2012
American Epilepsy Society (Abst. 1.060)
Ambulatory EEG monitoring with video in adults; yield and clinical utility
Authors: E. Fertig, E. Feoli, M. Fleming, C. Lambrakis, O. Laban-Grant, S. Mesad, J. Politsky, M. Lancman
Rationale:
Inpatient video-EEG monitoring is the gold standard for differentiation of epileptic events from other phenomenon, and longer recording allows for detection of rare interictal epileptiform discharges (IEDs) and subclinical seizures. Inpatient admission has advantages, including observed AED taper, but disadvantages, such as the risk of hospital-associated infection, patient discomfort and cost. Ambulatory EEG (without video) cannot distinguish electroclinical from subclinical seizures, nor non-epileptic seizures from seizures without an ictal correlate (e.g., frontal lobe seizures). Ambulatory video-EEG (AVEEG) is now possible, but its yield and impact on management has not been examined.
Methods:
A retrospective review of 307 consecutive studies in adults 18 yrs or older was performed. A 72 hour AVEEG was acquired with synchronized digital video and EEG (non-invasive, scalp, 10/20 system) with a button for subjective events. Relevant clinical data was abstracted from the chart, including the indication, and if results lead to change in AEDs or management overall (e.g., driving recommendations).
Results:
Indications were 145 to assess response to treatment for epilepsy (A), 106 to assess spells without a previous epilepsy diagnosis (B), 11 to assess new spells with a previous epilepsy diagnosis (C), 39 studies to guide the decision to reduce or withdraw AEDs after prolonged seizure freedom (D), and 6 unclassified (E). Studies revealed interictal epileptiform abnormalities (IEDs) in 101 (33%); focal slowing in 80 (26%), events of any type in 56 (18%). Of studies with events (some had more than one type), 12 (21%) had electroclinical seizures, 14 (25%) had subclinical seizures, 2 (4%) had seizures with only clinical manifestations, 20 (36%) had psychogenic non-epileptic seizures (PNES), 6 (11%) had other types of non-epileptic events (e.g., syncope). Six had events solely off video (3 with ictal correlate) which could not be fully classified. Diagnostic studies (B+C) yielded a new diagnosis in 28%. Study type D revealed IEDs in 28% and seizures in 10% (50% subclinical). For all studies, AEDs changed in 21% and management in 30%. AED change was significantly associated with event of any type (p < 0.001) and any epileptic seizure (p<0.001), but not IEDs (p=0.0344), focal slowing (p=0.7980) or PNES (0.77); and change in overall management was significantly associated with event of any type (p<0.001), any epileptic seizure (p<0.001), PNES (p<0.001) but not focal slowing (p<0.5935) or IED (p=0.9361).
Conclusions:
Nearly one-third of AVEEG studies lead to a new diagnosis, a third of the time for PNES, which highlights the need for video. Events, both epileptic and non-epileptic, had a more robust effect on clinical decision-making than interictal findings, leading to management changes in one-third. Notably, 10% of reportedly seizure free candidates for AED withdrawal were in fact having seizures. In summary, for studies in adults without need for observed AED taper, AVEEG is useful, but further study is needed on patient selection and timing, and impact on clinical outcomes.