Modulation of chronic pain perception with noninvasive

INTERVENTION: Intervention group 1: Subjects receive transcranial direct current stimulation and transcutaneous electrical nerve stimulation only: Transcranial direct current stimulation (Chattanooga Ionto, Tennessee, USA). Dose: 2mA Duration: 30min Mode of administration: 5 consecutive daily sessions (1 session/ treatment day) applied over the dominant motor cortex. Transcutaneous electrical nerve stimulation (Comffit T‐20). Specification: 10Hz, non‐noxious intensity Duration: 30min Mode of administration: 5 consecutive daily sessions (1 session/ treatment day) applied over the bodily site of pain. Transcranial direct current stimulation and transcutaneous electrical nerve stimulation are applied simultaneously during each of the 5 consecutive daily sessions. CONDITION: Chronic musculoskeletal pain PRIMARY OUTCOME: Pain visual analogue scale SECONDARY OUTCOME: Human salivary biomarker (e.g. BDNF) will be collected and measured using immuno‐histo‐chemical techniques. Kessler Distress Psychological Scale (K‐10) Modified Brief Pain Inventory (BPI) Pain Self Efficacy Questionnaire (PSEQ) Patients Global Impression of Change (PGIC) question Perception of participant treatment awareness using visual analogue scales. Sensitivity to electrical body pain stimuli: Electrical stimuli will be delivered to the subject's hand using a constant current stimulator. The subject will be asked to state when they can first ‘detect’ the electrical stimulus. The current intensity (mA) will be recorded. The electrical stimuli will be delivered until the subject can first confidently perceive the stimulus as being ‘painful.’ The current intensity (mA) will again be recorded. The trial will be repeated for a total of three times. The mean of 3 electrical ‘detection’ and ‘pain detection’ thresholds will be calculated. Sensitivity to pressure body pain stimuli: Pressure stimuli will be delivered to the subject's hand using a pressure algometer. The pressure stimuli will be delivered until the subject can first confidently perceive the stimulus as being ‘painful.’ The pressure (kPa) will be recorded. The trial will be repeated for a total of three times. The mean of 3 ‘pain detection’ thresholds will be calculated. Sensitivity to thermal body pain stimuli: For the cold pressor test, the ; subject’s hand will be immersed in ice saturated water (0‐1 degrees ; celcius) to the wrist level, for a maximum of 2 min. The subject will first be ; asked to state when they can first confidently perceive the stimulus as ; being ‘painful.’ This time duration will be recorded. The subject will be ; instructed to withdraw the hand when they feel the pain as intolerable. ; This time duration will also be recorded. A single ‘pain detection’ threshold ; and ‘pain tolerance’ threshold will be calculated. World Health Organisation Quality of life (WHO‐QOL) questionnaire INCLUSION CRITERIA: 1) aged 18‐64, 2) chronic musculo‐skeletal pain (>3 months, prediagnosed) 3) awaiting pain clinic intervention at the Gold Coast Interdisciplinary Persistent Pain Centre