Electroencephalography in metabolic disorders, intoxications, and epileptic encephalopathies

This chapter provides a systematic overview of the diagnostic and prognostic value of electroencephalography (EEG) in adult patients with different types of encephalopathies in association with metabolic, toxic, and epileptic disorders. Most encephalopathies present with a fluctuating course characterized by typical but not pathognomonic symptoms such as cognitive impairment, altered mental status or confusion, lethargy, decreased or rarely increased motor activity, and disturbed sleep/wake cycles. EEG enables rapid, bedside electrophysiological monitoring, providing dynamic real-time information on the integrity of neocortical brain activity. Hence, EEG complements clinical and neuroimaging assessments of encephalopathic patients. Progressive slowing of EEG background activity with increasing cerebral dysfunction, emergence of intermittent transients, electrographic seizures, and impaired background reactivity to external stimuli all provide important diagnostic and prognostic information to guide medical management.