Pathophysiology of Neuromuscular Respiratory Diseases

Trunk muscle dysfunction in patients with myotonic dystrophy type 2 and its contribution to chronic low back pain

Introduction

Myotonic dystrophy type 2 (MD2) presents with a varied manifestation. Even though the myopathy in these patients is more widespread, axial musculature involvement is one of the most prominent conditions. MD2 patients also often report chronic low back pain (CLBP). The purpose of this study was to evaluate trunk muscle function, including respiratory muscles, in patients with MD2 and to compare it with healthy controls, to determine the occurrence of CLBP in patients with MD2, and to assess whether trunk muscle dysfunction increases the risk of CLBP in these patients.

Methods

We enrolled 40 MD2 patients (age range 23 to 76 years, 26 women). A comprehensive battery of tests was used to evaluate trunk muscle function. The tests consisted of quantitative muscle strength testing of low back extensor muscles and respiratory muscles and the assessment of trunk muscle endurance. A neurological evaluation contained procedures assessing the distribution of muscle weakness, myotonia, and pain, and used questionnaires focused on these items and on disability, depression, and physical activity.

Results

The results of this study suggest that patients with MD2 show significant dysfunction of the trunk muscles, including the respiratory muscles, expressed by decreased muscle strength and endurance. The prevalence of CLBP in patients with MD2 was 52.5%. Based on our analysis, the only independent significant risk factor for CLBP in these patients was maximal isometric lower back extensor strength in a prone position ≤ 15.8 kg (OR = 37.3). Other possible risk factors were severity of myotonia and reduced physical activity.

Conclusion

Outcomes of this study highlighted the presence of axial muscle dysfunction, respiratory muscle weakness, and frequent occurrence of CLBP together with its risk factors in patients with MD2. We believe that the findings of this study may help in management and prevention programs for patients with MD2.

Current Update on Role of Hesperidin in Inflammatory Lung Diseases: Chemistry, Pharmacology, and Drug Delivery Approaches

Inflammation is a common feature of many respiratory diseases, such as pneumonia, asthma, pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), lung cancer, acute lung injury, and COVID-19. Flavonoids have demonstrated their anti-inflammatory and antioxidant effects by influencing inflammation at different stages and majorly impacting several respiratory diseases’ onset and development. According to current studies, hesperidin, one of the most abundant polyphenols, can inhibit transcription factors or regulatory enzymes essential for controlling inflammation-linked mediators, including nuclear factor-kappa B (NF-κB), Inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). It also improved cellular antioxidant defences by activating the ERK/Nrf2 signalling pathway. Therefore, this review provides the latest studies on the effect of hesperidin in different respiratory diseases, its pharmacokinetic profile, and innovative drug delivery methods.

Spirometry correlates with physical activity in patients with Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is associated with progressive muscle weakness and respiratory decline. To date, studies have focused on respiratory decline and loss of ambulation as a metric of loss of skeletal muscle strength. However, new functional measures can assess skeletal muscle disease regardless of ambulatory status. The relationship between these tests and concurrent lung function is currently unexplored.

OBJECTIVE

To assess the correlation between spirometry measurements and functional muscle assessments such as accelerometry and quantitative muscle testing (QMT).

METHODS

Enrolled patients with DMD underwent accelerometry and QMT at study clinic visits. Any pulmonary function testing within 6 months of visit was obtained from the electronic medical record. The Spearman correlation coefficient was used to assess the relationship between spirometry and functional muscle testing.

RESULTS

Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1 ) demonstrated the strongest correlation with accelerometry. Both FVC and FEV1 showed a similar relationship to accelerometry when activity was divided into intensity categories, with low intensity and moderate-to-vigorous activity categories showing the strongest correlation. Maximal expiratory pressure (MEP) and FVC showed the most robust correlations with total QMT (p < 0.001 and p < 0.01, respectively).

CONCLUSION

Lung function, specifically FVC percent predicted and FEV1 %p, shows a good correlation with upper and lower extremity skeletal muscle functional testing such as accelerometry and QMT.

