Metabolic Derangement and Vitamin Deficiencies.

Metabolic derangements and vitamin deficiencies represent one category of important, potentially reversible causes of acute encephalopathy, also termed "potentially reversible acute encephalopathic syndromes." This article summarizes their underlying pathophysiology and distinctive neuroimaging features, emphasizing disorders of glucose, ammonia, bilirubin, calcium-phosphorus metabolism, complex B-vitamin deficiencies, uremia, and osmotic stress. Magnetic resonance-particularly diffusion-weighted imaging-plays a pivotal role in diagnosis, prognostication, and therapeutic monitoring. Recognition of characteristic imaging patterns, such as "dark white matter" in hyperglycemia, the "lentiform fork sign" in uremia, and T1 pallidal hyperintensity in bilirubin toxicity, enables timely management and improved outcomes through an integrated clinicoradiologic approach.