Dry Needling Effects on Cortical Excitability

Research Design:

This study will be pre-test post-test trial, in which all eligible participants will receive a single session of dry needling (DN). All outcome measures will be collected before and immediately after a single session of DN.

Procedure:

Eligible participants will be asked to complete an intake form, asking them about their demographic data, including age, gender, height, weight, occupation, past medical history, and questions related to their low back pain (onset, injury mechanism if any, location, duration, type, and nature). Once the participant's eligibility is confirmed, each participant will complete the Central Sensitization Inventory (CSI) questionnaire to assign each participant either in the CS group or non-CS group using the 40 cutoff score of the CSI.

1. Clinical Assessments: Each participant will complete 3 self-reported questionnaires before cortical excitability assessment, including pain intensity determined using the Numeric Pain Rating Scale (NPRS), disability determined using the Modified Oswestry Low Back Pain Disability Questionnaire (modified ODI), and quality of life determined by the Patient-Reported Outcomes Measurement Information System® -short form (PROMIS-29). These questionnaires will be used to describe the characteristics of the participants in this study.
2. Cortical Excitability Assessment: Three cortical excitability parameters will be collected: amplitudes of motor evoked potentials (MEPs), intracortical facilitation (ICF) values, and short-interval cortical inhibition (SICI) values. Participants will lie in a prone position for the electromyographic (EMG) setup. EMG activity will be collected from the painful side of the L4-5 area. Following the recommendations of the Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles (SENIAM) project, the electrode for the LM will be placed at the L4-5 level, approximately 2-3 cm from the midline, and will be aligned with a line from the posterior superior iliac spine (PSIS) to the interspace between the L1 and L2 spinous process. To obtain MEPs of the LM muscle, the M1 (primary motor cortex) will be stimulated while the participant performs a submaximal voluntary contraction. First, the maximum voluntary isometric contractions (MVIC) of the LM will be determined. During the MVIC testing, each participant will perform the maximum upper extremity and trunk lift with the elbows flexed to approximately 90° and shoulders abducted to approximately 120°, and maintain the lift for 3 seconds while resisting against a load applied at the opposite elbow of the painful side by the testing investigator. Two trials each will be performed and the highest root mean square (RMS) of EMG amplitude will be identified. During the cortical excitability assessment, a target line representing ~ 20% of highest RMS value during MVIC will be placed on the real-time EMG monitor while the participant will be asked to maintain the target LM activation by slightly leaning forward and to maintain lumbar lordosis in a seated position. Following the MVIC testing, each participant will be seated on a chair for cortical excitability assessment. A "hot spot" will be determined while the participant maintains a 20% submaximal contraction of the LM (i.e., slightly leaning forward and maintain lumbar lordosis). A hot spot is defined as the site at which the largest MEP amplitude is obtained at the lowest TMS stimulation intensity or output (0-100%). The double-cone coil will be positioned over the M1 area opposite to the participant's most painful side. The intensity of TMS stimulation from one TMS stimulator will begin at 35% of stimulator output and then will be increased gradually to yield a MEP from the LM until a 'hot spot' is observed. Next, the active motor threshold (AMT) will be determined. AMT is defined as the stimulation intensity which yields a peak-to-peak amplitude of MEP larger than 200 μV in 5 out of 10 consecutive trials. Once the AMT is determined, the stimulation intensity will be set at 130% of AMT and 10 stimulations will be delivered to the hot spot. The 10 supra-threshold MEP amplitudes (uV) recorded from the LM will be averaged and the average will be used for statistical analysis. For the ICF and SICI testing, two stimuli, one conditioning stimulus and one test stimulus, will be generated from two TMS stimulators connected by a coil (BiStim Module, Magstim Co., UK). In ICF, a subthreshold conditioning (second) TMS at the 90% AMT will be delivered to the hot spot 15 ms after a test (first) TMS at the 100% AMT. In SICI, a subthreshold conditioning TMS at 70% AMT will be delivered 2 ms before a test TMS at a supra-threshold test TMS at 120% AMT. For both ICF and SICI, the amplitude of the conditioned MEP will be expressed relative to the amplitude of the corresponding test MEP. Ten trials will be performed for each of the ICF and SICI tests, and the average of the 10 trials will be used for statistical analysis.
3. Quantitative Sensory Tests (QSTs): The two QSTs, pressure pain thresholds (PPTs) and conditioned pain modulation (CPM) tests, will be administered after the cortical excitability assessments both before and after the DN intervention. During the PPT, participants will be given a response button to stop testing on their own, and will be instructed to stop the test as soon as the pressure becomes uncomfortable or painful, and not to allow an uncomfortable or painful sensation to continue. Four trials will be tested on the most tender point around L4-5, but the first trial will be counted as a practice trial. The average of the last three trials will be used for statistical analysis. For the CPM test, a thermode will be applied to the most tender point of the low back and then heat temperature will increase at 1°/sec to the point until the participant perceives the heat stimuli painful at 6/10 on the numeric pain rating scale (NPRS). Two thermodes which generate heat stimuli at the temperature that the participant rates 6/10 on the NPRS will be used for the CPM testing, one applied to the most tender point of the low back (test stimulus), and the other on the contralateral side of forearm (conditioning stimulus). The NPRS scores will be collected under the two conditions: test stimuli alone and combined test stimuli and conditioning stimuli. The test stimuli will be applied first for 10 seconds and then the conditioning stimuli for 25 seconds, so that the second application of the testing stimuli (for 10 seconds) would occur after 15 seconds of conditioning stimuli.
4. Dry Needling Intervention: Two lengths of sterile, disposable, 0.30 mm x 60 mm solid filament needles (Seirin Corp., Shizuoka, Japan) and 0.30 mm x 100 mm solid filament needles (Shanghai Kangnian Medical Device Co., Ltd., Shanghai, China) will be used in the study. The length of the needle for each participant will be selected based on the size of the participant. Two needles will be inserted on or near the most tender point of the low back. Two additional needles will be inserted on the opposite side at the level of the most tender point regardless of unilateral or bilateral LBP. After piercing the skin, the needle will be directed toward the spinous process in a slight inferior-medial angle (approximately 20-30°). Once the needle is inserted, the treating investigator will use ultrasound (US) scanner to visualize the needle placement and to confirm that needle has reached the deeper layer of the LM. Once the needle placement is confirmed, it will be pulled slightly in and out within the muscle and redirected in small angles for 10 seconds after insertion. The needles will stay (in situ) in the LM for approximately 10 minutes after the insertion and then will be withdrawn.
5. Statistical Analysis:

Descriptive statistics will be calculated for participant characteristics as well as baseline outcome measures (amplitudes of MEPs, ICF values, SICI values, PPTs, and CPM scores) of all participants. Independent t-tests will be used to compare the ratio data of participant characteristics, self-reported questionnaires, and baseline outcome measures between the two groups. Chi-square statistics will be used to analyze categorical data of participant characteristics (e.g., sex, side(s) of pain, testing side).

The statistical analysis used to address the three aims with the alpha level is set at 0.05 for all statistical analyses: 1) three paired-t tests or Wilcoxon signed rank tests for the three cortical excitability variables (amplitudes of MEPs, ICF values, and SICI values), respectively, 2) two paired-t tests or Wilcoxon signed rank tests for the two neurosensory variables (PPT and CPM values), respectively, and 3) three 2 (group) x 2 (time) repeated measure ANOVAs to compare CS and non-CS group for the 3 cortical excitability variables, respectively.