Abstracts

Rationale: Background: The University of New Mexico Hospital (UNMH) inpatient epilepsy monitoring unit (EMU) covers a wide under-served area. Prolonged EEG monitoring is required to accurately diagnose, localize and classify epilepsy for treatment and prognostic purposes. Current waiting time at UNMH EMU is approximately 6 months. Outpatient ambulatory EEG may serve as a cost-effective and convenient alternative to inpatient epilepsy-EEG monitoring. Objective: To investigate our institution's experience, utilization, and indications for outpatient aEEG in the diagnosis and management of epilepsy and to assess the diagnostic yield and limitations of aEEG. Methods: Retrospective electronic medical record and EEG database review of all consecutive pediatric and adult patients undergoing aEEG at UNMH from January 2008 to April 2014. Variables analyzed included age, gender, presence of interictal epileptiform discharges (IEDs), EEG background abnormalities, habitual and/or non-habitual events, diagnostic yield and limitations. Studies with insufficient information or technical failures were excluded. Results: A total of 63 aEEGs without video were performed at our institution, 46 met inclusion criteria: 61 % pediatric (mean age 10.4 years + 4.9 SD) and 39% adults (mean age 47.8 years + 11.9 SD), 52% were female and 48% were male. 83% were in-house referrals and 17% were outside referrals. 56 % of the studies performed had a recording duration < 48 hours, the remainder were >48 hours (see Figure 1 for summary). 39 studies were performed to characterize spells; the patient's habitual event(s) were captured in 51.3%, but only 15% of those were associated with ictal EEG correlates (see Figure 2). 6 aEEG studies were performed for quantification of seizures and IEDs; findings on these permitted weaning, continuing, or starting an anti-seizure medication or confirming suppression of electrical status epilepticus of sleep (ESES). aEEG study was performed in one patient undergoing epilepsy surgery evaluation in whom no seizures occurred during one week of inpatient monitoring. Focal seizures with ictal correlates were captured by the aEEG. Conclusions: Outpatient aEEG is under-utilized at our institution and only recently has become an alternative to the EMU. Physicians are more likely to refer those with nonepileptic spells to aEEG than to the EMU. However, in the absence of video or a good clinical description, events without EEG correlation can only offer a presumptive diagnosis of nonepileptic spells. aEEG without video is a useful adjunct for confirming and localizing epileptic seizures and IEDs in the home setting in patients already diagnosed with epilepsy and whose seizures are associated with ictal EEG correlates. The addition of video to the outpatient setting will surely add to the diagnostic yield.