Dissertation
The effects of gait training combined with 4 mA cerebellar transcranial direct current stimulation in people with multiple sclerosis
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2023
DOI: 10.25820/etd.007048
Abstract
People with MS (PwMS) experience various motor and/or sensory symptoms as areas of demyelination and lesions may present throughout the central nervous system. However, mobility impairments, particularly walking dysfunction are continually reported to be the most life-altering consequences of the disease. Unfortunately, most pharmacological interventions for PwMS aim to decrease demyelination and lesion progression and fail to effectively improve symptoms, such as gait impairments, and/or have significant side effects. Therefore, many PwMS choose to not take medications and instead rely on lifestyle interventions. However, recommendations for this approach have not been established.
Transcranial direct current stimulation (tDCS) is thought to alter cortical excitability and has been used previously to improve MS-related symptoms, with variable results. However, no studies have assessed whether tDCS can effectively alter leg muscle activation. Moreover, most previous studies have used tDCS intensities ≤ 2 mA, despite evidence that higher intensities may be warranted in PwMS. Therefore, in Chapter 2, a case series was performed to evaluate the effects of a single sessions of 3 mA and Sham tDCS over the motor cortex (M1) on leg muscle glucose uptake during walking in PwMS using positron emission tomography (PET) with the glucose analog [18F] fluorodeoxyglucose (FDG). The results demonstrated various alterations in glucose uptake and glucose uptake asymmetries in individual muscles and muscle groups, with the greatest changes in subjects who were not physically active. These results suggest that physical activity levels may be important to consider in tDCS studies in PwMS as regularly exercising may be sufficient to improve or maintain motor performance.
The results of Chapter 2 were in line with the tDCS literature, showing variable results between subjects. It is still unclear which tDCS parameters are most effective to increase motor performance in PwMS, particularly stimulation intensity and target brain region. Specifically, the use of higher intensities (≥ 2 mA) may be warranted to in PwMS due to demonstrated cerebral hypometabolism and decreased neuronal conduction velocity. Moreover, the cerebellum may be an important brain region to target due to its vital role in gait and balance, but only a few studies have explored this possibility. Additionally, while the pilot studies in Chapter 2 evaluated the effects of a single session of tDCS, multiple sessions may be necessary to induce lasting improvements in MS-related symptoms. Lastly, pairing tDCS with task-specific exercise (e.g., gait training) interventions may be important to improve mobility in PwMS.
Therefore, in Chapter 3, the effects of 9 sessions of either 4 mA or Sham tDCS over the cerebellum combined with treadmill-based gait training on walking and balance performance as well as fatigue and quality of life were assessed. In addition, alterations in brain and leg muscle glucose uptake were evaluated via PET/FDG as a potential underlying mechanism of improvements. The results demonstrated improvements in walking performance, minimal alterations in balance performance, and no change in quality of life. Importantly, the effects of the gait training on functional outcomes were not amplified by tDCS. However, although there were no differences at post-testing, the 4 mA tDCS group did report an increase in perceived fatigability at the 2-week follow-up, while the Sham group showed a decrease in perceived fatigability at the 4-week follow-up. Lastly, there were few alterations in brain and leg glucose uptake, with no differences demonstrated between the groups.
The contrasting results of Chapters 2 and 3 may be due to the different tDCS parameters used, particularly the stimulation site (i.e., motor cortex vs. cerebellum) or because Chapter 2 assessed individual differences after active and Sham stimulation while Chapter 3 evaluated group differences (i.e., active vs. Sham groups). Overall, these data suggest that gait-specific exercise interventions may improve walking performance in PwMS. However, these improvements may not result in alterations in other MS-related symptoms, including balance deficits, fatigue, and quality of life. Moreover, tDCS may improve brain and leg glucose metabolism in individual PwMS, particularly those with higher levels of disability and low levels of physical activity, but this technique may not be effective at the group level for PwMS due to high levels of variability in disability status.
In conclusion, these data demonstrate the variability of tDCS interventions on functional outcomes and, therefore, provides insight to why various interventions may be necessary to improve MS symptoms, particularly across the disability spectrum. However, the results of these studies demonstrate that engaging in physical activity may effectively improve or maintain motor performance in PwMS. Specifically, gait training may be an important intervention to improve mobility in PwMS. However, it is unclear if tDCS, particularly placed over the cerebellum, can significantly amplify the effects of exercise interventions, potentially due to the variability in both MS-related disability and tDCS outcomes.
Details
- Title: Subtitle
- The effects of gait training combined with 4 mA cerebellar transcranial direct current stimulation in people with multiple sclerosis
- Creators
- Alexandra Courtney Fietsam
- Contributors
- Warren Darling (Advisor)John Kamholz (Committee Member)Jacob Sosnoff (Committee Member)Nathaniel Jenkins (Committee Member)Gary Pierce (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Health and Human Physiology
- Date degree season
- Summer 2023
- DOI
- 10.25820/etd.007048
- Publisher
- University of Iowa
- Number of pages
- xi, 172 pages
- Copyright
- Copyright 2023 Alexandra Courtney Fietsam
- Language
- English
- Date submitted
- 07/24/2023
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 128-158).
- Public Abstract (ETD)
Walking dysfunction is a common impairment in people with multiple sclerosis (PwMS). However, current treatments fail to effectively improve physical symptoms. Therefore, many PwMS use alternative therapies. Transcranial direct current stimulation (tDCS) may improve walking performance by increasing the ability of neurons to send signals to exercising muscles. Moreover, combining multiple sessions of tDCS with physical activity may be important to improve walking performance. This dissertation investigates the effects tDCS alone as well as in combination with exercise training on mobility and glucose uptake (i.e., energy use) in exercising leg muscles. In this regard, Chapter 2 reports the effects of a single session of 3 mA and Sham (i.e., placebo) tDCS over the motor cortex, an area of the brain that directs body movement, on leg muscle glucose uptake. The results suggested tDCS might alter glucose uptake in individual subjects, particularly in PwMS who are not physically active. Moreover, it may be important to use multiple sessions of tDCS, especially in combination with exercise training, as well as to explore the effects of different tDCS intensities and stimulation locations. Therefore, Chapter 3 reports the effects of 9 sessions of either 4 mA or Sham tDCS over the cerebellum on walking and balance performance, in addition to fatigue and quality of life. Additionally, alterations in glucose metabolism in the brain and leg muscles were evaluated. The results revealed that gait training improved walking performance, but not other functional outcomes or glucose uptake, and that these effects were not amplified by tDCS.
- Academic Unit
- Center for Social Science Innovation; Health, Sport, and Human Physiology
- Record Identifier
- 9984454540402771
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