Characterization of Gait and Postural Regulation in Late-Onset Pompe Disease

Degeneration of muscle spindles in a murine model of Pompe disease

Pompe disease is a debilitating medical condition caused by a functional deficiency of lysosomal acid alpha-glucosidase (GAA). In addition to muscle weakness, people living with Pompe disease experience motor coordination deficits including an instable gait and posture. We reasoned that an impaired muscle spindle function might contribute to these deficiencies and therefore analyzed proprioception as well as muscle spindle structure and function in 4- and 8-month-old Gaa-/- mice. Gait analyses showed a reduced inter-limb and inter-paw coordination in Gaa-/- mice. Electrophysiological analyses of single-unit muscle spindle proprioceptive afferents revealed an impaired sensitivity of the dynamic and static component of the stretch response. Finally, a progressive degeneration of the sensory neuron and of the intrafusal fibers was detectable in Gaa-/- mice. We observed an increased abundance and size of lysosomes, a fragmentation of the inner and outer connective tissue capsule and a buildup of autophagic vacuoles in muscle spindles from 8-month-old Gaa-/- mice, indicating lysosomal defects and an impaired autophagocytosis. These results demonstrate a structural and functional degeneration of muscle spindles and an altered motor coordination in Gaa-/- mice. Similar changes could contribute to the impaired motor coordination in patients living with Pompe disease.

Motor Function Characteristics of Adults With Late-Onset Pompe Disease: A Systematic Scoping Review

BACKGROUND AND OBJECTIVES

Pompe disease is a rare neuromuscular disease caused by a deficiency of the lysosomal enzyme acid α-glucosidase. The late-onset Pompe disease (LOPD) in adults is characterized by weakness of ventilatory, axial, and proximal extremity muscles. These muscle impairments progressively impair various motor functions such as locomotion and postural control. Nearly 87% of adults with LOPD (aLOPD) report walking problems, and more than 80% report instability and falls. Knowledge of these motor functions is now sufficient to provide a clear and comprehensive overview of motor function in aLOPD. Therefore, this scoping review aimed to summarize current knowledge about motor function in aLOPD. It specifically targeted neuromuscular performance, locomotion, and postural control.

METHODS

A systematic search in MEDLINE (through PubMed), EMBASE, and Cochrane databases was conducted until May 2021. We included studies providing primary data on at least 4 participants, exploring neuromuscular performance, locomotion, and/or postural control in aLOPD. Risk of bias analysis was assessed using tools appropriate to the study designs; the risk of bias 2 (Cochrane tool) for randomized controlled trials, risk of bias in Nonrandomized Studies - of Interventions (Cochrane tool) for nonrandomized interventional trials, and the Newcastle-Ottawa Scale for cohort studies and case-control studies.

RESULTS

The search identified 2,885 articles. After screening, 58 articles were included in the analysis. In these studies, 88% explored locomotion, 83% neuromuscular performance, and 3% postural control. This review showed that aLOPD experience symmetrical weakness, concerning especially the hip and lumbar muscles. Locomotor activities are limited with a distance reduction, spatiotemporal gait parameter modification, and an increased pelvic drop and tilt. Balance disorders are also observed especially in the anteroposterior direction.

DISCUSSION

We performed the first review on motor function characteristics in aLOPD. Although a significant amount of knowledge was synthesized in this review, our study also highlighted the lack of current research on this topic. Maximal muscle strength was the only neuromuscular performance studied, and gait biomechanics and postural control were poorly explored in LOPD. Relationships between the degree of muscle weakness and motor function alterations also remain to be determined in aLOPD.

Determinants and Characterization of Locomotion in Adults with Late-Onset Pompe Disease: New Clinical Biomarkers

BACKGROUND

The late-onset form of Pompe disease (LOPD) is characterized by muscle weakness, locomotor limitations and a risk of falls. The mechanisms responsible for altered locomotion in adults with LOPD are unknown. The identification of clinical biomarkers is essential for clinical follow-up and research.

