Surgery May Help in Diabetic Neuropathy With Squeezed Leg Nerves

Marlene Busko

June 21, 2017

SAN DIEGO — Among patients with diabetic peripheral neuropathy who also had a compressed nerve behind the knee and were in pain despite medical therapies, those who had nerve-decompression surgery had less pain 1 year and 4.5 years later than patients who did not receive surgery.

Results of the Diabetic Neuropathy Nerve Decompression (DNNP) randomized controlled double-blinded prospective study were presented at the American Diabetes Association (ADA) 2017 Scientific Sessions by Shai Michael Rozen, MD, associate professor of plastic surgery at the University of Texas Southwestern Medical Center, Dallas.

Perhaps surprisingly, patients who had sham surgery also reported less pain, although this response was muted compared with the pain relief in patients who had the actual surgery, said Dr Rozen. Moreover, patients who did not have real or sham surgery reported a slight increase in pain over the course of the study, independent of glycemic control.

"These data suggest that there is probably a role for nerve decompression when we think there is a superimposed nerve compression" in a patient with painful diabetic neuropathy, he noted.

This surgery "can alleviate pain, improve quality of life, and probably also reduce opiate consumption, and the results can hopefully encourage further [multidisciplinary] collaborative research," he added.

Asked to comment, session cochair Paul J Kim, MD, from Georgetown University School of Medicine, in Washington, DC, told Medscape Medical News: "This is the most robust study ever done for that procedure, and the fact that they're doing sham surgery, that's unbelievable; that kind of study doesn't get done anymore."

$1 Million Study May Be the Evidence Required

This was a 9-year, $1 million randomized study, initially funded by the National Institutes of Health (NIH), in which 92 patients received decompression surgery in one leg and a sham procedure in the other leg, and 46 patients did not undergo surgery.

In patients with diabetes, "tissues get stiffer," Dr Kim explained. "There is an area right below the fibular head [just below the knee] where the common peroneal nerve comes right across and overlying that is a ligament, and ligaments in patients with diabetes tend to...lose their elasticity, so therefore the nerve gets compressed, [and] you get these symptoms, just like carpal-tunnel syndrome."

Patients who serve as their own controls — in this case, they had decompression surgery in one leg and sham surgery in the other leg — often have a systemic effect and benefit from sham surgery.

However, according to Dr Kim, "honestly, at the end of the day, from a clinician perspective — that's great! I don't have to understand the mechanism. As long as it works, it's fine!"

Nerve-decompression surgery for lower-extremity nerve pain in patients who also have diabetic peripheral neuropathy is not currently reimbursed by Medicare or insurance companies, "because it is unproven."

But when these data are published, they "may push payers over the edge, to say, 'Okay, now there's enough evidence,' " he speculated.

Lower-Extremity Nerve Compression Common

About half of patients with diabetes have painful diabetic neuropathy, and a third of these patients also have nerve decompression, according to Dr Rozen.

Although a few studies have hinted that decompression surgery may ease pain in such patients, the American Neurological Association considers this to be level "U" (unproven) evidence, since the prior studies have been unblinded and lacked a control group and glycemic monitoring.

Thus, the DNND study, conducted by a multidisciplinary team of neurologists, endocrinologists, pain specialists, and neurosurgeons, aimed to investigate the effect of this surgery on pain and quality of life in a more rigorous fashion.

The researchers recruited 2987 adults from the community and screened them with neurological tests and a physical examination.

To be eligible for the study, patients had to have type 1 or type 2 diabetes and pain and/or numbness in both legs despite good glycemic control and/or the use of analgesics, antidepressants, antiseizure medications, transcutaneous electrical nerve stimulation (TENS), or physical therapy.

Importantly, they also had to have a positive Tinel's sign, or distal tingling when the affected nerve is tapped.

The researchers randomized 138 patients 2:1 to surgery or no surgery, and those in the surgery group were blinded as to which leg received the actual nerve-decompression surgery and which received the sham operation.

At baseline, 3, 6, and 9 months, 1 year, and 4.5 years, the patients were evaluated for pain (Likert pain score, from 0 [no pain] to 10 [worst possible pain]), neuropathy, and quality of life (the 36-item Short-Form Health Survey [SF-36] score).

The dropout rate was high. A total of 40 patients in the surgery group and 27 patients in the nonsurgery group were evaluated at 1 year, and 36 patients in the surgery group were evaluated at 4.5 years.

Significant Improvements Starting at 9 Months, Reduction in Opiate Use

At 1 year, compared with baseline, patients in the surgery group reported that on average, pain had decreased by 5.70 on the Likert Score in the leg that had been operated on and by 5.25 in the leg that had the sham procedure (both < .001).

Patients who did not have surgery had a slight continued increase in pain. The pain did not correlate with glucose levels.

Pain continued to decrease over time in the leg that had the actual surgery. At 4.5 years, compared with baseline, patients in the surgery group reported that on average, pain had decreased by 7.47 in the leg that had been operated on and by 5.97 in the leg that had the sham procedure (both < .001).

In the surgery group, the mean general health score (of the overall SF-36) was similar from baseline to 6 months, but this score improved significantly at 9 months and 1 year.

This makes sense, because "you have to remember how long it takes these nerves to regenerate," Dr Rozen observed.

Patients who underwent nerve-decompression surgery had more adverse wound events, but these all healed completely without the need for hospitalization or further surgery.

Moreover, there was a very strong reduction in use of morphine analogs at 4.5 years in patients who had the surgery, although not all patients were treated with these agents.

"We've just started phase 2 of this study last week, for an 8-year follow-up on these patients, [in which] we will look at nerve-conduction studies, [qualified intellectual disabilities (QSPs)], ulcerations, etc," Dr Rozen announced.

And "We do need to better define" subgroups of patients who are likely to respond best to nerve decompression, he concluded.

The study was funded by an NIH grant and by the David Crowley Foundation. Dr Rozen had no relevant financial relationships. Disclosures for the coauthors are listed in the abstract.

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American Diabetes Association 2017 Scientific Sessions; June 10, 2016; San Diego, California. Abstract 102-OR

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