Evoked Potentials Recorded From the Spinal Cord During Neurostimulation for Pain: A Computational Modeling Study

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153677/1/ner12965.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153677/2/ner12965_am.pd

Stratifying chronic stroke patients based on the influence of contralesional motor cortices: an inter-hemispheric inhibition study

Objective: A recent “bimodal-balance recovery” model suggests that contralesional influence varies based on the amount of ipsilesional reserve: inhibitory when there is a large reserve, but supportive when there is a low reserve. Here, we investigated the relationships between contralesional influence (inter-hemispheric inhibition, IHI) and ipsilesional reserve (corticospinal damage/impairment), and also defined a criterion separating subgroups based on the relationships. Methods: Twenty-four patients underwent assessment of IHI using Transcranial Magnetic Stimulation (ipsilateral silent period method), motor impairment using Upper Extremity Fugl-Meyer (UEFM), and corticospinal damage using Diffusion Tensor Imaging and active motor threshold. Assessments of UEFM and IHI were repeated after 5 week-rehabilitation (n=21). Results: Relationship between IHI and baseline UEFM was quadratic with criterion at UEFM 43 (95%conference interval: 40-46). Patients less impaired than UEFM=43 showed stronger IHI with more impairment, whereas patients more impaired than UEFM=43 showed lower IHI with more impairment. Of those made clinically-meaningful functional gains in rehabilitation (n=14), more-impaired patients showed further IHI reduction. Conclusions: A criterion impairment-level can be derived to stratify patient-subgroups based on the bimodal influence of contralesional cortex. Contralesional influence also evolves differently across subgroups following rehabilitation. Significance: The criterion may be used to stratify patients to design targeted, precision treatments

Triple leads programmed to perform as longitudinal guarded cathodes in spinal cord stimulation: A modeling study

Objective: In spinal cord stimulation, neurosurgeons increasingly tend to implant dual leads. Dual leads (longitudinal bipole/tripole) provide medio-lateral control over the recruited dorsal column (DC) area by steering the injected cathodal currents. However, the DC recruited area is suboptimal when dual aligned leads straddling the midline programmed as longitudinal guarded cathodes (+-+) are used instead of a single lead placed over the spinal cord midline with the same configuration. As a potential improvement, an additional third lead between the two aligned leads is modeled to maximize the medio-lateral extent of the DCs at the low-thoracic vertebral region (T10-T12). Methods and Materials: The University of Twente Spinal Cord Stimulation software (UT-SCS) is used in this modeling study. Longitudinal guarded cathodes were modeled on the low-thoracic vertebral region (T10-T12) using percutaneous triple lead configurations. The central lead was modeled over the spinal cord midline and the two lateral leads were modeled at several transverse distances to the midline lead. Medio-lateral field steering was performed with the midline lead and the second lead on each side to achieve constant anodal current ratios and variable anodal current ratios. Results: Reducing the transverse lead separation resulted in increasing the depths and widths of the recruited DC area. The triple lead configuration with the least transverse separation had the largest DC recruited area and usage range. The maximum DC recruited area (in terms of both depth and width) was always found to be larger under variable anodal current ratio than constant anodal current ratio conditions. Conclusions: Triple leads programmed to perform as longitudinal guarded cathodes provide more postoperative flexibility than single and dual leads in covering a larger width of the low-thoracic DCs. The transverse separation between the leads is a major determinant of the area and distribution of paresthesi

Staggered transverse tripoles with quadripolar lateral anodes using percutaneous and surgical leads in Spinal Cord Stimulation (SCS)

Background: In spinal cord stimulation (SCS) for low-back pain, the use of electrode arrays with both low power requirements and selective activation of target dorsal column (DC) fibers is desired. The aligned transverse tripolar lead (TTL) configuration offers the best DC selectivity. Electrode alignment of the same configuration using three parallel percutaneous leads is possible, but compromised by longitudinal migration, resulting in loss of DC selectivity. This loss might be repaired by using the adjacent anodal contacts on the lateral leads. Objective: To investigate if stimulation using adjacent anodal contacts on the lateral percutaneous leads of a staggered transverse tripole can restore DC selectivity. Methods: Staggered transverse tripoles with quadripolar lateral anodes were modeled on the low-thoracic vertebral region (T10-T12) of the spinal cord using (a) PERC QD and (b) LAM QD, of same contact dimensions. The commercial LAM 565 surgical lead with 16 widely spaced contacts was also modeled. For comparison with PERC QD, staggered transverse tripoles with dual lateral anodes were modeled using PERC ST. Results: The PERC QD improved the depth of DC penetration and enabled selective recruitment of DCs as compared to PERC ST. Medio-lateral selectivity of DCs could not be achieved with the LAM 565. Conclusion: Stimulation using PERC QD improves anodal shielding of DRs and restores DC selectivity. Based on our modeling study, we would hypothesize that, in clinical practice, LAM QD can provide an improved performance compared to the PERC QD. Our model also predicts that the same configuration realized on the commercial LAM 565 surgical lead with widely spaced contacts can not selectively stimulate DCs essential in treating low-back pain

