Correlation Between DNA Methylation of TRPA1 and Chronic Pain States in Human Whole Blood Cells.

OBJECTIVES: Neuro-immune interactions with functional changes in the peripheral blood cells including changes in the transient receptor potential ankyrin 1 (TRPA1) appear to play a pivotal role in the development of chronic pain in humans. The aim of this study was to examine the association between TRPA1 DNA methylation in whole blood cells and the pain states in chronic pain patients. METHODS: After collecting blood samples from 12 chronic pain patients, the authors measured DNA methylation levels in whole blood cells. Significant associations between the patient's demographic data and the chronic pain states were determined by a multiple linear regression analysis that used age, body mass index, pain duration, depression, anxiety, cognitive impairment, activities of daily living, neuropathic pain, and pain states as the dependent variables, and the TRPA1 DNA methylation levels as the independent variables. RESULTS: Multiple regression analysis revealed a significant correlation between increases of the methylation levels of the CpG island in the TRPA1 gene and increases in the number of neuropathic pain symptoms, which were evaluated using the Douleur Neuropathique 4 (DN4) questionnaire. Decreases in the TRPA1 mRNA expression were also significantly related to increases in the DN4 score. The presence of a burning sensation, which is one of pain symptoms in the DN4 questionnaire, was significantly correlated with the increase in DNA methylation level of TRPA1. CONCLUSIONS: TRPA1 DNA methylation levels in whole blood cells appear to be associated with pain symptoms in chronic pain patients.

Spinal cord stimulation for treatment of leg pain associated with lumbar spinal stenosis.

OBJECTIVE: Spinal cord stimulation (SCS) is expected to have analgesic effects in patients with neuropathic pain, ischemic pain, or mixed pain. The type of leg pain caused by lumbar spinal stenosis (LSS) is considered as mixed pain, which is expected to respond to SCS. However, there is no established view on the usefulness of SCS in the management of this type of pain. Therefore, we aimed at evaluating the efficacy of SCS against leg pain associated with LSS. MATERIALS AND METHODS: Data were collected retrospectively for the period from January 2003 to December 2011 from 91 patients with LSS-associated leg pain enrolled to the SCS trial. SCS implantation was performed in patients who responded to the trial and desired to receive this therapy. RESULTS: The response rate (percentage of patients showing 50% or greater alleviation of pain) in the trial was 65% (59/91 patients). SCS implantation was performed on 41 patients. The percentage of patients who showed a good response (definition is SCS continued for one year or longer after implantation) was 95% (39/41). CONCLUSION: SCS seemed to be effective against leg pain associated with LSS. Thus, SCS should be actively adopted in indicated patients as a method of treatment intermediate between conservative therapy and surgical therapy.