Acute and Subacute Encephalopathies

One of the most vexing and serious problems faced by the neurologist is the diagnosis and management of patients with rapidly worsening brain failure. By definition, such disorders worsen day by day, often rendering patients helpless within a few weeks or even less. These disorders span the spectrum of neurologic and medical illnesses making it a special challenge for the clinician. Because many may respond to specific therapies, it is critically important to make the correct diagnosis and to initiate therapy rapidly. Other forms of subacute encephalopathy are currently untreatable, but even then, it is important to patients and their families to understand the nature of the decline, its probable cause, and whether any effective treatment exists.

The major categories of rapidly progressive encephalopathies include immune-mediated disorders (including paraneoplastic diseases), endocrinopathies, tumors, vitamin and mineral deficiencies, intoxications, failure of other organs (including the liver, kidneys, heart, and lungs), hematologic disorders, infectious diseases, cardiovascular diseases, (including ischemic hypoxia and toxemia of pregnancy), hydrocephalus, thermal control disorders, and psychiatric illnesses. When faced with this dizzying array of possibilities, it is important for the neurologist to have an organized approach and to understand the most likely and important causes of the patient's worsening mental state.

In this issue of Seminars in Neurology, esteemed experts present their perspectives on the most common causes of the syndrome of rapidly progressive encephalopathy. Uremic encephalopathy and electrolyte disorders are covered by the team of Julian Seifter, a distinguished nephrologist, and myself, a neurologist. Benign immune-mediated encephalopathies are covered by Eoin Flanagan and Richard Caselli; those associated with cancer (paraneoplastic diseases) are handled with her usual aplomb by Amy Pruitt. Neeraj Kumar details the important deficiency states, and toxic encephalopathies are covered by Michael Dobbs. Suzette LaRoche gives a beautiful exposition of how and when seizures can produce an acute or subacute encephalopathy. Steve Feske reveals his wisdom and long experiences with the toxemia of pregnancy by demystifying the endothelial diseases, which produce the familiar neuroimaging picture of reversible posterior leukoencephalopathy; and finally, Wei Xiong, Robert Hoersh, and Romergryko Deocadin provide important guidelines for the clinician in assessing and treating the postcardiac arrest patient.

All in all, by reading this volume the experienced neurologist can hope to become more facile at recognizing, correctly diagnosing, prognosticating, and treating the most important and common acute and subacute encephalopathies.