Kate Johnson
February 6, 2012 (Miami Beach, Florida) — Constant spinal cord stimulation delivered through a permanently implanted device can offer pain relief to patients with HIV-related polyneuropathy that is refractory to conservative treatment, according to Kenneth Candido, MD, and colleagues. Results were presented in a poster here at the 6th World Congress of the World Institute of Pain.
"We believe that it is not only a new indication, but it offers relief for individuals who were previously left to the devices of primary care physicians who really only have at their disposal the ability to prescribe narcotic analgesics," Dr. Candido, who is chair and professor in the Department of Anesthesiology at Advocate Illinois Masonic Medical Center in Chicago, told Medscape Medical News in an interview during the meeting.
Spinal cord stimulation is a well-established technique currently indicated for the management of failed back surgery syndrome, complex regional pain syndrome, inoperable peripheral vascular disease, and refractory angina pectoris, Dr. Candido and colleagues report.
To date, the team has used the technique in 6 patients with debilitating pain from HIV-related polyneuropathy. The first case is described in the poster.
The patient, a 50-year-old man with a 20-year history of HIV, was receiving highly active antiretroviral therapy (HAART). He had an 8-year history of "excruciating" pain.
"He had ongoing severe peripheral neuropathic pain and burning allodynia in both feet, primarily the plantar surfaces. He had not responded to conservative management, which had included high doses of opioid analgesics, anti-inflammatory medications, antiepileptic drugs, and other adjuvants such as peripheral nerve block therapies and epidural injections," said Dr. Candido.
The syndrome of HIV-related pain tends to have a distal "stocking" distribution in the lower extremities, similar to diabetic peripheral neuropathic pain, he explained. "It has been almost exclusively related to pain below the knees. It tends to be bilateral, and we suspect that the mechanism is similar to diabetic peripheral neuropathic pain, in that there is microvascular disruption either due to the virus attacking the vasculature or, alternatively, due to the HAART therapy, which may have a predisposition for the small blood vessels."
After the patient underwent a trial of temporary spinal cord stimulation, in which 2 eight-electrode leads were advanced into the dorsal epidural space and fluoroscopically guided to T9–T10, with good results, a permanent implant was placed.
"He has now had almost 2 years of reduction in his pain, from a constant level of about 8 out of 10 down to about 1 or 2 out of 10, and we've been able to wean him off his opiate analgesics," said Dr. Candido.
On the basis of this initial experience, 5 other HIV patients have received permanent implants, with similar success.
"The beauty of neuromodulation is that we can tailor therapy to the patient's individual symptoms. While I would say that we've used a lumbar approach and lower thoracic stimulators in all patients, clearly not every individual is exactly alike, so we choose our criteria very carefully and we select the actual placement of the stimulators based on the concordant response that we identify during the trial process. We've individualized it, but by and large every individual has responded favorably to T8 through T10 placement of these electrodes."
Dr. Candido explained that as HIV patients live longer because of HAART, the medical community must find pain relief options that are superior to opiate analgesics, which have the potential for extensive adverse effects, including nausea, vomiting, pruritis, constipation, urinary retention, and respiratory depression.
His group has also permanently implanted continuous intrathecal drug delivery systems in 4 HIV patients who did not want spinal cord stimulators.
"Dorsal column stimulation and/or intrathecal delivery of opioids and adjuvants proves to be the primary modality that we believe should be used as a first-line therapy once individuals are identified with this peripheral neuropathic pain process," he said.
Despite the immunocompromised state of HIV patients, he said no adverse events have been reported.
"We know that individuals who have compromised immune status are always predisposed to...infectious processes.... Infections are found in 1% to 2% of individuals who have a dorsal column stimulator, but...in almost two-and-a-half years, we have not identified any superficial or deep infections associated with the permanent implantation process."
Before proceeding, his group studied the orthopedic literature looking at infection rates among HIV patients with hip and knee replacements. "We haven't seen an increase in the incidence of infection in those individuals, so we extrapolated the orthopedic data to our own neurological/surgical population and found that it was logical and intuitive that we should also not have a high level of systemic infection or even localized infection if we took all the appropriate precautions."
Dr. Candido has disclosed no relevant financial relationships.
6th World Congress of the World Institute of Pain: Abstract 171. Presented February 5, 2012.
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