Quantitative Sensory Testing of Spinal Cord and Dorsal Root Ganglion Stimulation in Chronic Pain Patients

Background/ObjectivesThe physiological mechanisms underlying the pain‐modulatory effects of clinical neurostimulation therapies, such as spinal cord stimulation (SCS) and dorsal root ganglion stimulation (DRGS), are only partially understood. In this pilot prospective study, we used patient‐reported outcomes (PROs) and quantitative sensory testing (QST) to investigate the physiological effects and possible mechanisms of action of SCS and DRGS therapies.Materials and MethodsWe tested 16 chronic pain patients selected for SCS and DRGS therapy, before and after treatment. PROs included pain intensity, pain‐related symptoms (e.g., pain interference, pain coping, sleep interference) and disability, and general health status. QST included assessments of vibration detection theshold (VDT), pressure pain threshold (PPT) and tolerance (PPToL), temporal summation (TS), and conditioned pain modulation (CPM), at the most painful site.ResultsFollowing treatment, all participants reported significant improvements in PROs (e.g., reduced pain intensity [p < 0.001], pain‐related functional impairment [or pain interference] and disability [p = 0.001 for both]; better pain coping [p = 0.03], sleep [p = 0.002]), and overall health [p = 0.005]). QST showed a significant treatment‐induced increase in PPT (p = 0.002) and PPToL (p = 0.011), and a significant reduction in TS (p = 0.033) at the most painful site, but showed no effects on VDT and CPM. We detected possible associations between a few QST measures and a few PROs. Notably, higher TS was associated with increased pain interference scores at pre‐treatment (r = 0.772, p = 0.009), and a reduction in TS was associated with the reduction in pain interference (r = 0.669, p = 0.034) and pain disability (r = 0.690, p = 0.027) scores with treatment.ConclusionsOur preliminary findings suggest significant clinical and therapeutic benefits associated with SCS and DRGS therapies, and the possible ability of these therapies to modulate pain processing within the central nervous system. Replication of our pilot findings in future, larger studies is necessary to characterize the physiological mechanisms of SCS and DRGS therapies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168355/1/ner13329.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168355/2/ner13329_am.pd

Transcranial direct current stimulation (tDCS) paired with massed practice training to promote adaptive plasticity and motor recovery in chronic incomplete tetraplegia: A pilot study

<p><b>Objective:</b> Our goal was to determine if pairing transcranial direct current stimulation (tDCS) with rehabilitation for two weeks could augment adaptive plasticity offered by these residual pathways to elicit longer-lasting improvements in motor function in incomplete spinal cord injury (iSCI).</p> <p><b>Design:</b> Longitudinal, randomized, controlled, double-blinded cohort study.</p> <p><b>Setting:</b> Cleveland Clinic Foundation, Cleveland, Ohio, USA.</p> <p><b>Participants:</b> Eight male subjects with chronic incomplete motor tetraplegia.</p> <p><b>Interventions:</b> Massed practice (MP) training with or without tDCS for 2 hrs, 5 times a week.</p> <p><b>Outcome Measures:</b> We assessed neurophysiologic and functional outcomes before, after and three months following intervention. Neurophysiologic measures were collected with transcranial magnetic stimulation (TMS). TMS measures included excitability, representational volume, area and distribution of a weaker and stronger muscle motor map. Functional assessments included a manual muscle test (MMT), upper extremity motor score (UEMS), action research arm test (ARAT) and nine hole peg test (NHPT).</p> <p><b>Results:</b> We observed that subjects receiving training paired with tDCS had more increased strength of weak proximal (15% vs 10%), wrist (22% vs 10%) and hand (39% vs. 16%) muscles immediately and three months after intervention compared to the sham group. Our observed changes in muscle strength were related to decreases in strong muscle map volume (r=0.851), reduced weak muscle excitability (r=0.808), a more focused weak muscle motor map (r=0.675) and movement of weak muscle motor map (r=0.935).</p> <p><b>Conclusion:</b> Overall, our results encourage the establishment of larger clinical trials to confirm the potential benefit of pairing tDCS with training to improve the effectiveness of rehabilitation interventions for individuals with SCI.</p> <p><b>Trial Registration:</b> NCT01539109</p