EEG in neurological conditions other than epilepsy: when does it help, what does it add?

A lthough the electroencephalogram (EEG) is a reliable test to assess cerebral function, its value in diagnosis and evaluation of neurological conditions apart from epilepsy has been largely superceded in recent years by other investigations with greater specificity and sensitivity. Is EEG still worthwhile, and in which cases can it provide information that affects management? Broadly speaking, EEG is most important in patients with impaired consciousness or altered mental state (table 1): c Where seizures or non-convulsive status epilepticus (NCSE) may be a contributing factor c To demonstrate functional disturbance when cerebral dysfunction is evident and structural imaging is normal c To detect focal or lateralised abnormalities which could suggest a structural basis for an encephalopathy c To identify diagnostic EEG patterns in appropriate clinical settings, such as sporadic Creutzfeldt-Jakob disease (CJD).