Special Electroencephalography

Ambulatory EEG (24–48 hour outpatient recording) is covered when routine EEG and clinical evaluation are insufficient to diagnose or classify suspected seizures, to differentiate seizures from cardiac or psychiatric events, to identify absence seizures, or to localize seizure onset when clinically useful. Outpatient monitoring is generally expected to be diagnostic within 48 hours; monitoring beyond 48 hours requires documented medical necessity and the 48-hour outpatient limit does not apply to inpatient presurgical or medication-withdrawal evaluations. Studies are not covered for neonates or unattended/non-cooperative patients, for localization when bilateral foci or rapid generalization are present, nor for routine repetition after the diagnosis is established or routine therapeutic monitoring.

"Ambulatory EEG is indicated when a seizure diathesis is suspected but not defined by history, physical exam, or routine resting EEG."