The Biological Underpinnings of Fatigue in People with MS

For many patients with multiple sclerosis (MS), severe fatigue is the most disabling symptom of the illness and a common cause of absence from work. Boston investigators speculated that activation of the brain's innate immune system — particularly microglial cells and astrocytes — might be a cause of fatigue. They studied 12 patients with either relapsing–remitting or secondary progressive MS; for each patient, degree of fatigue was measured using a validated scale, and positron-emission tomography was used to measure the level of microglial/astrocyte activation. The researchers also evaluated 10 healthy controls.

The degree of immune activation in several brain areas — particularly the substantia nigra — was significantly higher in MS patie…