Brainstem ventilatory dysfunction: A plausible mechanism for dyspnea in Parkinson's Disease?

Dyspnea is an under-recognized and debilitating symptom that is reported in up to 40% of patients with Parkinson's disease and may have multiple origins. Despite its frequency, it is poorly researched, and there is a general lack of understanding of the pathophysiology of dyspnea and respiratory dysfunction in PD. Consequently, a number of PD patients are labelled as having "unexplained dyspnea." Studies to date have focused mainly on evaluating ventilatory capacity and lung volumes, and little is known about the effects of the disease on the medullary and pontine ventilatory control centers within the brainstem. This is of particular relevance in view of neuropathological studies demonstrating early involvement of the dorsal medulla and other brainstem structures by the disease process. The possibility that impaired brainstem ventilatory control is a contributory mechanism for dyspnea and could be a premotor manifestation in some PD patients therefore warrants further attention. This review focuses on clinical, pathological, and experimental evidence for the involvement of brainstem respiratory centers in PD. We highlight the need for further research, particularly in PD patients with unexplained dyspnea.