Non-surgical management of low back pain and its electrophysiological assessment

Abstract

Low back pain (LBP) is a major health problem affecting many people. Due to the complicacy of its etiology and potential risks involved in the surgery process, patients are often recommended to get non-surgical management first. In order to relieve the pain, various non-surgical therapeutic interventions (e.g., transcranial direct current stimulation [tDCS], topical anesthetic and functional restoration rehabilitation) are put forward. However, some of these interventions, such as tDCS, still showed no consistent evidence for LBP relief, possibly due to the defects of conventional tDCS electrodes. Meanwhile, although, in our previous study, the patient’s recovery level after functional restoration rehabilitation program could be predicted by using electrophysiology parameters, the prediction result was not good enough. Therefore, in this study, by measuring the pain intensity and electrophysiology (surface electromyography [SEMG] topography and electroencephalography [EEG]), we aimed to investigate the effects of different interventions on LBP and to identify the LBP patient who would respond to the functional restoration rehabilitation program. Firstly, we tried to verify the hypothesis that a single 20-minute session of tDCS on primary motor cortex (M1-tDCS) could relieve chronic low back pain (CLBP) and improve lumbar muscle activities. In order to eliminate the defects of conventional tDCS electrodes, we used dry electrodes. Compared with the patients receiving sham M1-tDCS, the ones receiving real M1-tDCS intervention showed significant decrease of pain intensity (measured by visual analogue scale [VAS]) but no improvement of lumbar muscle activities (measured by dynamic SEMG topography). This result supported part of the hypothesis. Then we compared the effects of M1-tDCS and topical anesthetic on lumbar muscle activities as well as on pain intensity. Findings showed that only the topical anesthetic could alter both the pain intensity and lumbar muscles activities. Because pain consists of bottom-up dimension (sensory-discriminative) and top-down dimension (cognitive-evaluative and affective-motivational), our findings revealed the analgesic mechanism of M1-tDCS on CLBP might be the effect on top-down dimension of CLBP while that of topical anesthetic might be the effect on bottom-up dimension. Our previous assessment of lumbar muscle activities was based on the dynamic SEMG topography during symmetrical flexion-extension trunk-movement. But not all lumbar muscles’ information which contributed to trunk-movement could be shown in this type of SEMG topography. Thus, we needed to expand the type of SEMG topography. It was found the dynamic SEMG topography during asymmetrical trunk-movement could provide additional information for assessment of LBP rehabilitation. Based on the dynamic SEMG topography during asymmetrical trunk-movement and symmetrical trunk-movement, a machine leaning method called support vector machine (SVM) algorithm was proposed to predict the patient who would respond to the functional restoration rehabilitation program. The prediction results showed high accuracy, sensitivity, and specificity. This method will help therapist to recommend the appropriate rehabilitation program to CLBP patients. Last but not least, we also investigated the effect of M1-tDCS on patients receiving lumbar spine surgery. The postoperative pain was relieved after intervention. Assessment results from EEG showed this pain relief might be also led by the modulation to the top-down dimension of pain.