The primary purpose is to study the predictive value of preserved nociceptors and large afferent fibers and dynamic mechanical allodynia on the effect of lidocaine patch. The primary outcome measure is the predictive role for these three measures for obtaining a response to lidocaine. A responder is defined as a person with at least a 2-point pain reduction to lidocaine (change in median pain intensity (measured on a 10 point numeric rating scale) of pain from the baseline week to the last week of lidocaine treatment). Secondary effect variable will be efficacy of lidocaine on pain reduction (baseline week versus last week of each treatment) and pain relief (complete, good, moderate, slight, none, or worse) for spontaneous and evoked pain, and effect on ongoing pain, brush evoked allodynia, cold and warm allodynia, and pinprick hyperalgesia evaluated on each visit.