Encephalopathy

Abstract

The term encephalopathy describes a general alteration in brain function manifesting as an attentional disorder anywhere within the continuum between a hyperalert agitated state and coma, and typically refers to the commonly encountered clinical scenario of diffuse brain dysfunction felt to be due to a systemic, metabolic, or toxic derangement. This chapter discusses an approach to the emergency evaluation and management of patients with encephalopathy, with an emphasis on those causes of toxicmetabolic encephalopathy that will lead to irreversible neurological dysfunction if not recognized and treated urgently, as well as those encephalopathies whose recognition might lead to more prompt diagnosis and treatment of the causative medical illness. The encephalopathies discussed in this chapter are divided into four common, though overlapping, scenarios the neurologist is likely to encounter in clinical practice: Encephalopathy from metabolic disorder or deficiency, encephalopathy due to a severe systemic illness or organ failure, encephalopathy due to medication-related toxicity, and encephalopathies diagnosable primarily by findings on brain imaging. In many cases a specific etiological diagnosis can be made—via history, examination, laboratory studies, and in some cases, imaging—which may lead to specific medical intervention and more rapid clinical resolution, and may help prevent irreversible neurologic dysfunction. Since patients with diffuse, toxic-metabolic encephalopathies are medically—and secondarily neurologically—ill, the evaluation and management of patients with diffuse encephalopathies represents a unique and important opportunity for the neurologist to positively impact the medical management, and both the neurological and medical recovery, of these systemically ill patients.