An evidence-based approach to proper diagnostic use of the electroencephalogram for suspected seizures.

The EEG has strengths and limitations, which must be known to use it properly. An important reason to order an EEG is to help differentiate seizures from other etiologies of paroxysmal events that may or may not be associated with loss of consciousness. Like any other diagnostic test, the EEG refines the probability of a condition, and is normally used to support the clinical diagnosis of seizures, which relies mainly on a patient's history. The EEG itself neither proves nor excludes a diagnosis of seizures, but is nevertheless essential in the diagnostic workup and proper classification of epileptic seizures and syndromes. On the basis of the most relevant articles available in the literature, this article describes an evidence-based approach to proper use of the EEG in the diagnosis of seizures in an ambulatory care setting and presents concepts such as pretest and posttest probability and sensitivity and specificity with respect to EEG as a diagnostic test.