The aim of this study is to evaluate the cortical excitability in pain of knee osteoarthritis (OA), as well as the effect of one session of a kind of electroacupuncture (deep needling intramuscular stimulation therapy - DIMST) in this pain and the cortical excitability after the intervention. The hypothesis is that cortical excitability is altered in this condition, confirming the findings already described in other chronic pain conditions. The investigators also believe that a session DIMST can reduce pain and alter cortical excitability, restoring its previous activity will occur from chronic pain.
Recent developments in the treatment of chronic pain have shown that the primary motor cortex (M1) is an effective target for neural brain stimulation techniques, such as transcranial magnetic stimulation (TMS). Due to these promising initial results, the plasticity of M1 has also been investigated as a potential marker for chronic pain. TMS studies using single or paired pulse shown changes in M1 plasticity in neuropathic pain and fibromyalgia pain compared to healthy subjects. Thus, there is a decrease in the inhibitory activity of chronic pain that can take a state as shown uninhibited by measuring TMS indexed intracortical inhibition (ICI) and cortical silent period (CSP). Based on these experimental data and clinical studies have been focused on the effects of neuromodulation techniques in M1 excitability. The techniques used to stimulate the peripheral nervous system was investigated using different approaches. The DIMST is a therapy applied to treat peripheral chronic syndromes that may have central components such as myofascial pain. During DIMST, the needles are applied to the spinal segment associated with nerve roots dermatome corresponding to the pathology. This treatment can also be effective in the treatment of diseases that have major peripheral components such as OA. OA is a major cause of suffering and disability in the elderly, having an inflammatory component, such as a factor that contributes to the symptoms and progression of the disease. There is evidence that OA could lead to sensitization central and segmental, but these effects on M1 plasticity and other central components are not completely known. Therefore, researchers proposed to evaluate the plasticity of M1 in this chronic pain condition and also the effect of bottom-up DIMST in pain and cortical excitability.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
26
The investigators used electro acupuncture of 2 Hz during 30 minutes.
Electro acupuncture with rubber electrodes, without current passing.
Hospital de Clínicas de Porto Alegre.
Porto Alegre, Rio Grande do Sul, Brazil
Pain Pressure Threshold (PPT) After Intervention..
PPT (alone): The patient was instructed to verbally report the perception of pain onset. The investigator assessed PPT using an electronic algometer (J Tech Medical Industries, USA). The device had a 1-cm2 hard-rubber probe, which was applied over structures at L1- L5 dermatome at the knee and at the contralateral forearm. The average values of PPT in kgf/cm2 for three successive readings taken at intervals of 3-5 min were used as the outcomes. \# Below, the data after intervention.
Time frame: Before and within one hour after intervention.
Motor Evoked Potential (MEP) After Intervention.
Cortical excitability was assessed using a MagPro X100 (MagVenture Company, Lucernemarken, Denmark) and a figure-of-8 coil centered over the left motor cortex (M1). Subjects were seated in a comfortable reclining chair with their arms and hands lying relaxed on the armrests. The investigators measured the resting motor threshold (rMT) of the right first dorsal interosseous (FDI) muscle. The MEPs were recorded by surface electromyography (EMG) using Ag-AgCl cup electrodes in a belly tendon montage. Resting motor threshold (rMT) was defined as the stimulus intensity at which peak-to-peak MEP amplitude of 50 µV (microvolts) was obtained in at least 5 of 10 consecutive trials. MEP was defined as approximately 130% of the rMT or the stimulus intensity at which peak-to-peak MEP amplitude of at least 1 mV was obtained in 10 consecutive trials. The result of the MEP was the average of 10 curves (unconditioned MEP). \# Below the data after intervention.
Time frame: Before and within one hour after intervention.
Conditioned Pain Modulation (CPM) After Intervention.
PPT during cold water immersion (PPT+CPM): By measuring PPT during cold water immersion, we evaluated the degree to which pain perception is modulated by conditioned pain modulation (CPM) following the presentation of an initial heterotopic noxious stimulus. Subjects immersed their left hands into cold water (zero to 1°C) for 1 minute. During the last 30 seconds of cold-water immersion, the PPT procedure was administered at the right forearm. The temperature was held constant across during the experiment for each subject. \# Below the data after intervention.
Time frame: Before and within one hour after intervention.
Intracortical Inhibition (ICI) After Intervention.
ICI was evaluated using inter-stimuli intervals (ISIs) of 2 ms with paired-pulse stimulation. The subthreshold stimulus was set at 80% of rMT (conditioning stimulus) , and the suprathreshold test stimulus was set at 130% of rMT. After a randomized protocol, thirty stimuli were assessed using a 2ms interval (ICI), a 12ms interval (ICF) and test-only trials (MEPs). The resulting MEP amplitude was converted into the mean amplitude, and paired-pulse parameters were expressed as the amount of inhibition or facilitation. The calculation result of ICI was done by the ratio of the mean ICI by the mean MEP. \# Below the data after intervention.
Time frame: Evaluated in one day. The cortical excitability before and within an hour after intervention.
Pain Intensity After Intervention.
The intensity of pain was measured by a 10-cm VAS. VAS scores ranged from no pain (zero) to the worst possible pain possible (10 cm). The pain score on VAS during the last 24 hours was used to classify the subjects into two groups: (1) absence of pain or mild pain (scores equal to or lower than 4 cm) and (2) moderate, intense, or worst possible pain (scores higher than 4 cm). \# Below the data after intervention.
Time frame: Evaluated within twenty four hours before and within one hour after the intervention.
Intracortical Facilitation (ICF) After Intervention.
ICF was evaluated using an inter-stimuli intervals (ISIs) of 12 ms with paired-pulse and similar parameters for the conditioning and test stimuli. After a randomized protocol, thirty stimuli were assessed using a 2ms interval (ICI), a 12ms interval (ICF) and test-only trials (MEP). The resulting MEP amplitude was converted into the mean amplitude, and paired-pulse parameters were expressed as the amount of inhibition or facilitation. The calculation result of ICF was done by the ratio of the mean ICF by the mean MEP. \# Below the data after intervention.
Time frame: Before and within one hour after intervention.
Cortical Silent Period (CSP) After Intervention.
To determine the cortical silent period (CSP), subjects were instructed to squeeze the dynamometer using their fingers at 20% of maximal force when a single pulse stimulus (130% rMT) was applied. The result was the average of five consecutive measurements. The CSP was determined by the interval between the stimulus and the motor response elicited in the subject. \# Below the data after intervention.
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Time frame: Evaluated before and within one hour after intervention.