Sleep but not hyperventilation increases the sensitivity of the EEG in patients with temporal lobe epilepsy

Purpose: To evaluate the relative impact of 3 and 5min of hyperventilation (HV) and different sleep stages on the sensitivity of the interictal EEG in focal epilepsy. Methods: We examined 20 patients with temporal lobe epilepsy (TLE, 85%) or extratemporal epilepsy during EEG-monitoring. We compared 6min EEG (12 epochs of 30s) during/after each: (a) waking; (b) 5 or 3min of HV; (c) sleep stages 1, 2, 3/4 and REM regarding the frequency of epileptiform discharges (ED). The Wilcoxon matched pairs signed rank test was used. The main endpoint was the comparison of 5min of HV with sleep stage 2. Results: During sleep stage 2, ED were more frequent than during/after 5min of HV (P=0.002). Compared to the waking EEG, all NREM-sleep stages activated ED. Sleep stage 2 was associated with the strongest activation. There was no difference between the waking state and REM-sleep. Compared to the waking EEG, neither 3 nor 5min of HV showed an activation of ED. Conclusion: In patients with TLE, sleep stage 2 shows a significantly higher sensitivity for ED than 5min of HV. Compared to the waking EEG, HV showed no activating effect on ED. These results suggest that in patients with the clinical diagnosis of TLE (and possibly other focal epilepsies) measures to record sleep stage 2 (such as sleep deprivation) should be increased whereas HV appears to be dispensable in this setting.