Painful peripheral neuropathy

Painful peripheral neuropathy (PPN) is characterized by neuropathic pain (NP), which is accompanied by dysfunction of motor, sensory and autonomic nervous system. It always involves small nerve fibers, including A δ and C fibers. PPN can be classified into two types according to etiology: hereditary and acquired. Pain of PPN can manifest as spontaneous pain and stimulus-evoked pain (allodynia, hyperalgesia and hyperpathia). The manifestation of typical cases is length-dependent, which firstly involves the feet, and then progresses proximally and to the hands, presenting a glove-stock pattern. PPN can be either an isolated disease entity or part of other diseases. The former indicates idiopathic small fiber neuropathy (SFN), while the latter contains various diseases involving peripheral nerve fibers, including systemic diseases such as diabetes mellitus and peripheral neuropathy with other causes. The accessory examinations of PPN include quantitative sensory testing (QST), intraepidermal nerve fiber density (IENFD), sympathetic skin response (SSR), etc. Among them, IENFD is the "golden standard" for SFN. The major therapeutic methods are to control primary diseases and relieve pain. Medications alleviating neuropathic pain consist of carbamazepine, pregabalin, gabapentin and amitriptyline, etc.