Toxic and Metabolic Encephalopathies

Toxic and metabolic encephalopathies are the main causes for alterations of consciousness in patients admitted to the emergency department. The clinical presentations are diverse, including alterations of cognition and consciousness as well as various motor signs, and even focal neurological deficits such as hemiparesis or dysphasia. Therefore, making a diagnosis of a toxic or metabolic encephalopathy requires a thorough differential diagnostic work-up, including especially the exclusion of structural alterations of the brain. Neurologists in the emergency department face encephalopathies most frequently caused by hypo- or hyperglycemia or alterations of water and electrolyte metabolism. Hepatic encephalopathy in patients with acute or chronic liver failure and uremic encephalopathy need neurological expertise as well. This chapter addresses the clinical characteristics of these disorders, basic pathophysiology, differential diagnosis, and treatment.