Interventional, May 13, 2016
Most people with amputated limbs experience phantom limb pain. “However, there is no accepted, effective treatment for these symptoms,” said David Prologo, MD, assistant professor of radiology and imaging sciences at Emory University School of Medicine, in Atlanta, and director of interventional radiology services at Emory Johns Creek Hospital, in Johns Creek, Ga. “The limitless potential of image guidance allows interventional radiologists to access precise areas in the body for treatment.”
Dr. Prologo was lead investigator of a 20-patient pilot study of a new treatment for phantom limb pain—cryoablation—that was presented at the 2016 annual scientific meeting of the Society of Interventional Radiology, in Vancouver, British Columbia. Percutaneous CT and ultrasound guidance were used to precisely place a probe to create “extreme cold to shut down selected nerves,” Dr. Prologo remarked before his presentation. During the 45-minute outpatient procedure, a cryoablation probe was guided through the skin, for a repeated drop in temperature to –40 C. “This creates a targeted ablation zone to arrest nerve signals,” he said.
Patients rated their pain on a visual analog scale, ranging from 1 (not painful) to 10 (extremely painful) at three intervals: before treatment (an average pain score of 6.4), seven days after (roughly 5) and 45 days after the procedure (2.4). “This preliminary data suggests that image-guided nerve cryoablation may be a new therapeutic option for patients with phantom limb pain, a condition that historically has been very difficult to treat,” Dr. Prologo said.
Dr. Prologo said normally nerves in the body carry signals to the brain from the outside. “But in the case of amputations, this neural pathway is interrupted and nerve scars can form neuromas, which results in abnormal nerve firings and the perception of pain in the amputated limb,” he said. “The brain and other nerves also reorganize themselves in an effort to compensate for the missing limb. This is a situation that can result in what we call ‘noise’ from the remaining nerves, which can lead to additional pain.”
By freezing the remaining nerve, “we are able to quiet the noise,” Dr. Prologo said. “This can lead to an overall improvement in symptoms. As a result, patients who have long been told there is no treatment for their pain can have relief through a tiny incision, during a single outpatient visit with a recovery time of 24 hours.”
A patient consultation is first scheduled to document and describe symptoms because often “patients confuse true phantom limb pain with residual limb pain,” Dr. Prologo said. If phantom limb pain is determined, the patient then undergoes a percutaneous CT- or image-guided injection of the numbing anesthetic bupivacaine in order to diagnose the source of the patient’s pain and assess whether the patient’s symptoms improve. “This way we can localize the source of the pain,” said Dr. Prologo.
The procedure consists of placing a probe in an analogous fashion to the diagnostic injection. After 10 minutes of therapy at –40 C, the probe is thawed in place for five minutes, then the temperature reduced to –40 C for an additional 10 minutes, followed by a second five-minute thaw. Afterward, the needle is removed and a bandage placed over the tiny incision.
“It seems very much in my experience that patients subjectively achieve immediate relief in the recovery room from their otherwise constant phantom limb pain,” Dr. Prologo said. The patient is discharged approximately two hours after treatment. Dr. Prologo also believes that therapy is durable at least out to six months and is definitely repeatable.
“When we think about the relief of pain and the epidemic of narcotic overuse and overdosage, possibly figuring out a way to use minimally invasive therapies to reduce pain in certain subsets of populations will potentially reduce the need for and use of narcotics,” said Alan Matsumoto, MD, president of the Society of Interventional Radiology, as well as professor and chair of the Department of Radiology and Medical Imaging at the University of Virginia, in Charlottesville. “A therapy like cryoablation represents using cutting-edge technology to treat patients, but without the cutting.”
Dr. Prologo noted that millions of people in the United States are living with amputated limbs, and according to the Centers for Disease Control and Prevention nearly 200,000 amputations occur each year. “Many of these amputees are our nation’s military veterans, who are severely wounded in combat, and whose reintegration to their civilian lives is limited by pain,” he said. Other causes for surgical amputation include peripheral vascular disease, diabetes and cancer.
“Our study reflects how interventional radiologists can use image guidance to deliver precise, targeted treatment for otherwise difficult-to-manage conditions,” Dr. Prologo said.
—Bob Kronenmeyer
