Refractory Nausea and Vomiting Due to Central Nervous System Injury: A Focused Review.

The area postrema (AP) is a circumventricular organ (CVO) at the base of the fourth ventricle. It has a crucial role in regulating nausea and vomiting due to its unique blood-brain barrier (BBB)-permeability and extensive neural connectivity. Here, we present two cases of area postrema syndrome (APS), a rare condition of intractable nausea and vomiting resulting from direct AP injury. Our cases each occurred in the context of infratentorial neoplasms or their treatment. Using these cases as a framework, we review the literature on central emetic pathways and propose a treatment algorithm for managing refractory nausea and vomiting of central origin. We also highlight other targets beyond conventional serotonergic, dopaminergic, or histaminergic blockade and their roles in central hyperemesis. Our literature review suggests that APS is due to the disruption of the baseline inhibitory tone of outgoing AP signals. When other options fail, our algorithm culminates in the off-label use of combined serotonergic and neurokinin-1 blockade, which is otherwise used to manage chemotherapy-induced nausea and vomiting (CINV). We believe multimodal CNS receptor blockade is efficacious in APS because it addresses the underlying central neural dysregulation, rather than solely targeting peripheral emetic triggers.