01954nas a2200169   4500000000100000008004100001260001700042100001900059700001600078700001500094245009800109250001500207300001100222490000800233520149700241020004601738       2012                            d  c2419116292021 aArima Hisatomi1 aFaulkner H.1 aMohamed A.00aLatency to first interictal epileptiform discharge in epilepsy with outpatient ambulatory EEG  a2012/05/25  a1732-50 v1233 a<p>
OBJECTIVE: The diagnosis and classification of epilepsy often relies upon the demonstration of interictal epileptiform discharges (IEDs). Routine 20-min EEG recording has low sensitivity, with multiple EEGs increasing sensitivity to a maximum of 77% (Doppelbauer et al., 1993). An alternate strategy is the use of prolonged continuous EEG; however, there are no data on the average latency to first IED with ambulatory monitoring. METHODS: In this retrospective study we reviewed 180 consecutive patients with epilepsy referred to a Specialist Epilepsy Unit who had undergone 96h outpatient ambulatory EEGs, without medication withdrawal, where IEDs were recorded. Latency to, and factors affecting first IED were analysed. RESULTS: Median latency to first IED was 316min, (interquartile range 70-772min, n=180). IEDs were recorded in 44% of patients within 4h, 58% within 8h, 85% within 24h and 95% within 48h. Recording for the full 96h period revealed only 5% further IEDs. Multivariate analysis showed the latencies to IEDs with generalised epilepsies were shorter than with focal epilepsies (p&lt;0.0001). CONCLUSIONS: In 95% of patients showing scalp IEDs a 48h recording was sufficient for electro-clinical classification in this study. SIGNIFICANCE: Our data are the first to show the latency to recording interictal epileptiform discharges with prolonged outpatient EEG monitoring. These data are important in guiding diagnostic practice in Specialist Epilepsy Services.
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