Exploring Muscle Structure, Function, and Gait Patterns in People with Distal Hereditary Motor Neuropathy: Natural History and the Effect of Rehabilitation Interventions

Abstract

Background: Distal Hereditary Motor Neuropathy (DHMN) is a rare heterogenous inherited neuromuscular disorder. It is characterised by distal progressive weakness. Objectives: This thesis provides preliminary longitudinal data to describe the natural history of DHMN in terms of muscle structure, muscle strength, and gait parameters, also to investigate the effect of commonly used rehabilitation interventions. Methods: DHMN adult participants underwent the following measures: MRI scans of the foot, calf, and thigh muscles, isokinetic and isometric strength measures of the lower limb using dynamometer, 3D motion analysis to capture kinetic and kinematic data of walking gait. For direct comparison, matched health controls underwent the same measures. Measures were repeated after 6 and 12 months to explore the natural history of the disease. DHMN participants underwent additional gait analysis wearing bilateral carbon fibre ankle foot orthoses to explore the effect on gait. Eligible DHMN participants were prescribed a home based resistance training program, and the response to training was analysed by the same measures after 6 months of training. Results: The study identified significant progressive muscle atrophy and increased intramuscular fat accumulation at the calf in DHMN participants, with a notable decline in muscle strength over time and altered gait mechanics. The use of ankle-foot orthoses showed improvements in gait stability, while the resistance training program indicated potential benefits in maintaining muscle function, but adherence was a key challenge. Conclusion: The preliminary data from this study provide valuable insights into the natural history of DHMN, highlighting the progressive nature of muscle degeneration and functional decline. These findings offer useful guidance for health practitioners in managing DHMN and emphasize the need for targeted rehabilitation interventions to improve patient outcomes. Future research should focus on longer-term studies with larger cohorts to validate these findings and further explore effective management strategies.