Unique place of ambulatory EEG (aEEG) in management of epilepsy

(a) evaluate yield of ambulatory EEG (aEEG) for capturing seizures/non-epileptic events (b) compare aEEG yield in capturing Inter-ictal Epileptiform Discharges (IEDs) (c) evaluate aEEG role for Anti-Seizure Drug (ASD) wean in patients who were seizure-free for ≥ 2 years preceding aEEG.

Retrospective chart review was performed for patients who underwent aEEG over a specified time frame of 1.5 years. "Events" were documented on a log. Variables collected: age, sex, indication for test, seizure frequency, ASDs, aEEG & previous rEEG findings, etc. Follow-up clinic notes were reviewed to document impact of aEEG findings.

309 patients were included: (a) Electrographic seizures captured in 10 (3 %, only 2/10 (20 %) were reported on log), 14 had non-epileptic events vs only 1 electrographic seizure on rEEG and no non-epileptic events (b) aEEG yield for IEDs was 29 % (88/309). Of 88 patients with aEEG, 59 also had also ≥ 1 prior rEEGs and only 34/59 captured IEDs indicating higher yield of aEEG for IEDs. 25 patients had a normal rEEG who then had IEDs on aEEG (c) aEEG was ordered for ASD wean in 22.

seizures 2 (9 %), rare focal IEDs 4 (18 %), frequent focal/generalized IEDs 1 each, 14 nonepileptiform aEEG. ASDs were not withdrawn in patients with seizures & frequent IEDs. Of 4 with rare IEDs, 2 (50 %) had seizure recurrence after wean, 2 underwent successful (seizure-free > 1 year) wean. Of 14 with nonepileptiform EEG, 3 (21 %) had recurrence after wean & 11underwent successful wean.

Patients with epilepsy underestimate seizure burden. Clinical decision-making just based on verbal report can be misleading. aEEG may help provide estimation of unrecognized seizures and help guide ASD wean decision.