Functional Near-Infrared Spectroscopy to Assess Central Pain Responses in a Nonpharmacologic Treatment Trial of Osteoarthritis.

BACKGROUND AND PURPOSE: Knee osteoarthritis (OA) is a common source of pain in older adults. Although OA-induced pain can be relieved with analgesics and anti-inflammatory drugs, the current opioid epidemic is fostering the exploration of nonpharmacologic strategies for pain mitigation. Amongs these, transcranial direct current stimulation (tDCS) and mindfulness-based meditation (MBM) hold potential for pain-relief efficacy due to their neuromodulatory effects of the central nervous system, which is known to play a fundamental role in pain perception and processing. METHODS: In this double-blind study, we used functional near-infrared spectroscopy (fNIRS) to investigate the effects of tDCS combined with MBM on underlying pain processing mechanisms at the central nervous level in older adults with knee OA. Nineteen subjects were randomly assigned to two groups undergoing a 10-day active tDCS and MBM regimen and a sham tDCS and MBM regimen, respectively. RESULTS: Our results showed that the neuromodulatory intervention significantly relieved pain only in the group receiving active treatment. We also found that only the active treatment group showed a significant increase in oxyhemoglobin activation of the superior motor and somatosensory cortices colocated to the placement of the tDCS anodal electrode. To our knowledge, this is the first study in which the combined effect of tDCS and MBM is investigated using fNIRS. CONCLUSION: In conclusion, fNIRS can be effectively used to investigate neural mechanisms of pain at the cortical level in association with nonpharmacological, self-administered treatments.

Efficacy of combining home-based transcranial direct current stimulation with mindfulness-based meditation for pain in older adults with knee osteoarthritis: A randomized controlled pilot study.

Transcranial direct current stimulation (tDCS) has been shown to be effective for reducing pain, and a growing body of literature shows the potential analgesic effects of mindfulness-based meditation (MBM). However, few studies have investigated the potential benefits associated with combining tDCS and MBM in older adults with knee osteoarthritis (OA). Therefore, the aim of this study was to examine the feasibility and preliminary efficacy of home-based tDCS paired with MBM in older adults with knee OA. Thirty participants 50-85 years old with symptomatic knee OA were randomly assigned to receive 10 daily sessions of home-based 2 mA tDCS paired with active MBM for 20 min (n = 15) or sham tDCS paired with sham MBM (n = 15). We measured clinical pain and OA symptoms via a Numeric Rating Scale and the Western Ontario and McMaster Universities Osteoarthritis Index. Pressure pain sensitivity and conditioned pain modulation were measured using quantitative sensory testing. Participant satisfaction and side effects were assessed via a questionnaire. Active tDCS paired with active MBM significantly reduced scores on the Numeric Rating Scale and Western Ontario and McMaster Universities Osteoarthritis Index and increased pressure pain thresholds and conditioned pain modulation. Participants tolerated tDCS paired with MBM well without serious adverse effects and were satisfied with the treatment. Our findings demonstrate promising clinical efficacy of home-based tDCS paired with MBM for older adults with knee OA.