Therefore, it is important to quantify the value of extended outpatient EEG studies with respect to diagnostic yield. Additionally, the Centers for Medicare and Medicaid Services (CMS) continue to evaluate the value of neurologic procedures in an effort to control costs. This is an important consideration as repeated, prolonged, and take-home ambulatory recordings may be intrusive for the patient, and may impact laboratory efficiency. While longer EEGs likely render a higher yield of IEDs, this has not been extensively studied in a comparative manner. 7 Based on these recommendations, many routine outpatient EEGs last 20–30 minutes. 6 The International League Against Epilepsy recommends recording for at least 30 minutes. The American Clinical Neurophysiology Society recommends a minimum of 20 minutes of artifact-free recording to evaluate baseline wakefulness, but concedes that longer studies may be needed for activation procedures and sleep. The duration of standard outpatient EEG varies across practices. 1, – 4 Prolonged ambulatory EEGs are also sometimes used to identify interictal epileptiform discharges (IEDs) in patients with normal or nonepileptiform routine EEGs. This yield may be increased by performing serial recordings. Only 29%–55% of epilepsy patients have epileptiform abnormalities on a single routine outpatient EEG. Routine outpatient EEGs in epilepsy are frequently nondiagnostic. EEG is a cornerstone in diagnosing epilepsy and other paroxysmal events.

Epilepsy eeg vs normal eeg