Painful diabetic neuropathy: diagnosis and management.

The prevalence of painful diabetic peripheral neuropathy (PDN) is about 20% in patients with type 2 diabetes and 5% in those with type 1. Patients should be systematically questioned concerning suggestive symptoms, as they are not usually volunteers. As PDN is due to small-fibre injury, the 10 g monofilament pressure test as well as the standard electrophysiological procedures may be normal. Diagnosis is based on clinical findings: type of pain (burning discomfort, electric shock-like sensation, aching coldness in the lower limbs); time of occurrence (mostly at rest and at night); and abnormal sensations (such as tingling or numbness). The DN4 questionnaire is an easy-to-use validated diagnostic tool. Three classes of drugs are of equal value in treating PDN: tricyclic antidepressants; anticonvulsants; and selective serotonin-reuptake inhibitors. These compounds may be prescribed as first-line therapy following pain assessment using a visual analogue scale. If the initial drug at its maximum tolerated dose does not lead to a decrease in pain of at least 30%, another drug class should be prescribed; if the pain is decreased by 30% but remains greater than 3/10, a drug from a different class may be given in association.