OBJECTIVES

To identify muscle determinants of impaired locomotor performance, gait stability and gait pattern, and biomechanical determinants of falls in adults with LOPD.

METHODS

In this cross-sectional, case-control study, LOPD and control participants underwent 3D gait analysis, locomotor performance tests and muscle strength measurements (isokinetic dynamometer). We explored the muscular determinants of locomotor performance (gait speed, 6-minute walk test distance and timed up and go test), gait stability (spatiotemporal gait variables) and the gait pattern. We also explored biomechanical gait determinants of falls. After intergroup comparisons, determinants were sought to use forward stepwise multiple regression.

RESULTS

Eighteen participants with LOPD and 20 control participants were included. Locomotor performance, gait stability, and the gait pattern were significantly altered in LOPD compared to control participants. Hip abductor strength was the main common determinant of locomotor performance, gait stability and pelvic instability. Hip flexor strength was the main determinant of abnormal gait kinematics at the hip and knee. Percentage duration of single support phase during the gait cycle was the main determinant of falls.

CONCLUSIONS

Hip abductor strength and percentage duration of single support during gait were the major determinants of locomotor performance, gait stability, falls and the gait pattern in LOPD. These new clinical biomarkers should therefore be systematically assessed using instrumented tools to improve the follow-up of adults with LOPD. They should also be considered in future studies to accurately assess the effects of new therapies. Hip abductor strength and single support phase should also be priority targets for rehabilitation.

Comparison of Postural Stability and Regulation among Male Athletes from Different Sports

The purpose of this study was to assess the postural control of 50 male athletes (age: 24.9 ± 4.55 years) who participate in different elite-level competitive sports. Athletes from two team sports from the third German league (ice hockey: n = 16; soccer: n = 23), and one individual sports (diving: n = 11) were included. These athletes were investigated using posturography under different conditions (e.g., stable surface, unstable surface; eyes open, eyes closed) to determine postural stability and regulation. Most of the performance maxima were found among the divers (6), followed by ice hockey (5) and soccer (4). The biggest effect of sport was found in the stability indicator, where the subject was standing on a stable surface and their eyes were closed (NC; p = 0.001, ηp2 = 0.273). This significance was observed between the soccer (17.3 ± 5.66) and diving (24.9 ± 6.98) subjects. The stability indicator had the largest significant effect (50%, 2/4). These results provide coaches and athletes insight into the postural stability and regulation of male athletes in sports with different demands on postural control. Especially for soccer players, it may be beneficial to address muscular imbalances to reduce the risk of lower extremity injuries.

Comparison of Postural Stability and Regulation among Female Athletes from Different Sports

The aim of this study was to evaluate the postural regulation of female athletes who participate in different sports under normal and high-demand conditions. Fifty-nine female athletes were classified into four specific groups based on their individual sport, which included basketball (n = 16), gymnastics (n = 10), ski jumping (n = 13), diving (n = 8), and one group of recreational athletes (n = 12). These groups were then compared using several posturographic tests under four bipedal conditions: eyes open or closed and on a stable surface or foam pad. While there were some differences between groups standing in the less demanding positions (stable surface), the higher demanding positions (unstable surface-foam pads) showed significant differences between the technical sports (ski jumping, diving, and gymnastics) and basketball and recreational athletes. Most (50%, 6/12) of significant differences were provided by sports. In contrast, the predictors age, weight, and height played only a minor role within the covariance analysis. The largest effect by sports was detected for the anterior-posterior weight distribution standing on foam pads with closed eyes (p = 0.015, ηp2 = 0.211). Ski jumping and recreational athletes showed the largest (p = 0.011) partial difference by sports for this parameter and test position. According to the parameters, the weight distribution index (WDI) was the variable with the most significant effects (50%, 6/12). These results provide coaches and athletes with a more sport specific view on postural regulation and potentially assist in identifying deficits to improve sports performance and reduce the risk of injury.