Fatigue is one of the most common and disabling symptoms of multiple sclerosis (MS).1 Not only does fatigue affect up to 87% of patients with MS but as many as 40% of patients with MS regard fatigue to be their most disabling symptom.2 Although several therapies have shown some promise in the treatment of fatigue in patients with MS, the lack of a truly effective treatment for this symptom may be due to the underlying pathophysiology for MS fatigue still being debated.