Clinical and exploratory measures of multiple sclerosis

Introduction
Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. MS causes a variety of symptoms, including muscle weakness, sensory disturbances, balance disorders, and cognitive dysfunction resulting in functional impairment. Despite effective treatments, quality of life is often affected in patients diagnosed with multiple sclerosis (PwMS) due to impaired physical functions. With up to 76% requiring a walking aid or a wheel chair during the cause of the disease, walking disability is a main cause of disability in PwMS. Furthermore, approximately 75% of PwMS display bilaterally impaired manual dexterity.

Fampridine is presently the only medical drug that can improve gait performance in a subset of PwMS through, e.g., increased walking speed, higher endurance, and better self-perceived gait function.

Numerous assessment methods exists for evaluating functional performance in PwMS. However, the heterogeneous nature of MS and large day-to-day variability in general performance, challenges the clinical characterization, the monitoring of disease progression, and the evaluation of treatment responses in PwMS.

Speckle tracking ultrasonography (STU) enables non-invasive quantification of regional muscle function by evaluating the contractile properties of muscle tissue, i.e. muscle strain. STU therefore has the potential to provide a quantitative and isolated measure of muscle function in PwMS.
Three-dimensional gait analysis (3DGA) is an established method for objective quantification of kinematic, kinetic, and spatiotemporal parameters. It is the golden standard for gait analysis and can provide an evaluation of the overall quality of gait in PwMS. Biomarkers are defined as characteristics that are objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacological responses to therapeutically intervention.

These assessment methods may have the potential to provide the desired monitoring of the clinical characterization, treatment response, and disease progression.

Overall aim
To investigate the use of clinical and exploratory measures of functional and muscular performance for disease and treatment monitoring in PwMS, treated with fampridine.

Methods
For this PhD, an explorative, prospective observational cohort study (the MUST study) was conducted, from which three studies were included (study I, study II, and study III) in the current thesis. Participants were included from the outpatient MS-Clinic at Odense University Hospital from December 2018 to October 2021. Inclusion criteria were a clinically diagnosis of MS according to the McDonald criteria, age >18 years, and an Expanded Disability Status Scale (EDSS) between 4 and 7. Exclusion criteria were cancer within five years, diagnosed epilepsy, clinically significant systemic disease, MS attacks or acute decrease of functional capacity within 60 days, change in immunomodulatory treatment within 60 days, concomitant treatment with cimetidine, carvedilol, propranolol or metformin, and previous surgery in the back or lower extremities.

Participants were assessed at baseline (T0), prior to start of the medical treatment with fampridine, and at follow-up (T1) after 14 days of fampridine treatment. At both T0 and T1 participants underwent a test session including: STU, performance measures (Timed 25- Foot Walk(T25FW) , Six Spot Step Test (SSST), 2-minute Walk Test (2MWT), Nine-Hole Peg Test (9HPT), 12-Item MS Walking Scale (MSWS-12), and Oxford Shoulder Score (OSS)), neurological examination (EDSS), and blood samples. Participants in study II completed two extra test days, one day following each original visit, where 3DGA was performed. For intervention between T0 and T1 the participants received 10 mg fampridine® (Biogen, Cambridge, MA, USA) twice daily.

Findings
Study I
The objective examined, was whether muscle strain, measured by STU, can evaluate upper and lower extremity skeletal muscle function quantitatively in PwMS. Criterion validity was investigated by correlating muscle strain with the appointed gold standards for performance (T25FW and 9HPT). Furthermore, we examined the criterion validity of performance measures and compared it to criterion validity of muscle strain.

Forty-three participants were included in this cross-sectional study, conducted on baseline data. Criterion validity demonstrated no significant correlations between gold standards, and muscle strain. However, for the lower extremities, good to excellent correlations were found between gold standard (T25FW) and 2MWT and SSST, as well as a fair correlation to MSWS12. No significant correlations were detected between gold standard (9HPT) and performance measure for upper extremity.

Study II
The aims were to explore whether two weeks of treatment with fampridine would improve gait quality (using Gait Profile Score (GPS) and Gait Variable Scores (GVS)) and gait function (using performance-based tests, spatiotemporal parameters, and self-perceived gait function). Furthermore, we examined if potential changes in GPS were associated with changes in performance-based tests and self-perceived gait function.

Fourteen participants were included in this prospective observational cohort study on basis of random allocation (from the overall MUST study) to 3DGA. No fampridine-induced improvements in gait quality were demonstrated. However, for gait function, significant improvements were found in performance measures and self-perceived gait function. No changes were observed in spatiotemporal parameters. No correlations between changes in GPS and performance-based tests or self-perceived gait function were detected.

Study III
The objectives of the current study were i) to assess potential changes in relevant plasma biomarkers in PwMS after 14 days of fampridine treatment, and ii) to explore the correlations between fampridine-induced hypothesised changes in performance measures and in biomarker levels.

Twenty-seven participants were included in this prospective observational cohort study (participants who provided a blood sample at both visits). Following 14 days of fampridine treatment, significant change was only demonstrated for one plasma biomarker: Tumor Necrosis Factor-Receptor 2 (TNFR2). However, for performance measures, significant changes were found for all included measures. Correlation analysis showed i) associations between changes in SSST and changes in interleukin (IL)-2, IL-8, and IL-17 levels; ii) associations between changes in T25FW and changes in interferon (IFN)-γ, IL-2, IL-8, TNFα, and NFL levels, and iii) association between changes in MSWS-12 and changes in IL-17 levels.

Conclusion
There is an unmet need for measurements that provide more accurate disease and treatment monitoring, due to the large heterogeneity of MS. In the current PhD, we found, that with the current methodology, none of the included alternative measures display a better evaluation of muscular or functional performance, compared to several well-known and clinically used performance measures. Future studies are needed to evaluate other potential measuring tools to provide an optimal monitoring and evaluation of MS.