Chronic Neuromuscular Respiratory Failure and Home Assisted Ventilation

Chronic respiratory failure is a common, important complication of many types of neuromuscular and chest wall disorders. While the pathophysiology of each disease may be different, these disorders can variably affect all muscles involved in breathing, including inspiratory, expiratory, and bulbar muscles, ultimately leading to chronic respiratory failure and hypoventilation. The use of home assisted ventilation through noninvasive interfaces aims to improve the symptoms of hypoventilation, improve sleep quality, and, when possible, improve mortality. An increasing variety of interfaces has allowed for improved comfort and compliance. In a minority of scenarios, noninvasive ventilation is either not appropriate or no longer effective due to disease progression, and a transition to tracheal ventilation should be considered.

Two-dimensional shear wave elastography: a new tool for evaluating respiratory muscle stiffness in chronic obstructive pulmonary disease patients

BACKGROUND

Impaired respiratory function caused by respiratory muscle dysfunction is one of the common consequences of chronic obstructive pulmonary disease (COPD). In this study, two-dimensional shear wave elastography (2D-SWE) was used to measure diaphragm stiffness (DS) and intercostal muscle stiffness (IMS) in patients with COPD; in addition, the value of 2D-SWE in evaluating respiratory function was determined.

METHODS

In total, 219 consecutive patients with COPD and 20 healthy adults were included. 2D-SWE was used to measure the DS and IMS, and lung function was also measured. The correlation between respiratory muscle stiffness and lung function and the differences in respiratory muscle stiffness in COPD patients with different severities were analysed.

RESULTS

2D-SWE measurements of the DS and IMS presented with high repeatability and consistency, with ICCs of 0.756 and 0.876, respectively, and average differences between physicians of 0.10 ± 1.61 and 0.07 ± 1.65, respectively. In patients with COPD, the DS and IMS increased with disease severity (F₁ = 224.50, F₂ = 84.63, P < 0.001). In patients with COPD, the correlation with the forced expiratory volume in one second (FEV₁)/forced vital capacity (FVC), predicted FEV₁% value, residual volume (RV), total lung capacity (TLC), RV/TLC, functional residual capacity (FRC) and inspiratory capacity (IC) of DS (r₁=-0.81, r₂=-0.63, r₃ = 0.65, r₄ = 0.54, r₅ = 0.60, r₆ = 0.72 and r₇=-0.41, respectively; P < 0.001) was stronger than that of IMS (r₁=-0.76, r₂=-0.57, r₃ = 0.57, r₄ = 0.47, r₅ = 0.48, r₆ = 0.60 and r₇=-0.33, respectively; P < 0.001).

CONCLUSION

2D-SWE has potential for use in evaluating DS and IMS. A specific correlation was observed between respiratory muscle stiffness and lung function. With the worsening of the severity of COPD and the progression of lung function impairment, the DS and IMS gradually increased.

Assessment of Lumbar Extensor Muscles in the Context of Trunk Function, a Pilot Study in Healthy Individuals

A comprehensive assessment of trunk function, including the lumbar extensor muscles, appears to be important in various conditions affecting axial musculature. This pilot cross-sectional observational study aimed to define a battery of tests that comprehensively assess trunk muscle function (strength and muscular endurance). Sixty subjects without low back pain (LBP) underwent measurement of isometric lower back extensor strength using a hand-held dynamometer (HHD) in three positions; measurement of respiratory muscle strength; and Biering-Sørensen, prone-plank, and side-bridge tests. The repeatability, short-term and long-term reliability using the HHD device in different postural positions was confirmed. The greatest isometric lower back extensor strength was generated in the sitting position by male subjects. Time of effort in the Biering-Sørensen test was longer in women and older subgroups than in men and younger individuals, although this was not the case for the other two muscular endurance tests. This pilot monitoring of trunk muscle strength and endurance in healthy volunteers may lead to a better understanding of trunk muscle function. Based on this methodological background, the authors aim to use the defined battery of tests in their further studies in a group of patients with LBP and certain neuromuscular diseases to verify its usefulness in clinical practice.

