When Patients With Diabetes Have Lower Extremity Nerve Entrapments

Editor’s note: Peripheral nerve decompression for patients with diabetes and lower extremity neuropathy continues to be a hotly debated topic in podiatric medicine and other specialties. The driving force of evidence based medicine has looked critically upon this procedure while many respected surgeons in a variety of fields have found great clinical successes. Dr. Mowen reviews many of the debate topics and presents some helpful information and opinion in this column. — Dr. Steinberg    It has long been recognized that patients with diabetes experience a higher rate of carpal tunnel syndrome (CTS) than those without diabetes.1,2 Anecdotally, most family doctors, endocrinologists and neurologists seem to agree that upper extremity entrapments are very common among patients with diabetes.    In my clinical experience, many of those same physicians do not recognize that patients with diabetes have a higher rate of lower extremity entrapments like tarsal tunnel syndrome. Lower extremity nerve pain and neuropathic symptoms are often too readily diagnosed as peripheral neuropathy and practitioners do not look for treatable entrapments.    It is theorized that sorbitol will build up in the peripheral nerves, causing an increase in the osmolar properties and subsequently swelled nerves. Nerves will then become entrapped in tight anatomical areas such as the carpal tunnel. Entrapments will cause a decrease in axoplasmic flow and a decrease in the microcirculation of the nerve.3    Accordingly, it seems sensible that this same process is also occurring in the lower extremity, perhaps even to a much greater degree due to the mechanical stress in the legs and feet. Often, the lower extremity has poorer circulation compared to the upper extremity. High-resolution ultrasound has shown the posterior tibial nerve to have a greater diameter in diabetic peripheral neuropathy (DPN) in comparison to patients without diabetes.4    With swollen nerves, it seems only logical there will be more pressure on the nerves in tight anatomical locations. The tibial nerve and its branches are compressed in the tarsal tunnel and within the porta pedis. The common peroneal gets trapped at the fibular head under the fascia of peroneus longus and the deep peroneal nerve on the dorsum of the foot under the extensor digitorum brevis tendon. These multiple sites cause the “multiple crush” phenomenon and can lead to a symmetric polyneuropathy. The theory of triple or multiple compression has been the basis of triple decompression surgery to treat DPN.

A Closer Look At Surgical Decompression For DPN

Surgeons affiliated with Johns Hopkins University have been operating on DPN for almost 20 years. A. Lee Dellon, MD, the pioneer of this work, first published his results in 1992.5 However, Dellon’s work is still received skeptically by many within the medical community. The American Association of Neurology cannot recommend this procedure because there are not enough studies.6 Yet the American Association of Neurology has no problem having patients undergo carpal tunnel, cubital tunnel or radial sensory releases. The bottom line is many patients with diabetes and neuropathy probably have superimposed nerve entrapments in both the upper and lower extremity.    The surgery to decompress peripheral nerves is fairly easy as it involves only soft tissue releases. The most common procedure involves release of the common peroneal nerve at the fibular head, the deep peroneal on the dorsum of the foot, and the tibial nerve and its branches in the tarsal tunnel. Most patients are going to tolerate the procedure very well. Many will have improved sensation and decreased pain while they are still in the recovery room.    Although this procedure is fairly easy to perform, about 300 surgeons from all backgrounds are performing this “triple” decompression. It is strongly recommended that one should learn the procedure from someone trained at the Peripheral Nerve Institute at Union Memorial Hospital in Baltimore. The institute also offers an intense workshop with cadaver surgery and observation of live procedures.

Can The Procedure Have An Impact?

