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Background: Painful diabetic neuropathy (pDN) is the most common cause of neuropathic pain (NP) in the United States. Prolonged continuous theta burst stimulation (pcTBS), a form of repetitive transcranial magnetic stimulation (rTMS), is quick (1-4 minutes) and tolerable for most individuals, compared to high frequency rTMS and can modulate pain thresholds in healthy participants. However, its effects on patients with chronic pain are still unclear. The primary purpose of this preliminary study is to investigate the effects of single session pcTBS targeted at the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) on a set of self-report measures of pain (SRMP) that assess the (a) sensory-discriminative; (b) affective-motivational; and (c) cognitive-evaluative aspects of pain experience. Methods: For this prospective, single-blind study, forty-two participants with pDN were randomized to receive either pcTBS targeting the M1 or the DLPFC brain regions. SRMP were completed at baseline, post pcTBS and 24h-post pcTBS. A two-way mixed model repeated measures analysis of variance (2 brain regions by 3 time points) was conducted to evaluate the effects of pcTBS stimulation at M1 and DLPFC for each subscale of each SRMP. Results: After a single session of pcTBS targeted at M1 or DLPFC in patients with pDN, statistically significant improvements from baseline to post pcTBS and baseline to 24 h-post pcTBS were observed for different SRMP subscales examining the (a) sensory-discriminative, (b) affective-motivational and (c) cognitive-evaluative components of the pain experience. At 24 h-post pcTBS, none of the participants reported any serious adverse events to the pcTBS treatment, thus demonstrating its feasibility. Conclusions: In pDN patients with NP, our study results demonstrated significant improvement in scores on self-report measures of pain (SRMP) after a single session of pcTBS targeting the M1 and DLPFC brain regions. Future studies should consider utilizing multiple sessions of pcTBS to evaluate its long-term effects on pain perception, safety and tolerability in patients with chronic pain. Clinical Trial Registration: This study was registered on the ClinicalTrials.gov website (NCT04988321). [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique used in the treatment of several neurological conditions. The dosage parameter for TMS protocols is the resting motor threshold (RMT) which has been shown to vary between participants with limited understanding. The goal of this study was to investigate how white matter-derived fiber tracts integrated into finite element analysis simulations influence TMS response in the form of RMT. Ten healthy participants were included in this study who underwent TMS, diffusion tensor imaging, and structural magnetic resonance imaging. Anatomically accurate head models were created, and fiber tracts were extracted from Diffusion tensor imaging and integrated into these head models before finite element analysis simulations were performed to model the effects of empirical TMS. Linear mixed effects models were used to evaluate how the induced electric field strength on the fiber tracts (EFSTract) influenced RMT. We found the induced electric field strength along fiber tracts did influence RMT, however the effect of this relationship on RMT is not clinically relevant due to its small magnitude. This suggests finite element analysis of the fiber tracts is not meaningful when tracts are considered a homogenous material and thus lacking physiology. However, tractography provides a valuable framework within which to organize physiological models of signal transmission, and it is likely a combination of this approach with more physiologically detailed modeling would provide more accurate RMT prediction. [ABSTRACT FROM AUTHOR]

Following tendon transfer of the biceps to triceps after cervical spinal cord injuries (SCI), individuals must learn to activate the transferred biceps muscle to extend the elbow. Corticomotor excitability of the transferred biceps may play a role in post-operative elbow extension strength. In this study, we evaluated whether corticomotor excitability of the transferred biceps is related to an individuals' ability to extend the elbow, and whether posture and muscle length affects corticomotor excitability after SCI and tendon transfer similarly to the nonimpaired biceps. Corticomotor excitability was assessed in twelve nonimpaired arms and six arms of individuals with SCI and biceps-to-triceps transfer using transcranial magnetic stimulation (TMS) delivered at rest. Maximum isometric elbow extensor moments were recorded in transferred arms and the fiber length of the transferred biceps was estimated using a musculoskeletal model. Across the SCI subjects, corticomotor excitability of the transferred biceps increased with elbow extension strength. Thus, rehabilitation to increase excitability may enhance strength. Excitability of the transferred biceps was not related to fiber length suggesting that similar to nonimpaired subjects, posture-dependent changes in biceps excitability are primarily centrally modulated after SCI. All nonimpaired biceps were most excitable in a posture in the horizontal plane with the forearm fully supinated. The proportion of transferred biceps in which excitability was highest in this posture differed from the nonimpaired group. Therefore, rehabilitation after tendon transfer may be most beneficial if training postures are tailored to account for changes in biceps excitability.