Transcranial direct current stimulation and visual illusion effect according to sensory phenotypes in patients with spinal cord injury and neuropathic pain.
Treatment of neuropathic pain (NP) in patients with spinal cord injury (SCI) remains a major challenge. The aim of the present study is to investigate if the effect of transcranial direct current stimulation (tDCS) combined with visual illusion (VI), following a previously published protocol, has differential effects on pain-related sensory symptoms according to sensory phenotypes profiles. One hundred and thirty SCI patients with NP participated in this open-label trial. Sixty-five patients were given a daily 20-minutes combined treatment of tDCS and VI for 2 weeks. Sixty-five patients served as a control group. Clinical assessment was performed before and 2 weeks later, by using Neuropathic Pain Symptom Inventory (NPSI), Brief Pain Inventory (BPI), and Patient Health Questionnaire-9 (PHQ-9). There was significant improvement in the combined treatment group according to NPSI, BPI and PHQ-9, but no changes in the control group. Following a cluster analysis of NPSI items at baseline assessment, five subgroups of patients with different pain-related characteristics were identified among the treated group, although differences between clusters were not significant. There was also improvement in mood, sleep quality, and enjoyment of life in the treated group. Despite a reduction of NP with the combined treatment, the analysis of sensory phenotype pain profiles does not provide a predictive value regarding the analgesic results of this combined neuromodulatory treatment. Perspective In this article we confirm the analgesic effect of a combined neuromodulatory therapy, transcranial direct current stimulation associated with visual illusion in patients with NP after an SCI. We have identified five clusters of NP with distinct sensory phenotypes, but there was not any specific sensory phenotype cluster that significantly responded to the combined therapy better than the other.