Polyneuropathy with Impaired Glucose Tolerance: Implications for Diagnosis and Therapy.

Prediabetes is associated with a length-dependent polyneuropathy that typically is sensory predominant and painful. A diagnosis of prediabetes should be sought in patients with otherwise idiopathic sensory-predominant neuropathy by doing a 2-hour oral glucose tolerance test. Fasting plasma glucose of 100 to 125 mg/dL or 2-hour glucose 140 to 199 mg/dL (impaired glucose tolerance) constitutes prediabetes. Most patients with neuropathy associated with prediabetes (NAP) are obese and show metabolic manifestations of insulin resistance, including hyperlipidemia and hypertension. Appropriate treatment addresses hyperglycemia, insulin resistance, and neuropathic pain. Professionally administered individualized diet and exercise counseling (modeled on the Diabetes Prevention Program) has been shown to be more effective than glucose-lowering medications in preventing progression from impaired glucose tolerance to diabetes, and is the mainstay of treatment for all patients with NAP. The goals of this therapy should be a 5% to 7% reduction in weight and an increase to 30 minutes of moderate exercise five times weekly. Patients with prediabetes are at increased risk for myocardial infarction, stroke, and peripheral vascular disease. Therefore, risk reduction with control of hypertension and hyperlipidemia is essential. Neuropathic pain troubles nearly every patient with NAP, and often limits aerobic exercise. No trials have specifically addressed the patient population with NAP, and neuropathic pain treatment closely follows recommendations for diabetic neuropathy. Gabapentin, lamotrigine, and tricyclic antidepressants are well-validated first-line therapies. Adjunctive therapy with opioids, nonsteroidal anti-inflammatory drugs often are necessary. Diet and exercise seem to reduce neuropathic pain in patients with NAP.