Spindle frequency activity may provide lateralizing information in drug-resistant nocturnal mesial frontal lobe epilepsy: A pilot study on the contribution of sleep recordings  Alessia Bersagliere, Peter Achermann, Giorgio Lo Russo, Paola Proserpio, Lino Nobili  Seizure - European Journal of Epilepsy  Volume 22, Issue 9, Pages 719-725 (November 2013) DOI: 10.1016/j.seizure.2013.05.011 Copyright © 2013 British Epilepsy Association Terms and Conditions

Fig. 1 Sleep EEG recording at seizure onset (patient 2). The seizure occurred during non-REM sleep stage 2. In this example, the pre-ictal signal was taken 18–13s before the onset of clinical manifestation (blue box). The ictal signal was taken 5 to 0s before the onset of clinical signs (red box). Note the increase in delta activity characterizing the last portion of the signal immediately preceding the hyperkinetic movements, which obscured the EEG recordings. Seizure - European Journal of Epilepsy 2013 22, 719-725DOI: (10.1016/j.seizure.2013.05.011) Copyright © 2013 British Epilepsy Association Terms and Conditions

Fig. 2 Topographic distribution of spectral power in non-REM sleep, during the pre-ictal and ictal phase. Average absolute power maps of four patients in the frequency range of delta activity (1–4Hz), and sigma activity (12–16Hz) are represented. Sleep maps were averaged across non-REM sleep epochs which did not contain seizure events (average of 38, 32, 22 and 30 20-s epochs of non-REM sleep, respectively), while preictal and ictal maps were averaged across 13, 24, 4 and 7 5-s epochs, respectively. Each row corresponds to one patient. Maps are based on 19 derivations (average reference; 10–20 system). Color coded power values are plotted at the corresponding position on the planar projection of the scalp model; the nose faces up. Values between electrodes were interpolated. To optimize contrast, each map was scaled separately; map maxima and minima (in μV2) are provided on the top right of each map. Seizure - European Journal of Epilepsy 2013 22, 719-725DOI: (10.1016/j.seizure.2013.05.011) Copyright © 2013 British Epilepsy Association Terms and Conditions

Fig. 3 LORETA source localization of delta activity (1–4Hz). The difference of activity between the ictal and pre-ictal phase is illustrated (squared magnitude of current density [μA2/mm4/Hz]). Each row represents average data from one patient. Left to right: frontal and top view of the brain, axial, sagittal and coronal cuts. The position of the maximum is indicated in the panels on the right, using arrows at the border of the cuts. The color scale was chosen to highlight the largest differences. The coordinates in MNI (Montreal Neurological Institute) space35 and the maximum value are given above the slices. The maximum of delta activity was found in the frontal lobe of all the subjects, consistent with power maps (Fig. 2A). The maximum was contralateral to the side of the epileptogenic zone in patients 2, 3 and 4, while it was ipsilateral in patient 1. Seizure - European Journal of Epilepsy 2013 22, 719-725DOI: (10.1016/j.seizure.2013.05.011) Copyright © 2013 British Epilepsy Association Terms and Conditions

Fig. 4 LORETA source localization of sigma activity (12–16Hz). The difference of activity in the ictal and pre-ictal phase is shown (squared magnitude of current density [μA2/mm4/Hz]). See Fig. 3 for details. The maximum of sigma activity was located in the frontal lobe (patients 1, 3 and 4) and in the parietal lobe (patient 2), consistent with the power maps (Fig. 2B). The maximum was ipsilateral to the side of the epileptogenic zone in all four patients. For details about the figure composition, see Fig. 3. Seizure - European Journal of Epilepsy 2013 22, 719-725DOI: (10.1016/j.seizure.2013.05.011) Copyright © 2013 British Epilepsy Association Terms and Conditions