Background: Psychiatric co-morbidities are common in patients with chronic pain, but no data are available about their prevalence in patients with neuropathic pain. Methods: A multicentre study involving neurology practices (n = 30) and pain departments (n = 8) was conducted to assess the prevalence of lifetime and current anxiety and mood disorders on the basis of DSM-IV criteria in patients with peripheral neuropathic pain. Factors independently associated with such co-morbidity were also studied. A total of 182 consecutive patients (age 59.5 ± 13.8 years, 48% men) were recruited. Assessments included lifetime and current anxiety and mood disorders (Mini International Neuropsychiatric Interview), sleep (Medical Outcome Study sleep scale), pain interference (Brief Pain Inventory) and catastrophizing (Pain Catastrophizing Scale). Results: Lifetime and current prevalence of psychiatric co-morbidity were 39% and 20.3%, respectively, for any anxiety disorder, and 47.2% and 29.7%, respectively, for any mood disorder. The two most common psychiatric disorders were generalized anxiety (current prevalence 12.1%) and major depressive episode (current prevalence: 16.5%). Logistic regression analyses showed that high catastrophizing was the most significant variable independently associated with both current anxiety ; p = 0.04) and mood disorders (OR = 6.9[2.2-21]; p < 0.001). Conclusions: Lifetime and current anxiety and mood disorders are highly prevalent in patients with peripheral neuropathic pain, and are associated with high levels of catastrophizing. Early management of catastrophizing may contribute to reducing the risk of psychiatric co-morbidities in these patients.

Neuropathic pain in SCI patients is a major issue, its determining factors still need to be evaluated properly by refining the epidemiological data.

Purpose Intravenous ketamine is often prescribed in severe neuropathic pain. Oral N -methyl-D-aspartate receptor (NMDAR) antagonists might prolong pain relief, reducing the frequency of ketamine infusions and hospital admissions. This clinical trial aimed at assessing whether oral dextromethorphan or memantine might prolong pain relief after intravenous ketamine. Patients and methods A multicenter randomized controlled clinical trial included 60 patients after ketamine infusion for refractory neuropathic pain. Dextromethorphan (90 mg/day), memantine (20 mg/day) or placebo was given for 12 weeks (n=20 each) after ketamine infusion. The primary endpoint was pain intensity at one month. Secondary endpoints included pain, sleep, anxiety, depression, cognitive function and quality of life evaluations up to 12 weeks. Results At 1 month, dextromethorphan maintained ketamine pain relief (Numeric Pain Scale: 4.01±1.87 to 4.05±2.61, p =0.53) and diminished pain paroxysms ( p =0.03) while pain intensity increased significantly with memantine and placebo ( p =0.04). At 3 months, pain remained lower than at inclusion ( p =0.001) and was not significantly different in the three groups. Significant benefits were observed on cognitive-affective domains and quality of life for dextromethorphan and memantine ( p <0.05). Conclusions Oral dextromethorphan given after ketamine infusion extends pain relief during one month and could help patients to better cope with pain. Future studies should include larger populations stratified on pharmacogenetics screening. Optimization of an oral drug that could extend ketamine antihyperalgesia, with fewer hospital admissions, remains a prime challenge in refractory neuropathic pain.

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