Neuroinflammation and Parkinson disease

The events that trigger the neuronal destruction and fuel the relentless progression of Parkinson disease (PD) remain unknown despite intense scrutiny and exhaustive investigation. Numerous possible mechanisms—both genetic and environmental—have been proposed, but none have been unequivocally proven, except for a relatively small number of individuals in whom genetic mutations have been identified. In this issue of Neurology®, Rugbjerg et al.¹ address one important theory of causation: that PD may be the result of an inflammatory process within the nervous system.

McGeer et al.² were the first to report evidence of inflammation within the brain in the form of microglial activation in the setting of PD. Many other investigators have subsequently confirmed and expanded on these findings.³ Although it is quite clear that neuroinflammation develops in PD, it is not at all clear why. Is the microglial activation itself the cause of cellular injury and death, in which the microglia function as neuronal assassins, or is the activation simply an appropriate and expected reaction to neuronal degeneration, …