PURPOSE Patients with a first unprovoked epileptic seizure are often seen in emergency services. Electroencephalography (EEG) is indicated for diagnosing epilepsy, but the optimal time to perform this test has not been defined. This study aimed to determine the time interval following a seizure within which EEG has the greatest diagnostic yield. METHODS We conducted a retrospective study of all adult patients with a first unprovoked seizure who had undergone emergency EEG (July 2014-December 2019). Data collection included demographics, seizure type, time interval to EEG study, EEG pattern identified, and the prescription after emergency assessment. An optimal cut-off point for time to EEG was obtained, and an adjusted regression model was performed to establish associations with the presence of epileptiform abnormalities. RESULTS A total of 170 patients were included (mean age: 50.7 years, 40.6% women). Epileptiform discharges were identified in 34.1% of recordings, nonepileptiform abnormalities in 46.5%, and normal findings in 19.4%. A lower latency from seizure to EEG was associated with a higher probability of finding epileptiform discharges (median: 12.7 in the epileptiform EEGs vs. 20 h in the nonepileptiform EEGs, p < 0.001). The time interval associated with the highest probability of detecting an epileptiform EEG pattern was within the first 16 h after seizure onset: 52.1% of recordings performed before the 16-h cut-off showed these abnormal patterns compared with 20.2% performed after (p < 0.001). These findings were not related to the presence of an epileptogenic lesion in neuroimaging or to other clinical variables. The finding of epileptiform abnormalities was followed by a greater prescription of antiseizure drugs (96.4% vs. 66% in nonepileptiform patterns, p < 0.001). CONCLUSION The diagnostic yield of EEG following a first unprovoked epileptic seizure is highest when this test is performed within the first 16 h after onset of the event.

中文翻译：

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第一次癫痫发作后应多长时间进行紧急脑电图检查？

目的 首次无端癫痫发作的患者经常出现在急诊室。脑电图 (EEG) 可用于诊断癫痫，但尚未确定进行此测试的最佳时间。本研究旨在确定癫痫发作后脑电图具有最大诊断率的时间间隔。方法 我们对所有接受过紧急 EEG 的首次无端癫痫发作的成年患者（2014 年 7 月至 2019 年 12 月）进行了一项回顾性研究。数据收集包括人口统计学、癫痫发作类型、EEG 研究的时间间隔、确定的 EEG 模式以及紧急评估后的处方。获得了 EEG 时间的最佳截止点，并进行了调整后的回归模型以建立与癫痫样异常存在的关联。结果 共纳入 170 名患者（平均年龄：50.7 岁，40.6% 为女性）。在 34.1% 的录音中发现癫痫样放电，46.5% 为非癫痫样异常，19.4% 为正常发现。从癫痫发作到 EEG 的潜伏期越短，发现癫痫样放电的可能性越大（中位数：癫痫样脑电图中的 12.7 小时与非癫痫样脑电图中的 20 小时，p < 0.001）。与检测癫痫样 EEG 模式的最高概率相关的时间间隔是在癫痫发作后的前 16 小时内：在 16 小时截止之前进行的记录中有 52.1% 显示这些异常模式，而在此之后进行的记录为 20.2% (p < 0.001）。这些发现与神经影像学中是否存在致癫痫病灶或其他临床变量无关。癫痫样异常的发现之后是更多的抗癫痫药物处方（96.4% vs. 66% 在非癫痫样模式中，p < 0.001）。结论 在事件发生后的前 16 小时内进行该测试时，首次无端癫痫发作后的 EEG 诊断率最高。