Specific syndromes include Postherpetic neuralgia Root avulsions Painful traumatic mononeuropathy Painful polyneuropathy (including neuropathy due to diabetes or chemotherapy) Central pain syndromes (potentially caused by virtually any lesion at any level of the nervous system) Postsurgical pain syndromes (eg, postmastectomy syndrome, postthoracotomy syndrome, phantom limb pain) Complex regional pain syndrome (reflex sympathetic dystrophy and causalgia) Etiology of Neuropathic Pain Neuropathic pain may result from efferent activity (sympathetically maintained pain) or from interruption of afferent activity (deafferentation pain).