Electrical stimulation and denervated muscles after spinal cord injury

Spinal cord injury(SCI)population with injury below T10 or injury to the cauda equina region is characterized by denervated muscles,extensive muscle atrophy,infiltration of intramuscular fat and formation of fibrous tissue.These morphological changes may put individuals with SCI at higher risk for developing other diseases such as various cardiovascular diseases,diabetes,obesity and osteoporosis.Currently,there is no available rehabilitation intervention to rescue the muscles or restore muscle size in SCI individuals with lower motor neuron denervation.We,hereby,performed a review of the available evidence that supports the use of electrical stimulation in restoration of denervated muscle following SCI.Long pulse width stimulation(LPWS)technique is an upcoming method of stimulating denervated muscles.Our primary objective is to explore the best stimulation paradigms(stimulation parameters,stimulation technique and stimulation wave)to achieve restoration of the denervated muscle.Stimulation parameters,such as the pulse duration,need to be 100–1000 times longer than in innervated muscles to achieve desirable excitability and contraction.The use of electrical stimulation in animal and human models induces muscle hypertrophy.Findings in animal models indicate that electrical stimulation,with a combination of exercise and pharmacological interventions,have proven to be effective in improving various aspects like relative muscle weight,muscle cross sectional area,number of myelinated regenerated fibers,and restoring some level of muscle function.Human studies have shown similar outcomes,identifying the use of LPWS as an effective strategy in increasing muscle cross sectional area,the size of muscle fibers,and improving muscle function.Therefore,displaying promise is an effective future stimulation intervention.In summary,LPWS is a novel stimulation technique for denervated muscles in humans with SCI.Successful studies on LPWS of denervated muscles will help in translating this stimulation technique to the clinical level as a rehabilitation intervention after SCI.

MRI analysis and clinical significance of lower extremity muscle cross-sectional area after spinal cord injury

Shortly after spinal cord injury（SCI）, the musculoskeletal system undergoes detrimental changes in size and composition, predominantly below the level of injury. The loss of muscle size and strength, along with increased immobility, predisposes persons with SCI to rapid and severe loss in bone mineral density and other health related consequences. Previous studies have highlighted the significance of measuring thigh muscle cross-sectional area, however, measuring the size and composition of muscles of the lower leg may provide insights on how to decrease the risk of various comorbidities. The purpose of the current review was to summarize the methodological approach to manually trace and measure the muscles of the lower leg in individuals with SCI, using magnetic resonance imaging. We also intend to highlight the significance of analyzing lower leg muscle cross-sectional area and its relationship to musculoskeletal and vascular systems in persons with SCI.

Skeletal muscle stiffness as measured by magnetic resonance elastography after chronic spinal cord injury:a cross-sectional pilot study

Skeletal muscle stiffness is altered after spinal cord injury(SCI).Assessing muscle stiffness is essential for rehabilitation and pharmaceutical interventions design after SCI.The study used magnetic resonance elastography to assess the changes in stiffness after chronic SCI compared to matched able-bodied controls and determine its association with muscle size,spasticity,and peak torque in persons with SCI.Previous studies examined the association between muscle stiffness and spasticity,however,we are unaware of other studies that examined the effects of muscle composition on stiffness after SCI.Ten participants(one female)with chronic SCI and eight(one female)matched able-bodied controls participated in this cross-sectional study.Magnetic resonance elastography was utilized to monitor stiffness derived from shear waves propagation.Modified Ashworth scale was used to evaluate spasticity scores in a blinded fashion.Peak isometric and isokinetic torques were measured using a biodex dynamometer.Stiffness values were non-significantly lower(12.5%;P=0.3)in the SCI group compared to able-bodied controls.Moreover,stiffness was positively related to vastus lateralis whole muscle cross-sectional area(CSA)(r2=0.64,P<0.005)and vastus lateralis absolute muscle CSA after accounting for intramuscular fat(r2=0.78,P<0.0007).Stiffness was also positively correlated to both isometric(r2=0.55-0.57,P<0.05)and isokinetic peak(r2=0.46-0.48,P<0.05)torques.Our results suggest that larger clinical trial is warranted to confirm the preliminary findings that muscle stiffness is altered after SCI compared to healthy controls.Stiffness appeared to be influenced by infiltration of intramuscular fat and modestly by the spasticity of the paralyzed muscles.The preliminary data indicated that the relationship between muscle stiffness and peak torque is not altered with changing the frequency of pulses or angular velocities.All study procedures were approved by the Institutional Review Board at the Hunter Holmes McGuire VA Medical Center,USA(IRB#:02314)on May 3,2017.

Quantification of intermuscular and intramuscular adipose tissue using magnetic resonance imaging after neurodegenerative disorders

Ectopic adiposity has gained considerable attention because of its tight association with metabolic and cardiovascular health in persons with spinal cord injury（SCI）. Ectopic adiposity is characterized by the storage of adipose tissue in non-subcutaneous sites. Magnetic resonance imaging（MRI） has proven to be an effective tool in quantifying ectopic adiposity and provides the opportunity to measure different adipose depots including intermuscular adipose tissue（IMAT） and intramuscular adipose tissue（Intra MAT） or intramuscular fat（IMF）. It is highly important to distinguish and clearly define these compartments, because controversy still exists on how to accurately quantify these adipose depots. Investigators have relied on separating muscle from fat pixels based on their characteristic signal intensities. A common technique is plotting a threshold histogram that clearly separates between muscle and fat peaks. The cut-offs to separate between muscle and fat peaks are still not clearly defined and different cut-offs have been identified. This review will outline and compare the Midpoint and Otsu techniques, two methods used to determine the threshold between muscle and fat pixels on T1 weighted MRI. The process of water/fat segmentation using the Dixon method will also be outlined. We are hopeful that this review will trigger more research towards accurately quantifying ectopic adiposity due to its high relevance to cardiometabolic health after SCI.

