Abstracts

Rationale: Afterhours EEG is increasingly utilized in hospital patients. While the detection of seizures and interictal epileptiform discharges (IEDs) has been shown to higher with pEEG than spot EEG, the relative value for particular indications can inform utilization. Methods: The Mayo EEG Report System was queried for prolonged and spot after hours EEGs performed between January 2015 and June 2015. 296 afterhours EEGs were identified, of which 140 were converted into pEEGs. Indications were categorized as: mental status changes, prior seizures rule out non-convulsive seizures, spells, and prognosis following anoxic brain injury.. Categorical data was analyzed using McNemar’s and Fisher’s exact tests; a p-value of 0.05 considered significant. Results: pEEG was superior to spot EEG for detection of IEDs and seizures (IEDs: 61  vs 48/140 (p=0.004) seizures: 29 vs 17/140 (p=0.012).  For the indication of evaluating for subclinical seizures following observed seizures, seizure detection was greater for pEEG than spot EEG (14/41 ( 34.1%) vs 4/41 (9.8%), p=0.002). There was no significant difference between these modalities for seizure detection in patients undergoing evaluation of spells or mental status changes without prior observed seizures. Detection of seizures on pEEG was higher for recordings greater than 24 hours (8/46, 17%, p=0.014) and 48 hours (19/26, 73%, p Conclusions: Increased value was demonstrated for afterhours pEEG over spot EEG in patients undergoing evaluation after observed clinical seizures and for coma. Afterhours spot EEG was noninferior to pEEG for indications of mental status changes without preceding seizure and spells for detection of seizures. Funding: N/A