Current And Emerging Tools For Assessing Diabetic Peripheral Neuropathy

Maria K. Piemontese, DPM, and Andrew J. Meyr, DPM
   Autonomic dysfunction presents with significant lower extremity and systemic effects. Edmonds and co-workers studied an interesting facet of autonomic neuropathy in three groups of patients.18 They found that heart rate during deep breathing and stance was significantly slower in diabetic patients with foot ulceration in comparison to normal controls and diabetic patients without a history of foot ulceration. The authors concluded that severely abnormal autonomic function occurs in association with neuropathic foot ulceration but patients without ulcers have lesser degrees of autonomic neuropathy.    Another condition to be aware of is known as “hypoglycemic unawareness.” During this, a patient does not experience the normal symptoms of hypoglycemia (sweating, rapid heartbeat) that act as a warning system.

What Are The Best Methods Of Detecting Neuropathy?

It is well accepted that peripheral neuropathy is a risk factor for developing foot ulceration and that early detection leading to adequate foot care can reduce amputation rates by about 50 to 80 percent.19 This emphasizes the need for assessment tools that are simple, objective, reproducible and comprehensive. How well are we doing in this respect?    The simplest and likely most frequently utilized instrument for assessing neuropathy is the Semmes-Weinstein (SW) monofilament. Lee and colleagues attempted to determine the reliability of the SW monofilament in patients with diabetes.20 They applied the monofilament to the 10 recommended sites and found the sensitivity and specificity of the plantar metatarsal region to be 93 percent and 100 percent respectively. Other studies have confirmed their conclusion that the device is a sensitive, specific and inexpensive screening tool for identifying diabetic peripheral neuropathy.21,22    A critique of this instrument is its fairly limited scope. It is unable to quantify or stage a level of neuropathy, and also does not provide any information about the motor and autonomic components of the disease process.    One should fully assess motor neuropathy and autonomic neuropathy during an examination, but this can represent a challenging problem when attempting to have objective and reproducible results.    One means for attempting to quantify all components of diabetic peripheral neuropathy is the Michigan neuropathy screening instrument (MNSI). This consists of a history portion that the patient completes and a physical exam portion that the healthcare professional completes. The patient portion consists of 15 questions such as “Are your legs and/or feet numb?” and “Are you able to sense your feet when you walk?” The exam portion looks at such factors as appearance (deformities, calluses, etc.), ulceration, ankle reflexes, vibration perception at the hallux and monofilament detection.23,24    This simple screening test encompasses all sensory, motor and autonomic components of neuropathy, and allows for a quantitative and objective measurement. The developers of the instrument have found it to be sensitive and reproducible for screening and diagnosis.    Moghtaderi and co-workers assessed the validity of the MNSI and aimed to determine the diagnostic performance of the test characteristics for the diagnosis of peripheral neuropathy.25 This study found that the accuracy of the MNSI made it a useful screening test for diabetic neuropathy. In deciding which patients one should refer to a neurologist or for electrophysiological studies, the authors specifically suggested a cutoff score of “2” during the physical examination portion for diagnosis and referral.

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