Mechanical and neural changes in plantar-flexor muscles after spinal cord injury in humans

Muscle Atrophy Evaluation via Radiomics Analysis using Ultrasound Images: A Cohort Data Study

OBJECTIVE

Existing methods for muscle atrophy evaluation based on muscle size measures from ultrasound images are inadequate in precision. Radiomics has been widely used in various medical studies, but its validity for the evaluation of muscle atrophy has not been fully explored.

METHODS

This study presents a radiomics analysis for muscle atrophy evaluation using ultrasound images. The hindlimb unloading rat model was developed to simulate weightlessness muscle atrophy and ultrasound images of the hind limbs were acquired for both the hindlimb unloaded (HU) and control groups during a 21-day HU period. A total of 368 radiomics features were extracted and the stable and informative features were selected through a two-stage feature selection procedure. The feature change trajectory of the stable features was analyzed using the hierarchical clustering method. Finally, an adaptive longitudinal feature selection and grading network, ALNet, was developed to evaluate muscle atrophy.

RESULTS

The clustering trajectories of ultrasound image features showed similar trends to the changes in muscle atrophy at the molecular level. The best grading accuracy achieved by the ALNet was 79.5% for the Soleus (Sol) muscle and 82.6% for the Gastrocnemius (Gas) muscle.

CONCLUSION

The test-retest is essential in performing radiomics analysis on ultrasound images. The longitudinal feature selection is important for muscle atrophy grading. The ultrasound image features of the Gas muscle have better discrimination ability than that of the Sol muscle. This study proves for the first time the capability of ultrasound image features for muscle atrophy evaluation.

Bilateral and asymmetrical contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with spinal cord injury

Spasticity is one of the most common symptoms present in humans with spinal cord injury (SCI); however, its clinical assessment remains underdeveloped. The purpose of the study was to examine the contribution of passive muscle stiffness and active spinal reflex mechanisms to clinical outcomes of spasticity after SCI. It is important that passive and active contributions to increased muscle stiffness are distinguished to make appropriate decisions about antispastic treatments and to monitor its effectiveness. To address this question, we combined biomechanical and electrophysiological assessments of ankle plantarflexor muscles bilaterally in individuals with and without chronic SCI. Spasticity was assessed using the Modified Ashworth Scale (MAS) and a self-reported questionnaire. We performed slow and fast dorsiflexion stretches of the ankle joint to measure passive muscle stiffness and reflex-induced torque using a dynamometer and the soleus H reflex using electrical stimulation over the posterior tibial nerve. All SCI participants reported the presence of spasticity. While 96% of them reported higher spasticity on one side compared with the other, the MAS detected differences across sides in only 25% of the them. Passive muscle stiffness and the reflex-induced torque were larger in SCI compared with controls more on one side compared with the other. The soleus stretch reflex, but not the H reflex, was larger in SCI compared with controls and showed differences across sides, with a larger reflex in the side showing a higher reflex-induced torque. MAS scores were not correlated with biomechanical and electrophysiological outcomes. These findings provide evidence for bilateral and asymmetric contributions of passive and active ankle plantar flexors stiffness to spasticity in humans with chronic SCI and highlight a poor agreement between a self-reported questionnaire and the MAS for detecting asymmetries in spasticity across sides.NEW & NOTEWORTHY Spasticity affects a number of people with spinal cord injury (SCI). Using biomechanical, electrophysiological, and clinical assessments, we found that passive muscle properties and active spinal reflex mechanisms contribute bilaterally and asymmetrically to spasticity in ankle plantarflexor muscles in humans with chronic SCI. A self-reported questionnaire had poor agreement with the Modified Ashworth Scale in detecting asymmetries in spasticity. The nature of these changes might contribute to the poor sensitivity of clinical exams.