Respiratory Complications of Pediatric Neuromuscular Diseases

Respiration is an event of oxygen consumption and carbon dioxide production. Respiratory failure is common in pediatric neuromuscular diseases and the main cause of morbidity and mortality. It is a consequence of lung failure, ventilatory pump failure, or their combination. Lung failure often is due to chronic aspiration either from above or from below. It may lead to end-stage lung disease. Ventilatory pump failure is caused by increased respiratory load and progressive respiratory muscles weakness. This article reviews the normal function of the respiratory pump, general pathophysiology issues, abnormalities in the more common neuromuscular conditions and noninvasive interventions.

Neurophysiological Changes in the First Year After Cell Transplantation in Sub-acute Complete Paraplegia

Neurophysiological testing can provide quantitative information about motor, sensory, and autonomic system connectivity following spinal cord injury (SCI). The clinical examination may be insufficiently sensitive and specific to reveal evolving changes in neural circuits after severe injury. Neurophysiologic data may provide otherwise imperceptible circuit information that has rarely been acquired in biologics clinical trials in SCI. We reported a Phase 1 study of autologous purified Schwann cell suspension transplantation into the injury epicenter of participants with complete subacute thoracic SCI, observing no clinical improvements. Here, we report longitudinal electrophysiological assessments conducted during the trial. Six participants underwent neurophysiology screening pre-transplantation with three post-transplantation neurophysiological assessments, focused on the thoracoabdominal region and lower limbs, including MEPs, SSEPs, voluntarily triggered EMG, and changes in GSR. We found several notable signals not detectable by clinical exam. In all six participants, thoracoabdominal motor connectivity was detected below the clinically assigned neurological level defined by sensory preservation. Additionally, small voluntary activations of leg and foot muscles or positive lower extremity MEPs were detected in all participants. Voluntary EMG was most sensitive to detect leg motor function. The recorded MEP amplitudes and latencies indicated a more caudal thoracic level above which amplitude recovery over time was observed. In contrast, further below, amplitudes showed less improvement, and latencies were increased. Intercostal spasms observed with EMG may also indicate this thoracic “motor level.” Galvanic skin testing revealed autonomic dysfunction in the hands above the injury levels. As an open-label study, we can establish no clear link between these observations and cell transplantation. This neurophysiological characterization may be of value to detect therapeutic effects in future controlled studies.

Diaphragm ultrasonography and pulmonary function tests in patients with spinal cord injury

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To investigate the role of ultrasonographic measurement of the diaphragm thickness on pulmonary function tests in patients with spinal cord injury (SCI).

SETTING

Rehabilitation center in Ankara, Turkey.

METHODS

A total of 42 patients (34 M, 8 F) with SCI and 20 able-bodied volunteers (8 M, 12 F) were enrolled. Patients with SCI were divided into three groups according to their neurological (injury) levels. All participants underwent ultrasonographic measurements for diaphragm thickness on both sides and spirometric tests for pulmonary functions. The thickness ratio of the diaphragm was also calculated.

RESULTS

There were seven patients (5 M, 2 F) in C2-C4 injury group, 14 patients (12 M, 2 F) in C5-T5 group, 21 patients (14 M, 7 F) in T6-L2 group, and 20 able-bodied volunteers (8 M, 12 F). The diaphragms of C2-C4 group were thicker than those of the controls at end-inspirium on the right side (2.7 ± 0.7 mm vs. 2.0 ± 0.5 mm; p = 0.035). The thickness ratios of C2-C4 group were lower than those of controls on the right (0.8 ± 0.4 vs. 1.5 ± 0.5; p = 0.005) and left (0.8 ± 0.5 vs. 1.6 ± 0.7; p = 0.003) sides. For all the pulmonary function tests (except for FEV1/FVC); patients with SCI had worse results than controls; and among the SCI groups, the higher the injury level, the worse the results.

CONCLUSION

Although patients with high-level SCI had worse pulmonary function tests and decreased the contractile capacity of the diaphragm, they had thicker diaphragm muscles than controls. This may have been due to the compensatory effect of the diaphragm (performing its maximum contraction capacity and increasing frequency of inspiration).