Chapter 1 - Overview and Definitions

Abstract

Acute encephalopathy in infancy and childhood is defined as a rapidly progressive dysfunction of the brain with noninflammatory edematous changes in infants and children. This neurologic syndrome causes rapid, accelerating, and protracted deterioration of consciousness, frequently following convulsive seizures with febrile illness. Differential diagnosis includes epileptic conditions such as febrile/nonfebrile convulsive status epilepticus, acute hypoxia and/or ischemia, traumatic brain injury, cerebrovascular disorders, central nervous system (CNS) infections, immunologic CNS disorders, and brain tumors. Four types of categories have been proposed based on the plausible pathomechanism, including metabolic errors, cytokine storm, neuronal excitotoxic crisis, and other obscure pathogeneses. The subtype related with inherited metabolic disorders is suggested by the abnormalities in the initial routine laboratory tests such as blood level of glucose, ammonia, lactate, and ketone body as well as plasma acid-base status. Marked elevation of the serum and cerebrospinal fluid concentrations of inflammatory cytokines such as tumor necrosis factor alpha and interleukin-6 suggest the subtype related with cytokine storm. Acute infantile encephalopathy predominantly affecting the frontal lobes or acute encephalopathy with biphasic seizures and late reduced diffusion as well as hemiconvulsion-hemiplegia-epilepsy syndrome fall into the category of neuronal excitotoxic crisis, which exhibit characteristic patterns of magnetic resonance images and the distribution of cerebral flow using single photon emission computed tomography. Prompt diagnosis and management are necessary to minimize the neurologic sequelae caused by this catastrophic neurologic syndrome with rapidly progressive manner.