Establishing a physiological basis to multiple sclerosis-related fatigue: a case report.

Abstract

Although fatigue is a common debilitating complaint in multiple sclerosis (MS), its relationship to the cardiopulmonary exercise response has yet to be defined. A patient with MS manifested primarily by profound fatigue undergoes complete pulmonary function testing and a maximal incremental cycle ergometry study with gas exchange measurements and determination of ejection fractions. Outpatient, community hospital pulmonary function laboratory. The patient is found to have respiratory muscle weakness and a severely depressed exercise performance. The latter was associated with an early anaerobic threshold but a normal central cardiovascular response (radionuclide ventriculography), implying problems in peripheral O2 distribution/utilization. The respiratory muscle involvement, although substantial, was nonlimiting to the exercise performance. Despite its central neuropathophysiology, MS as it relates to fatigue may be associated with an abnormal peripheral exercise response, namely, problems in peripheral O2 utilization. Such a concept could prove invaluable as it would provide a physiological basis for defining the severity and therapy of "MS fatigue."