Thalamic deep brain stimulation for neuropathic pain: efficacy at 3 years’ follow-up

Object. Chronic neuropathic pain is estimated to affect 3%- 4,5% of the worldwide population, posing a serious burden to society. Deep Brain Stimulation (DBS) is already established for movement disorders and also used to treat some “off-label” conditions. However, DBS for the treatment of chronic, drug refractory, neuropathic pain, has shown variable outcomes with few studies performed in the last decade. Thus, this procedure has consensus approval in parts of Europe but not the USA. This study prospectively evaluated the efficacy at 3 years of DBS for neuropathic pain. Methods. Sixteen consecutive patients received 36 months post-surgical follow-up in a single-center. Six had phantom limb pain after amputation and ten deafferentation pain after brachial plexus injury, all due to traumas. To evaluate the efficacy of DBS, patient-reported outcome measures were collated before and after surgery, using a visual analog scale (VAS) score, University of Washington Neuropathic Pain Score (UWNPS), Brief Pain Inventory (BPI), and 36-Item Short-Form Health Survey (SF-36). Results. Contralateral, ventroposterolateral sensory thalamic DBS was performed in sixteen patients with chronic neuropathic pain over 29 months. A postoperative trial of externalized DBS failed in one patient with brachial plexus injury. Fifteen patients proceeded to implantation but one patient with phantom limb pain after amputation was lost for follow-up after 12 months. No surgical complications or stimulation side effects were noted. After 36 months, mean pain relief was sustained, and the median (and interquartile range) of the improvement of VAS score was 52.8% (45.4%) (p=0,00021), UWNPS was 30.7% (49.2%) (p=0,0590), BPI was 55.0 % (32.0%) (p=0,00737) and SF-36 was 16.3% (30.3%) (p=0,4754). Conclusions. DBS demonstrated efficacy at 3 years for chronic neuropathic pain after traumatic amputation and brachial plexus injury, with benefits sustained across all pain outcomes measures and slightly greater improvement in phantom limb pain. of the neurosurgical treatment given. The Visual Analog Scale (VAS) to rate pain intensity, the University of Washington Neuropathic Pain Score (UWNPS), and Brief Pain Inventory (BPI) were used. A 36-Item Short-Form HealthSurvey (SF-36) on quality of life along with the pain questionnaires were also completed by patients. The SF-36 responses were regrouped into 8 domains of physical functioning: role (physical), bodily pain, general health, vitality, social functioning, role (emotional), and mental health. Results were scored by online tools (http://www.sf-36.org/demos/sf-36.html). Norm-based scores allowed comparison between studies. Wallis test one-way ANOVA) on the normalised data for each test score of The null hypothesis of the Kruskal Wallis test the group median of the tested score at each time point came the same distribution. In tests where p was less than 0.05, multiple comparison tests using a Tukey-Kramer method were performed to compare individual group medians at each time point to assess which scores at which time points differed significantly from the preoperative score, with a p-value < 0.05 considered statistically significant and p < 0.01 considered highly significant. All data is presented as median + interquartile range.