Neuropathic pain is defined as pain caused by lesions or diseases of the somatosensory system. Management of neuropathic pain is difficult owing to the heterogeneity of underlying causes and absence of objective standards for diagnosis and assessment of neuropathic pain. In this review, we reviewed the recently published guidelines regarding the pharmacological management of neuropathic pain including the French recommendations and the German Neurological Association guidelines, and the American Neurological Association's guidelines for the management of diabetic polyneuropathy. In general, drugs recommended as the first-line treatment for neuropathic pain include gabapentinoid, serotonin–norepinephrine reuptake inhibitor (SNRI), and tricyclic antidepressants. As the second-line treatment, combination of SNRI or tricyclic antidepressant with gabapentinoid could be recommended. Although tramadol and tapentadol are recommended as the second- or third-line treatment, caution is required in long-term use of these medications due to the side effects including dependence and abuse. Besides efficacy, it is necessary to consider the side effects of the medication and underlying disease of the patient in selecting pharmacological treatment.

Background
Clinical spectrum of immunoglobulin M (IgM) monoclonal gammopathy varies from IgM monoclonal gammopathy of unknown significance (IgM-MGUS) to hematological malignancies. We evaluated the clinical features, electrophysiological characteristics, and prognosis of patients with peripheral neuropathy associated with IgM monoclonal gammopathy (PN-IgM MG).
Methods
We retrospectively evaluated 25 patients with PN-IgM MG. Peripheral neuropathy was classified as axonal, demyelinating, or undetermined, based on electrophysiological studies. We classified the enrolled patients into the IgM-MGUS and malignancy groups, and compared the clinical and electrophysiological features between the groups.
Results
Fifteen patients had IgM-MGUS and 10 had hematologic malignancies (Waldenström’s macroglobulinemia: two and B-cell non-Hodgkin’s lymphoma: eight). In the electrophysiological evaluation, the nerve conduction study (NCS) criteria for demyelination were met in 86.7% of the IgM-MGUS group and 10.0% of the malignancy group. In particular, the distal latencies of the motor NCS in the IgM-MGUS group were significantly prolonged compared to those in the malignancy group (median, 9.1 ± 5.1 [IgM-MGUS], 4.2 ± 1.3 [malignancy], p = 0.003; ulnar, 5.4 ± 1.9 [IgM-MGUS], 2.9 ± 0.9 [malignancy], p = 0.001; fibular, 9.3 ± 5.1 [IgM-MGUS], 3.8 ± 0.3 [malignancy], p = 0.01; P-posterior tibial, 8.3 ± 5.4 [IgM-MGUS], 4.4 ± 1.0 [malignancy], p = 0.04). Overall treatment responses were significantly worse in the malignancy group than in the IgM-MGUS group (p = 0.004), and the modified Rankin Scale score at the last visit was higher in the malignancy group than in the IgM-MGUS group (2.0 ± 1.1 [IgM-MGUS], 4.2 ± 1.7 [malignancy], p = 0.001), although there was no significant difference at the initial assessment.
Conclusions
The risk of hematological malignancy should be carefully assessed in patients with PN-IgM MG without electrophysiological demyelination features.

Autoantibodies are present in many autoimmune disorders, including diseases impacting the peripheral nerve, neuromuscular junction, and muscle. Some of these autoantibodies play a vital role in pathogenesis, whereas others are unlikely to be directly pathogenic, but may be useful biomarkers. The identification of autoantibodies is valuable in diagnosis, as well as in establishing a treatment plan in antibody-mediated neuromuscular disorders. This review briefly summarizes antibody, autoantibody, and methods of autoantibody testing for clinicians who treat patients with neuromuscular disorders.