The reliability of objective fatigue measures in Multiple Sclerosis Patients

Fatigue is one of the most distressing symptoms of Multiple Sclerosis, impairing quality of life, work performance and social interactions. Moreover, it is difficult to objectively assess, and is often evaluated via subjective questionnaire; however, objective metrics are highly desirable. Objective of this paper is to implement a differential fatigue measure based on evoked potentials, and assess its reliability and coherence with walking tests and subjective questionnaires. Method: the Regional Multiple Sclerosis Reference Centre, San Luigi Gonzaga Hospital, Italy, is carrying out tests in order to assess the effectiveness of 4- amino-pyridine for fatigue relief. This work takes as input evoked potential waveforms and implements an algorithm to perform suitable signal processing and provide a fatigue index and a related reliability metric. This information is put in relationship with the walking test results and the subjective fatigue scores. Preliminary results reveal that fatigue measures based on evoked potentials, subject to proper data processing, are not always coherent with subjective ques- tionnaires and walking tests. This may be due to the fact that fatigue cannot be reduced to a mere muscular/conduction problem, and the walking tests are heavily conditioned by the disability degree. Moreover, the reliability of such measures carries not trivial information that should be carefully considered. As a conclusion, evoked potentials and gait analysis represent a good comple- ment of subjective questionnaires as for fatigue assessment. The significance of our work lies in the fact that reliable fatigue measures can help improving the patients' quality of life, allowing assessment of the therapy effectiveness and posology.