach.”

And given cryoablation therapy’s favorable safety profile—no adverse events or complications were reported, including any infections or cases of hematoma, Dr. Prologo is hopeful further funding will enable his team to investigate the safety and effectiveness of cryoablation for more veterans suffering from phantom limb pain.

This study was conducted by researchers at Emory University and is presented at The Society of Interventional Radiology Annual Scientific Meeting from April 2–7 at the Vancouver Convention Centre, in British Columbia, Canada.

Last updated on: April 6, 2016
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Novel Treatment Device for Phantom-Limb Pain

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