Stephanie Crenshaw Marchesi
PhD Dissertation Defense
Advisor: Todd Royer
Friday, December 1, 2006
3:00pm, 003 CSB
(Refreshments prior)
The Effects of Fatigue and Disease Severity on Gait Mechanics in Subjects with Multiple Sclerosis
ABSTRACT
Multiple sclerosis (MS), an autoimmune disease of the central nervous system, affects approximately 400,000 Americans. The disease is characterized by breakdown of myelin, the protective sheath surrounding nerves. Symptoms of MS can be sensory and/or motor and depend on the location of the broken down myelin patches (called lesions). Symptoms vary both within and between patients with MS, making the disease progress highly variable. The most common symptom complaints are fatigue and difficulty walking. Fatigue often increases throughout the day, making walking even more difficult. The high degree of variability due to both symptoms and fatigue may make it difficult to track changes over time.
The presented research aimed to determine the effects of fatigue and disease severity on gait in subjects with Multiple Sclerosis. We wanted to know if the variable nature of the disease affected gait mechanics and whether the changes were related to fatigue and disease severity.
Prior work suggested that discrete parameters and variability measures might not be sufficient to distinguish among the different levels of fatigue and disease severity. Therefore, a new analysis method was developed in order to assess joint symmetry and normalcy values. The analysis method utilizes the entire waveform to compare two limbs to determine symmetry (the two limbs are intra-subject) and normalcy (the two limbs inter-subject).
The aims of the study were:
1. To determine the differences in gait between subjects with Multiple Sclerosis and healthy
controls
2. To determine the effects of fatigue on gait parameters in subjects with MS
3. To determine the relationship between disease severity and gait patterns in subjects with MS
4. To determine the relationship between disease severity and change from fresh to fatigue
Twenty-eight subjects with MS and twenty-eight healthy control subjects participated in this study. Three dimensional gait analyses were conducted for each subject during walking on a ground reaction force measuring treadmill. MS subjects were given a choice of five different speeds, and walked at the one that felt most comfortable to them. The subjects with MS were tested under both fresh and fatigued conditions, while the healthy control subjects were tested at each of the speeds at which the MS subjects walked.
We hypothesized that select sagittal plane ankle, knee and hip angle, moment and power variables of MS subjects would be more variable, less symmetric, and less “normal” than that of healthy control subjects. Results from the gait study supported this hypothesis. Subjects with MS were approximately 20% more variable for joint angles and moments compared to healthy control subjects. Joint asymmetry was between 140% and 260% greater for the MS subject compared to controls and all normalcy measures were greater (worse) for MS subjects compared to controls.
Percent differences between MS and control groups ranged from 35% for hip joint power normalcy to 866% for knee joint angle normalcy.
The hypothesis that the gait patterns of subjects with MS would be different, more variable, less symmetric, and less “normal” in a fatigued state than in a fresh state was not supported.
There were small statistically significant increases of approximately 15% in variability from fresh to

fatigued conditions, but the discrete parameters, symmetry and normalcy parameters were not significantly changed from a fresh to a fatigued condition.
Though walking speed decreased with increases in disease severity and the change in self reported fatigue increased with increases in disease severity, few of the gait variables were themselves related to disease severity. This may be due to the variable nature of the disease itself, making relationships between gait parameters and disease severity difficult to determine.
With this work, we hoped to develop a greater understanding of the relationships between fatigue and disease severity and functional mobility measures in order to define meaningful changes due to treatment within the MS population. We confirmed previous research that the gait of subjects with MS is different from that of healthy controls, and that self reported increases in fatigue are not necessarily associated with changes in physical performance measures. Disease severity as measured by the EDSS and the MSFC does not correlate well with the gait parameters measured in this study. Different measures of disease classification should be investigated to further examine gait changes over time. Subjects could perhaps be grouped by which functional system is affected or lesion location in the CNS in order to determine the relationship between MS and gait patterns.