Primary fatigue (unique to multiple sclerosis) involves no precipitating activity, is worsened by heat or humidity, and is worse in the early afternoon. 40 % of MS patients report it as their most disabling symptom. This fatigue may be constant in 30 % of affected individuals.
The cause of primary fatigue is unknown.
Treatment options include : cooling, aerobic and strength training, energy conservation, mindfulness, relaxation therapy, magnetic therapy, transcranial stimulation, and drugs.
Drug therapy to treat fatigue include : amantadine, modafinil, armodafinil, gingko biloba, methylphenidate and amphetamines.
Comorbid conditions must be addressed : depression, anemia, thyroid disease, disrupted sleep, medication side effects, motor disability with increased energy use. (Continuum 2016;22(3):815-836)