Muscle And Nerve Excitability In Myotonic Dystrophy.
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Type
ThesisThesis type
Doctor of PhilosophyAuthor/s
Boland-Freitas, RobertAbstract
Abstract: Myotonic dystrophy is the most common form of muscular dystrophy in adults. Both subtypes, Type 1 (DM1) and Type 2 (DM2), affect multiple body systems. Myotonia and muscle atrophy are common to DM1 and DM2 and contribute to morbidity. The main purpose of this thesis was ...
See moreAbstract: Myotonic dystrophy is the most common form of muscular dystrophy in adults. Both subtypes, Type 1 (DM1) and Type 2 (DM2), affect multiple body systems. Myotonia and muscle atrophy are common to DM1 and DM2 and contribute to morbidity. The main purpose of this thesis was to elucidate aspects of muscle and nerve function in these conditions. To do this, the neurophysiological techniques of skeletal muscle and axonal excitability assessment, in addition to quantitative sensory thermal thresholds testing were used. Given that relationships between serum electrolyte levels and muscle excitability measures have been found in disease states, in this thesis their assessment was undertaken in healthy individuals. The inter-rater reliability of thermal threshold assessment was also examined, as this method was used to assess small nerve fibre function in DM1 and DM2. Significant muscle excitability differences were found between persons with advanced DM1 and healthy individuals, consistent with sodium-potassium pump dysfunction. Additionally, chloride channel dysfunction was demonstrated in both advanced DM1 and in DM2. It is concluded the technique may merit use as a disease biomarker and aid in diagnosis. Serum electrolyte concentration variation between disease groups and healthy individuals is concluded to be unlikely to account for differences observed between muscle disease and normal groups, despite significant correlations being demonstrated between some measures and ions. Increases in inward rectification, possibly reflecting neural adaptation to muscle weakness, and nodal sodium currents we found on advanced DM1 motor axon excitability. Sensory nerve excitability was not altered, though larger studies of lower limb nerves could increase sensitivity. Perception of thermal change was found to be abnormal in the upper and lower extremities in DM1, consistent with small fibre sensory neuropathy that precedes or occurs in isolation from large fibre nerve dysfunction.
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See moreAbstract: Myotonic dystrophy is the most common form of muscular dystrophy in adults. Both subtypes, Type 1 (DM1) and Type 2 (DM2), affect multiple body systems. Myotonia and muscle atrophy are common to DM1 and DM2 and contribute to morbidity. The main purpose of this thesis was to elucidate aspects of muscle and nerve function in these conditions. To do this, the neurophysiological techniques of skeletal muscle and axonal excitability assessment, in addition to quantitative sensory thermal thresholds testing were used. Given that relationships between serum electrolyte levels and muscle excitability measures have been found in disease states, in this thesis their assessment was undertaken in healthy individuals. The inter-rater reliability of thermal threshold assessment was also examined, as this method was used to assess small nerve fibre function in DM1 and DM2. Significant muscle excitability differences were found between persons with advanced DM1 and healthy individuals, consistent with sodium-potassium pump dysfunction. Additionally, chloride channel dysfunction was demonstrated in both advanced DM1 and in DM2. It is concluded the technique may merit use as a disease biomarker and aid in diagnosis. Serum electrolyte concentration variation between disease groups and healthy individuals is concluded to be unlikely to account for differences observed between muscle disease and normal groups, despite significant correlations being demonstrated between some measures and ions. Increases in inward rectification, possibly reflecting neural adaptation to muscle weakness, and nodal sodium currents we found on advanced DM1 motor axon excitability. Sensory nerve excitability was not altered, though larger studies of lower limb nerves could increase sensitivity. Perception of thermal change was found to be abnormal in the upper and lower extremities in DM1, consistent with small fibre sensory neuropathy that precedes or occurs in isolation from large fibre nerve dysfunction.
See less
Date
2019-06-25Licence
The author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission.Faculty/School
Faculty of Medicine and HealthAwarding institution
The University of SydneyShare