How To Diagnose Diabetic Peripheral Neuropathy

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Here is a view of preulcerative calluses. When examining patients who may have diabetic peripheral neuropathy, one should perform a complete dermatologic exam including the evaluation of dyshidrosis, callosities, ulcerations and other abnormalities.
Here is a decubitus ulcer that occurred in a patient with diabetic neuropathy who was bed-bound for a brief period. The weight on the heels during this time was significant enough to create the ulcer.
The Semmes-Weinstein monofilament (shown at left) has been proven as an efficient, easy-to-use, inexpensive device for diabetic peripheral neuropathy screening.
The Pressure Specified Sensory Device (shown at right) is reportedly capable of detecting nerve damage earlier than other modalities including nerve conduction velocity examinations.
Some researchers cite the sensitivity and reliability of the biothesiometer or vibrometer for diagnosing diabetic peripheral neuropathy.
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Author(s): 
By Kathleen Satterfield, DPM

The international and multidisciplinary panel was mindful of the limitations of available modalities that might exist in different countries. Accordingly, the panel wanted to develop an easy to follow system that would enable the podiatrist in America to have the ability to reach the same conclusion as the diabetologist in Finland. With that in mind, the International Consensus Group concentrated on developing guidelines that did not require any technologically advanced or expensive equipment to make the diagnosis.5
In regard to the panel’s recommendations for clinicians, it emphasized gathering a comprehensive history of the patient’s symptoms, his or her type of diabetes, the patient’s lifestyle and social circumstances. For the lower extremity exam, the panel recommended a subjective analysis by the examiner that assessed the health status of the skin (i.e., absence of sweating, presence of ulcerations and callosities), immobility of joints, gait and footwear.
The panel recommended that clinicians perform simple tests to assess peripheral sensation. These tests include sensation to pinprick, light touch, vibration (utilizing a 128-Hz tuning fork), pressure and ankle reflexes.

Pointing Out The Flaws Of Simple Tests And Subjective Patient Responses
The International Consensus Group recommended simple and easily available tests for diagnosing DPN but are these tests accurate? Dr. Dyck, a Professor of Neurology at the Mayo Clinic College of Medicine, and others disagree with the group’s findings, citing the system for “major flaws.”1
Dyck points out the shortcomings of the pinprick/tuning fork regimen, noting there are more sensitive and reliable modalities available, such as the biothesiometer or the vibrometer. (However, these modalities are not universally available in all practice settings and this was a requirement of the consensus group.) Dyck also expressed concern about the variability of examiners’ judgment about anthropometric factors of age, gender, height and weight.
In order to make the diagnosis of DPN, Dyck cites the presence of at least two abnormalities from the broad group of neuropathy symptoms, clinical abnormalities and emphasizes the use of nerve conduction, quantitative sensation tests (QST) or quantitative autonomic tests (QAT). This noted neurologist specifies that one of the abnormal findings must be abnormal nerve conduction in at least two separate nerves or an abnormal QAT.1

Dyck’s gold standard is a composite score he calls the “Neuropathy Impairment Score (Lower Limbs) + 7 Tests” (NIS). The NIS is an evaluation of muscle weakness, a decrease or loss of reflexes and a loss of sensation. There are also scores for the patient’s age, gender, physical fitness and anthropometric features. The “seven tests” are peroneal motor nerve conduction, velocity, peroneal compound muscle action potential, peroneal motor distal latency, sural sensory nerve action potential and tibial motor distal latency, heart-pulse rate decrease with breathing and vibratory detection threshold.1
The comprehensive system also includes algorithms for determining a quantifiable score. This quantifiable score leaves little question as to the diagnosis of DPN. However, for what this system offers in specificity, it is an impossibly difficult system for the private practitioner to utilize and would seem better suited for the specialist or researcher who needs the detail for comparison studies.

A Lack Of Reproducible, Objective Techniques
Yet Dyck has a point as the more commonly used examinations (pinprick, reflexes, tuning fork) result in almost entirely subjective findings.1 In addition, the results are often not reproducible, even when these techniques are performed by the same examiner.
There is also the uncertainty of the response by the patient. For a variety of reasons, whether it is an attempt to please, a fear of disease or an inability to understand what is being asked, patients may respond incorrectly either knowingly or unknowingly.

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