Leisure-time physical activity,anthropometrics,and body composition as predictors of quality of life domains after spinal cord injury:an exploratory cross-sectional study

The objective of the current work was to examine the relationships between quality of life(QOL)domains in persons with spinal cord injury(SCI)and their levels of weekly leisure-time physical activity(LTPA),anthropometric variables,and body composition variables.This exploratory cross-sectional study consisted of baseline data collected as part of a randomized clinical trial at a VA Medical Center and SCI center.A convenience sample of 36 community-dwelling persons with SCI participated in the current study.Outcome measures included the World Health Organization Quality of Life Short Form(WHOQOL-BREF),Leisure-Time Physical Activity Questionnaire for People with Spinal Cord Injury(LTPAQ-SCI),anthropomorphic measures(waist,hip,and abdominal circumference),and dual-energy x-ray absorptiometry(DXA)to quantify regional and total body composition.Multiple regression models suggested that engagement in LTPA accounted for 35.7%of the variance in physical health QOL,33.5%in psychological QOL,14.2%in social relationships QOL,and 38.2%in environmental QOL.Anthropometric measures accounted for 11.3%,3.1%,12.0%,and 6.7%of the variance in these QOL indices,respectively,and DXA indices accounted for 18.7%,17.5%,27.4%,and 21.9%.Within these models,the number of minutes of heavy LTPA per day uniquely predicted physical health QOL,the number of mild LTPA days per week uniquely predicted psychological QOL,and the amount of mild LTPA per day uniquely predicted environmental QOL.Bivariate analyses also suggested that android and trunk fat,as well as supine waist and abdominal circumferences,were positively associated with social relationships QOL.Encouraging individuals with SCI to engage in LTPA may robustly enhance multiple aspects of QOL while reducing the risk for cardiovascular and metabolic morbidities associated with SCI.Moreover,this may lead to a further understanding of how QOL may impact longitudinal intervention trials.The study protocol and procedures were reviewed and approved by the McGuire VA Research Institutional Review Board(IRB#02152,approval date August 9,2015;IRB#02375,approval date May 2,2018).

Semi-automated segmentation of magnetic resonance images for thigh skeletal muscle and fat using threshold technique after spinal cord injury

Magnetic resonance imaging is considered the ＂gold standard＂ technique for quantifying thigh muscle and fat cross-sectional area. We have developed a semi-automated technique to segment seven thigh compartments in persons with spinal cord injury. Thigh magnetic resonance images from 18 men（18–50 years old） with traumatic motor-complete spinal cord injury were analyzed in a blinded fashion using the threshold technique. The cross-sectional area values acquired by thresholding were compared to the manual tracing technique. The percentage errors for thigh circumference were（threshold： 170.71 ± 38.67; manual： 169.45 ± 38.27 cm2） 0.74%, subcutaneous adipose tissue（threshold： 65.99±30.79; manual： 62.68 ± 30.22） 5.2%, whole muscle（threshold： 98.18 ± 20.19; manual： 98.20 ± 20.08 cm2） 0.13%, femoral bone（threshold： 6.53 ± 1.09; manual： 6.53 ± 1.09 cm2） 0.64%, bone marrow fat（threshold： 3.12 ± 1.12; manual： 3.1 ± 1.11 cm2） 0.36%, knee extensor（threshold： 43.98 ± 7.66; manual： 44.61 ± 7.81 cm2） 1.78% and % intramuscular fat（threshold： 10.45 ± 4.29; manual： 10.92 ± 8.35%） 0.47%. Collectively, these results suggest that the threshold technique provided a robust accuracy in measuring the seven main thigh compartments, while greatly reducing the analysis time.

Skeletal muscle conditioning may be an effective rehabilitation intervention preceding functional electrical stimulation cycling

In our recent effort,we introduced a submaximal index that utilized ventilatory efficiency relative to CO2 production（VE/CO2）to evaluate the cardiovascular effectiveness to functional electrical stimulation lower-extremity cycling（FESLEC）in persons with spinal cord injury（SCI）（Gorgey and Lawrence,2016）.

Low-dose testosterone replacement therapy and electrically evoked resistance training enhance muscle quality after spinal cord injury

The current perspective is aimed to highlight the significance of adding low-dose testosterone replacement therapy(TRT) to electrically evoked resistance training(RT).Evoked RT is primarily designed to load the paralyzed lower extremity muscles to elicit muscle hypertrophy in persons with spinal cord injury(SCI)(Ryan et al.,2013;Gorgey et al.,2019).The rationale was based on previous work that indicated that highdose TRT is likely to enhance muscle quality。

Novel rehabilitation paradigm for restoration of hand functions after tetraplegia

The letter by Bouton et al.（2016）“Restoring cortical control of functional movement in a human with quadriplegia”presents a case report of a 24 year old male with tetraplegia（C5–6）.The goal of the work was to bypass the spinal cord injury（SCI）lesion to stimulate the right forearm muscles to perform six movements and daily functional tasks.