Fatigue is just one on the list of crappy things patients deal with—it’s a feeling of exhaustion or being worn down. It can be caused by explainable things like side effects from medication or the extra effort put into daily tasks that were once easy. Or, it can be caused by seemingly nothing, coming on after a good night’s sleep.
Despite having a catch-all name, there are two types of MS fatigue: primary fatigue, and secondary fatigue. Primary fatigue is caused by damage to the central nervous system, e.g. demyelination. Secondary fatigue could be caused by other symptoms of MS or be a side effect of MS treatments.