An Association Between Posterior Reversible Encephalopathy Syndrome and Severe Hypercapnia in Chronic CO₂ Retention.

We discuss a 60-year-old male with a history of chronic obstructive pulmonary disease (COPD) on home oxygen and chronic carbon dioxide (CO₂) retention who initially presented with hypoxemic and hypercapnic respiratory failure and subsequent development of acute encephalopathy. Magnetic resonance imaging (MRI) of the brain showed vasogenic edema in the bilateral occipital lobes. Management with increasing supplemental oxygen and nightly bilevel positive airway pressure (BiPAP) led to rapid neurological improvement. A repeat brain MRI of the brain six days later showed improving edema in the bilateral occipital lobes. This case highlights acute and severe hypercapnia as a potentially uncommon and under-recognized trigger of PRES. It further underscores that prompt correction of hypercapnia can rapidly improve both clinical and radiographic manifestations of PRES.