Proceedings #52: Development of surface EMG- triggered closed loop stimulation for individuals with spinal cord injury

Closed-loop vagus nerve stimulation (VNS) paired with rehabilitative training has emerged as a strategy to enhance recovery after neurological injury. Previous studies demonstrate that brief bursts of closed-loop VNS paired with rehabilitative training substantially improve recovery of forelimb motor function in models of unilateral and bilateral contusive spinal cord injury (SCI) at spinal level C5/6. While these findings provide initial evidence of the utility of VNS for SCI, the injury model used in these studies spares the majority of alpha motor neurons originating in C7-T1 that innervate distal forelimb muscles. Because the clinical manifestation of SCI in many patients involves damage at these levels, it is important to define whether damage to the distal forelimb motor neuron pools limits VNS-dependent recovery. In this study, we assessed recovery of forelimb function in rats that received a bilateral incomplete contusive SCI at C7/8 and underwent extensive rehabilitative training with or without paired VNS. The study design, including planned sample size, assessments, and statistical comparisons, was preregistered prior to beginning data collection ( https://osf.io/ysvgf/ ). VNS paired with rehabilitative training significantly improved recovery of volitional forelimb strength compared to equivalent rehabilitative training without VNS. Additionally, VNS-dependent enhancement of recovery generalized to 2 similar, but untrained, forelimb tasks. These findings indicate that damage to alpha motor neurons does not prevent VNS-dependent enhancement of recovery and provides additional evidence to support the evaluation of closed-loop VNS paired with rehabilitation in patients with incomplete cervical SCI.

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Characterization of Volitional Electromyographic Signals in the Lower Extremity After Motor Complete Spinal Cord Injury

Neurorehabilitation and Neural Repair ◽

10.1177/1545968317704904 ◽

2017 ◽

Vol 31 (6) ◽

pp. 583-591 ◽

Cited By ~ 11

Author(s):

Elizabeth Heald ◽

Ronald Hart ◽

Kevin Kilgore ◽

P. Hunter Peckham

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Lower Extremity ◽

Visual Inspection ◽

Surface Emg ◽

Emg Activity ◽

Automatic Identification ◽

Emg Signal ◽

Cord Injury ◽

Complete Spinal Cord Injury

Background. Previous studies have demonstrated the presence of intact axons across a spinal cord lesion, even in those clinically diagnosed with complete spinal cord injury (SCI). These axons may allow volitional motor signals to be transmitted through the injury, even in the absence of visible muscle contraction. Objective. To demonstrate the presence of volitional electromyographic (EMG) activity below the lesion in motor complete SCI and to characterize this activity to determine its value for potential use as a neuroprosthetic command source. Methods. Twenty-four subjects with complete (AIS A or B), chronic, cervical SCI were tested for the presence of volitional below-injury EMG activity. Surface electrodes recorded from 8 to 12 locations of each lower limb, while participants were asked to attempt specific movements of the lower extremity in response to visual and audio cues. EMG trials were ranked through visual inspection, and were scored using an amplitude threshold algorithm to identify channels of interest with volitional motor unit activity. Results. Significant below-injury muscle activity was identified through visual inspection in 16 of 24 participants, and visual inspection rankings were well correlated to the algorithm scoring. Conclusions. The surface EMG protocol utilized here is relatively simple and noninvasive, ideal for a clinical screening tool. The majority of subjects tested were able to produce a volitional EMG signal below their injury level, and the algorithm developed allows automatic identification of signals of interest. The presence of this volitional activity in the lower extremity could provide an innovative new command signal source for implanted neuroprostheses or other assistive technology.

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A Comparison of Closed-Loop Control Algorithms for Regulating Electrically Stimulated Knee Movements in Individuals With Spinal Cord Injury

IEEE Transactions on Neural Systems and Rehabilitation Engineering ◽

10.1109/tnsre.2012.2185065 ◽

2012 ◽

Vol 20 (4) ◽

pp. 539-548 ◽

Cited By ~ 47

Author(s):

C. L. Lynch ◽

M. R. Popovic

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Closed Loop ◽

Control Algorithms ◽

Closed Loop Control ◽

Loop Control ◽

Cord Injury

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Gait Initiation With Electromyographically Triggered Electrical Stimulation in People With Partial Paralysis

Journal of Biomechanical Engineering ◽

10.1115/1.3086356 ◽

2009 ◽

Vol 131 (8) ◽

Cited By ~ 25

Author(s):

