Clinical utility of electroencephalography in encephalopathy

Abstract

Encephalopathy is an entity characterized by temporary or permanent disorder of brain functions: memory, memorising, perception, personality disorders, psychomotoral hyperactivity, agitation, hallucination, illusion, delirium, disorientation, seizures, asterixis, myoclonismus, coma and death. Encephalopathy causes are various and electroencephalography (EEG) represents an important encephalopathy diagnostic procedures, despite low specificity. Typically, EEG manifestations of encephalopathy are loss of normal rhythms and slow diffuse brain activity. More specific patterns are: triphasic waves in hepatic or uremic encephalopathy and in Jakob–Creutzfeldt disease or tricyclic waves discharge with frontal or fronto-occipital gradient after aggressive hemodialysis. Spikes, triphasic waves, intermittent rhythmic delta activity (IRDA), localized frontally (FIRDA) may be observed in Hashimoto encephalopathy. FIRDA may be observed during episodes of hypoglucemia, hypernatremia, hepatic encephalopathy. Hyperglycemia may provoke periodic lateralized epyleptic discharges (PLEDs). PLEDs and generalized periodic epileptic discharges (GPEDs) may be observed in patients with viral encephalitis and hypoxic encephalopathy. Burst suppression pattern (BSP) in anoxic patients and electro-cortical inactivity in hypothermia are the usual signs of fatal prognosis. Specificity of EEG in encephalopathy, despite limitations, may offer clinical utility in estimation of diseases’ severity and prognosis.