Fatigue in complete spinal cord injury and implications on total delay

The use of neuromuscular electrical stimulation (NMES) to artificially restore movement in people with complete spinal cord injury (SCI) induces an accelerated process of muscle fatigue. Fatigue increases the time between the beginning of NMES and the onset of muscle force (Delay_TOT ). Understanding how much muscle fatigue affects the Delay_TOT in people with SCI could help in the design of closed-loop neuroprostheses that compensate for this delay, thus making the control system more stable. The aim of this study was to evaluate the impact of the extent of fatigue on Delay_TOT and peak force of the lower limbs in people with complete SCI. Fifteen men-young adults with complete SCI (paraplegia and tetraplegia) and stable health-participated in the experiment. Delay_TOT was defined as the time interval between the beginning of NMES application until the onset of muscle force. The electrical intensity of NMES applied was adjusted individually and consisted of the amplitude required to obtain a full extension of the knee (0°), considering the maximum electrically stimulated extension (MESE). Subsequently, 70% of the MESE was applied during the fatigue induction protocol. Significant differences were identified between the moments before and after the fatigue protocol, both for peak force (P ≤ .026) and Delay_TOT (P ≤ .001). The medians and interquartile range of the Delay_TOT were higher in postfatigue (199.0 ms) when compared to the moment before fatigue (146.5 ms). The medians and interquartile range of the peak force were higher in unfatigued lower limbs (0.43 kgf) when compared to the moment postfatigue (0.27 kgf). The results support the hypothesis that muscle fatigue influences the increase in Delay_TOT and decrease in force production in people with SCI. For future applications, the combined evaluation of the delay and force in SCI patients provides valuable feedback for NMES paradigms. The study will provide potentially critical muscle mechanical evidence for the investigation of the evolution of atrophy.

Lower extremity muscle structure in incomplete spinal cord injury: a comparison between ultrasonography and magnetic resonance imaging

INTRODUCTION

Ultrasound (US) measures of muscle thickness are used in the management and monitoring of muscle changes during rehabilitation, but it is unknown how this measure compares to magnetic resonance imaging (MRI) measures of muscle cross-sectional area (CSA) in patients with spinal cord injury (SCI).

CASE PRESENTATION

Six participants with incomplete SCI underwent US imaging and MRI of their gastrocnemius and tibialis anterior (TA) muscles.

DISCUSSION

Significant correlations were found between US muscle thickness and MRI CSA in the gastrocnemius (R=0.91, P<0.001), and TA muscles (R=0.58, P<0.05). US muscle thickness in the gastrocnemius and TA of patients with incomplete SCI may be used as a cheaper alternative measure of CSA as measured using MRI, and this measure may be clinically useful to track progress in muscle gains during rehabilitation.

Epidemiological study of traumatic spinal cord injuries: experience from a specialized spine center in Iran

STUDY DESIGN

A cross-sectional study.

OBJECTIVES

This study was performed for epidemiological assessment of Iranian Traumatic Spinal Cord Injuries (TSCI), referred to a specialized spine center.

SETTING

Patient recruitment and evaluations were conducted at the Brain and Spinal Injury Research Center, Tehran, Iran.

METHODS

This study was performed from September 2011 to March 2015 on 1137 consecutive TSCIs. History, clinicoradiological findings as well as chronic complications and social integration were recorded. The capture-recapture method was used to calculate a rough estimation of TSCI prevalence in Tehran Province.

RESULTS

Our report includes 1137 cases with a mean age of 29.1 years (s.d.=11.2 year)-79.2% of them being male (M/F=3.8/1). Rough estimation of TSCI prevalence in Tehran province was 2.36 per 10 000 population. Regarding etiology, 61.8% were due to motor vehicle accident (MVA), followed by falling 24.5%, heavy drop 5.2%, violence 3.8%, sport 2.8% and others causes 1.9%. Regarding injury level, 31.5% were cervical, 57.9% thoracic and 10.6% lumbar. Complete lesions were 53.5% of patients and 46.5% were incomplete. Most common neurological type was T1-S5 (American Spinal Injury Association Impairment Scale: A, B, C, 61.7%). Most common complications included urinary tract infection followed by pressure sore (grade III and IV, 37.5%), autonomic dysreflexia (37%) and neuropathic pain (31.2%). Substance abuse was observed in 8.8% of cases. Overall, ~25% in our cases were employed after TSCI. Secondary divorce was also much more frequent than normal matched controls.

CONCLUSION

MVA was the most common cause for TSCI. The elderly subjects were less frequent among our patients than more developed countries. The high rate of unemployment and divorce in our cases deserves special consideration.