The role of sleep electroencephalography in patients with new onset epilepsy

An increased propensity for seizures is associated with different stages of the sleep-wake cycle. In this study, we prospectively analyzed patients with new-onset epilepsy and investigated the clinical correlates of the yield obtained from sleep electroencephalography (EEG) recordings in patients with a normal wakefulness EEG.

All patients admitted to our epilepsy unit due to unprovoked epileptic seizures and not yet treated with antiepileptic drugs were recruited consecutively for the last three years. All had a routine EEG at wakefulness (WEEG), and those with no epileptiform activity had a video-EEG recording during sleep (SEEG).

We investigated a total of 241 patients; 129 patients (53.5%) had both wakefulness and sleep EEG recordings. The patients with abnormal WEEG were older than those with normal WEEG (p = 0.005). Abnormal WEEG was detected in only 31.2% of patients with focal seizures, but in 77.3% of patients with generalized seizures (p < 0.001). WEEG was abnormal in 44.0% of patients with diurnal seizures, but in 27.5% of nocturnal seizures (p = 0.007). Abnormal WEEG was present in 75.5% of patients with a presumed genetic origin and in 59.3% of patients with structural etiology (p < 0.001). Sleep EEG detected an abnormality in 41.8% of patients with normal WEEG; of these, 82.8% were focal abnormalities. In contrast, the majority of abnormalities detected in WEEG were generalized (55.8%, p < 0.001).

Our results showed a greater likelihood of abnormal WEEG in older patients and in those with generalized epilepsy, diurnally precipitating seizures, and epilepsy of presumed genetic origin.