T71. 24-Hour video EEG in the evaluation of the first unprovoked seizure

Introduction In subjects with epilepsy, the sensitivity to detect epileptiform discharges in EEG recordings increases with the duration of the recording. Whether this rule applies also to EEGs performed for the assessment of a first unprovoked seizure is not clear yet. The optimal EEG duration in this scenario is not known, although this test is crucial in quantifying the risk of seizure recurrence in the absence of abnormalities on neurological examination or neuroimaging studies. At our center, some patients with a first seizure underwent 24-h video EEG (VEEG) monitoring at the request of their neurologists. Methods We retrospectively identified patients who underwent 24-h VEEG with “first seizure” as an indication. We excluded subjects with obvious abnormalities on neurological examination or neuroimaging studies. In addition to demographic and disease related variables, we noted the presence or absence of epileptiform discharges in the VEEG study, the latency for the appearance of such discharges, their distribution, and the behavioral state they appear in. Other less specific EEG abnormalities were also tabulated. Results We identified 11 such patients (six women, five men) between May 2016 and November 2017, with an age range of 15–50. They had all experienced a first unprovoked seizure of the generalized tonic-clonic type by description; eight during wakefulness. The VEEG was performed two days to six months after the seizure. Four studies showed focal epileptiform discharges; two exhibited interictal epileptiform abnormalities (right frontal spike/wave and left fronto-temporal sharp waves) within 15 min from the start of the recording (the routine EEG few months earlier was normal for one of them), while the other two recorded actual subtle seizures (one case had two left fronto-temporal subtle seizures 18 h into the recording, during sleep, without earlier interictal discharges, another case had a subtle left temporal seizure during wakefulness three hours into the recording, followed by the activation of left temporal sharp waves). Two additional patients exhibited less specific EEG abnormalities, in the form of focal or generalized slowing. The remaining five studies were normal. Conclusion This pilot experience is too small to adequately assess the value of 24-h VEEG in the evaluation of the first seizure, but in at least two of the 11 patients the epileptiform discharges occurred many hours into the recording and would have been missed in a shorter routine EEG. Another patient had an initial normal routine EEG, but the abnormality appeared within minutes in the following VEEG study, implying that a second routine EEG instead would have probably been equally diagnostic. The four patients with ictal and interictal epileptiform discharges were subsequently started on anti-seizure medications, based mainly on the VEEG information. A larger study is needed to answer the question about the optimal duration of EEG recordings in the context of a first seizure.