We see patients every day with various levels of neuropathy. In the past, we have been told it is a progressive disease that we can only treat by controlling the underlying cause and providing a battery of pain relievers (anticonvulsants, etc.).    No one disagrees on treating the underlying cause. However, with few exceptions, we have watched those patients go on a downward spiral. For 18 years now, I have been treating lower extremity complications in patients with diabetes and watch patients with neuropathy go from having a little numbness and tingling to developing ulcers, nasty infections, Charcot, amputations, etc. In 1999, there were 92,000 amputations directly linked to DPN in comparison to 54,000 in 1990.7 The cost alone of these complications is staggering. I wish I could go back and reevaluate those patients, and see how many had nerve entrapments that could have been treated before the problems became irreversible.    It is true there are not any very large, double-blinded studies on the surgical treatment of DPN. One interesting study in the Annals of Plastic Surgery in 2004 retrospectively looked at 50 patients who only underwent surgery on one limb. With an average follow up of 4.7 years, researchers found none of these limbs developed ulcers or were subject to amputations. The nonoperative limbs had 12 ulcers and three amputations, according to the study.8

Factors To Consider In Proper Patient Selection Or Referral

Prudent surgeons will weigh many factors when deciding which patients are suitable surgical candidates. I am certainly not advocating surgery for every patient with neuropathy. However, I do advocate looking for entrapments that may be present and responsible for a patient’s diabetic neuropathy.    Check for Tinel’s sign on the posterior tibial nerve and/or the common peroneal. Researchers have found that if there is a positive Tinel’s sign, there is a 93 percent chance of an excellent outcome with surgery. Without a positive Tinel’s sign, the odds drop to about 50 percent.9 Sensory testing is still the most reliable diagnostic procedure in comparison to nerve conduction velocity (NCV).10 Obtaining EMG and/or MRI might also be necessary to rule out a more proximal lesion.    All physicians work within their own personal comfort zones. We should all know what is available to our patients and be willing to refer patients if their care falls outside of our comfort zone. I think a great number of patients suffering from neuropathy would benefit from an evaluation and treatment for multiple compression problems.    Dr. Mowen runs a lower extremity neuropathy clinic in Ventnor, NJ. He is board certified in podiatric orthopedics and primary podiatric medicine. He is an Associate Member of the Academy of Ambulatory Foot Surgeons and a Member of the Fellowship of Peripheral Nerve Surgeons.    Dr. Steinberg (pictured at left) is an Assistant Professor in the Department of Plastic Surgery at the Georgetown University School of Medicine in Washington, D.C.
 

References:

References 1.    Perkins B, Olaeye D, Bril V. Carpal tunnel syndrome in patients with diabetic polyneuropathy. Diabetes Care 2(3), March 2002. 2.    Tanaka S, Wild D, Seligman P, et al. The US prevalence of self-reported carpal tunnel syndrome: 1988 National Health Interview Survey Data: Am J Public Health. 3.    Jakobsen J, Sidenius P. Decreased axonal transport of structural proteins in streptozocin diabetic rats. J Clin Invest 66:292, 1980. 4.    Kincaid BR, Barrett SL. Use of high-resolution ultrasound in evaluation of the forefoot to differentiate forefoot nerve entrapments. J Am Podiatr Med Assoc 2005 95: 429-432. 5.    Dellon AL. Treatment of symptoms of peripheral neuropathy by peripheral nerve decompression. Plast Reconstr Surg 1992; 89: 689-697. 6.    Chaudhry V, Stevens JC, Kincaid J, So YT. Practice Advisory: Utility of surgical decompression for treatment of diabetic neuropathy (Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology). Neurology 2006;66:1805-1808. 7.    Bloomgarden ZT. American Diabetes Association 60th Scientific sessions, 2002 The Diabetic Foot. Diabetes Care. 2001;24; 946-951. 8.    Aszman O, Tassler P, Dellon AL. Changing the natural history of diabetic neuropathy. Incidence of ulcer/amputation in the contralateral limb of patients with unilateral nerve decompression. An Plast Surg 53(6), Dec 2004. 9.    Dellon C, Dellon AL. Prognostic ability of Tinel sign in determining outcome for decompression surgery in diabetic and non-diabetic neuropathy. An Plast Surg 53(6), Dec 2004. 10.    Siemionow M, Zielinski M, Sari A. Comparison of clinical evaluation and neurosensory testing in the early diagnosis of superimposed entrapment neuropathy in diabetic patients. An Plast Surg 57(1), July 2006.