The utility of prolonged outpatient ambulatory EEG

Abstract

PurposeILAE guidelines recommend the use of prolonged EEG where the diagnosis of epilepsy or the classification of the seizure syndrome is proving difficult. Due to its limited provision, video EEG monitoring is unavailable to many patients under investigation1. The aim of this study was to examine the utility of the alternate investigation of outpatient ambulatory EEG. MethodsIn this retrospective study we analysed 324 consecutive prolonged outpatient ambulatory EEGs lasting 72–96h (4–5 days), without medication withdrawal. EEG data and the clinical record were reviewed to investigate the utility of the investigation. ResultsOf 324 studies: 219 (68%) studies gave positive data, 116 (36%) showed interictal epileptiform discharges (IEDs), 167 (52%) had events. 105 (32%) studies were normal. Overall 51% of studies changed management of which 22% of studies changed the diagnosis and 29% of studies refined the diagnosis by classifying the epilepsy into focal or generalised. ConclusionThe present study confirms the diagnostic utility of outpatient ambulatory EEG in the diagnosis of paroxysmal events.