Building a diagnostic algorithm on localized neuropathic pain (LNP) and targeted topical treatment: focus on 5% lidocaine-medicated plaster

Within the broad definition of neuropathic pain, the refinement of clinical diagnostic procedures has led to the introduction of the concept of localized neuropathic pain (LNP). It is characterized by consistent and circumscribed area(s) of maximum pain, which are associated with negative or positive sensory signs and/or spontaneous symptoms typical of neuropathic pain. This description outlines the clinical features (currently lacking in guidelines and treatment recommendations) in patients for whom topical targeted treatment with 5% lidocaine-medicated plaster is suggested as first-line therapy. Few epidemiologic data are present in the literature but it is generally estimated that about 60% of neuropathic pain conditions are localized, and therefore identifiable as LNP. A mandatory clinical criterion for the diagnosis of LNP is that signs and symptoms must be present in a clearly identified and defined area(s). Cartographic recordings can help to define each area and to assess variations. The diagnosis of LNP relies on careful neurological examination more than on pain questionnaires, but it is recognized that they can be extremely useful for recording the symptom profiles and establishing a more targeted treatment. The most widely studied frequent/relevant clinical presentations of LNP are postherpetic neuralgia, diabetic neuropathy, and neuropathic postoperative pain. They successfully respond to treatment with 5% lidocaine-medicated plaster with equal if not better pain control but with fewer side effects versus conventional systemic treatments. Generally, the more localized the pain (ie, the area of an A4 sheet of paper) the better the results of topical treatment. This paper proposes an easy-to-understand algorithm to identify patients with LNP and to guide targeted topical treatments with 5% lidocaine medicated plaster.