Anirban Dutta ◽

Rudi Kobetic ◽

Ronald J. Triolo

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Electrical Stimulation ◽

Normative Data ◽

Surface Emg ◽

Gait Initiation ◽

Incomplete Spinal Cord Injury ◽

Volitional Control ◽

Fixed Rate ◽

Cord Injury

Functional electrical stimulation (FES) facilitates ambulatory function after paralysis by activating the muscles of the lower extremities. Individuals with incomplete spinal cord injury (iSCI) retain partial volitional control of muscles below the level of injury, necessitating careful integration of FES with intact voluntary motor function for efficient walking. The FES-assisted stepping can be triggered automatically at a fixed rate (autotrigger), by a manual switch (switch-trigger), or by an electromyogram-based gait-event-detector (EMG-trigger). It has been postulated that EMG may be a more natural command source than manual switches, and therefore will enable better coordination of stimulated and volitional motor functions necessary during gait. In this study, the above stated hypothesis was investigated in two volunteers with iSCI during the over-ground FES-assisted gait initiation. Four able-bodied volunteers provided the normative data for comparison. The EMG-triggered FES-assisted gait initiation was found to be more coordinated and dynamically more stable than autotriggered and switch-triggered cases. This highlighted the potential of surface EMG as a natural command interface to better coordinate stimulated and volitional muscle activities during gait.

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Restoration of motor function following spinal cord injury via optimal control of intraspinal microstimulation: toward a next generation closed-loop neural prosthesis

Frontiers in Neuroscience ◽

10.3389/fnins.2014.00296 ◽

2014 ◽

Vol 8 ◽

Cited By ~ 23

Author(s):

Peter J. Grahn ◽

Grant W. Mallory ◽

B. Michael Berry ◽

Jan T. Hachmann ◽

Darlene A. Lobel ◽

...

Keyword(s):

Spinal Cord ◽

Optimal Control ◽

Spinal Cord Injury ◽

Motor Function ◽

Closed Loop ◽

Neural Prosthesis ◽

Next Generation ◽

Intraspinal Microstimulation ◽

Cord Injury

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Quantitative and sensitive assessment of neurophysiological status after human spinal cord injury

Journal of Neurosurgery Spine ◽

10.3171/2012.6.aospine12117 ◽

2012 ◽

Vol 17 (Suppl1) ◽

pp. 77-86 ◽

Cited By ~ 12

Author(s):

Kun Li ◽

Darryn Atkinson ◽

Maxwell Boakye ◽

Carie Z. Tolfo ◽

Sevda Aslan ◽

...

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Motor Function ◽

Surface Emg ◽

Emg Activity ◽

Motor Score ◽

Emg Signal ◽

Cord Injury ◽

Kendall Correlation ◽

Lesion Severity

Object This study was designed to develop an objective and sensitive spinal cord injury (SCI) characterization protocol based on surface electromyography (EMG) activity. Methods Twenty-four patients at both acute and chronic time points post-SCI, as well as 4 noninjured volunteers, were assessed using neurophysiological and clinical measures of volitional motor function. The EMG amplitude was recorded from 15 representative muscles bilaterally during standardized maneuvers as a neurophysiological assessment of voluntary motor function. International Standards for the Neurological Classification of Spinal Cord Injury (ISNCSCI) examinations were performed as a clinical assessment of lesion severity. Results Sixty-six functional neurophysiological assessments were performed in 24 patients with SCI and in 4 neurologically intact individuals. The collected EMG data were organized by quantitative parameters and statistically analyzed. The correlation between root mean square (RMS) of the EMG signals and ISNCSCI motor score was confirmed by Kendall correlation analysis. The Kendall correlation value between overall muscles/levels, motor scores, and the RMS of the EMG data is 0.85, with the 95% CI falling into the range of 0.76–0.95. Significant correlations were also observed for the soleus (0.51 [0.28–0.74]), tibialis anterior (TA) (0.53 [0.33–0.73]), tricep (0.52, [0.34–0.70]), and extensor carpi radialis (ECR) (0.80 [0.42–1.00]) muscles. Comparisons of RMS EMG values in groups defined by ISNCSCI motor score further confirmed these results. At the bicep and ECR, patients with motor scores of 5 had nearly significantly higher RMS EMG values than patients with motor scores of 0 (p = 0.059 and 0.052, respectively). At the soleus and TA, the RMS of the EMG value was significantly higher (p < 0.01) for patients with American Spinal Injury Association Impairment Scale motor scores of 5 than for those with ISNCSCI motor scores of 0. Those with C-7 ISNCSCI motor scores of 5 had significantly higher RMS EMG values at the tricep than those with motor scores of 4 (p = 0.008) and 0 (p = 0.02). Results also show that surface EMG signals recorded from trunk muscles allowed the examiner to pick up subclinical changes, even though no ISNCSCI scores were given. Conclusions Surface EMG signal is suitable for objective neurological SCI characterization protocol design. The quantifiable features of surface EMG may increase SCI characterization resolution by adding subclinical details to the clinical picture of lesion severity and distribution.

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