Clinical Neurophysiology 127 (2016) 987–988
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Editorial
Ictal pattern on scalp EEG at onset of seizure in temporal lobe epilepsy: Old and new problems for epileptologists See Article, pages 1081–1087
Ictal scalp EEG findings in patients with temporal lobe epilepsy (TLE) form an important area of research for epileptologists. Since the importance of rhythmic theta activity in the temporal region for determining the lateralization of epileptic foci in TLE was first reported (Risinger et al., 1989), many investigations have examined this challenging topic. However, the details of these findings have not been fully clarified or fully related to the limitations of scalp EEG. In particular, the specific location of epileptic foci (such as the temporal lobe), the etiology (any associated pathology), and prediction of surgical outcome cannot be established based on the ictal EEG findings. Previous reports of ictal EEG findings in patients with TLE have been controversial (Table 1), as a result of the following confounding factors: Study design: seizure-based or patient-based study; Inclusion criteria of patients for each study: only medial TLE associated with hippocampal sclerosis or both medial and neocortical TLE; Analysis period: initial ictal period without/with subsequent development and propagation; and Experience and skill of the interpreting electroencephalographer: known to vary even among
board-certified electroencephalographers (Ebersole and Pacia, 1996; Lee et al., 2009; Pelliccia et al., 2013; Sirin et al., 2013; Vossler et al., 1998). In this issue of Clinical Neurophysiology, Malter et al. (2016) have demonstrated a notable finding that the ictal rhythmic pattern at seizure onset on scalp EEG increases in frequency with longer epilepsy duration. The authors investigated the predictive value of ictal scalp EEG in patients with unilateral mesial TLE caused by hippocampal sclerosis. However, neither rhythmic activity at seizure onset nor other scalp EEG features appeared to predict postsurgical seizure outcome. This study also demonstrated a close relationship between the frequency of ictal rhythmic activity and epilepsy duration, possibly due to timedependent changes in the epileptogenic networks. The findings of this study offer valuable insights into the clinical significance of rhythmic theta activity in the temporal region of ictal EEG onset. Further studies including patients with mesial TLE associated with causes other than hippocampal sclerosis and neocortical TLE will certainly increase the potential usefulness of ictal scalp EEG.
Table 1 Summary of previously reported studies of ictal EEG findings in patients with temporal lobe epilepsy. References
Ebersole and Pacia (1996) Vossler et al. (1998) Lee et al. (2009) Pelliccia et al. (2013) Sirin et al. (2013) Malter et al. (2016)
Etiology
Patients/seizures
Initial ictal discharge
Subsequent discharge development
Rhythmic alpha/theta
Rhythmic delta
Others
Rhythmic theta/ alpha
Rhythmic delta
Others
NA
NA
NA
NA
NA
NA
Various
93/NA
17 (18.3)/NA
53 (57.0)/NA
mTLEHS mTLEHS Various
63/328
40 (63.5)/NA
16 (25.4)/NA
23 (24.7)/ NA 7 (11.1)/NA
25/NA
9 (36)/NA
16 (64)/NA
0 (0)/NA
NA
NA
NA
NA/47
NA/0 (0)
NA/0 (0)
NA/47 (100)
NA/30 (63.8)
NA/10 (21.3)
42/152
NA/82 (53.9)
NA/49 (32.2)
NA/39 (57.4)
NA/22 (32.4)
63/219
NA/124 (56.6)
NA/95 (43.4)
NA/21 (13.8) NA/0 (0)
NA
NA
NA/7 (14.9) NA/7 (10.3) NA
mTLEHS mTLEHS
TLE, temporal lobe epilepsy; mTLE-HS, mesial TLE associated with hippocampal sclerosis; NA, not available.
http://dx.doi.org/10.1016/j.clinph.2015.07.023 1388-2457/Ó 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
988
Editorial / Clinical Neurophysiology 127 (2016) 987–988
Conflict of interest None of the authors has any conflict of interest to disclose. We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this editorial is consistent with those guidelines. References Ebersole JS, Pacia SV. Localization of temporal lobe foci by ictal EEG patterns. Epilepsia 1996;37:386–99. Lee EM, Im KC, Kim JH, Lee JK, Hong SH, No YJ, Lee SA, Kim JS, Kang JK. Relationship between hypometabolic patterns and ictal scalp EEG patterns in patients with unilateral hippocampal sclerosis: an FDG-PET study. Epilepsy Res 2009;84: 187–93. Malter MP, Bahrenberg C, Niehusmann P, Elger CE, Surges R. Features of scalp EEG in unilateral mesial temporal lobe epilepsy due to hippocampal sclerosis: determining factors and predictive value for epilepsy surgery. Clin Neurophysiol 2016;127:1081–7. Pelliccia V, Mai R, Francione S, Gozzo F, Sartori I, Nobili L, Lo Russo G, Pizzanelli C, Tassi L. Ictal EEG modifications in temporal lobe epilepsy. Epileptic Disord 2013;15:392–9.
Risinger MW, Engel Jr J, Van Ness PC, Henry TR, Crandall PH. Ictal localization of temporal lobe seizures with scalp/sphenoidal recordings. Neurology 1989;39: 1288–93. Sirin NG, Gurses C, Bebek N, Dirican A, Baykan B, Gokyigit A. A quadruple examination of ictal EEG patterns in mesial temporal lobe epilepsy with hippocampal sclerosis: onset, propagation, later significant pattern, and termination. J Clin Neurophysiol 2013;30:329–38. Vossler DG, Kraemer DL, Knowlton RC, Kjos BO, Rostad SW, Wyler AR, Haltiner AM, Hasegawa H, Wilkus RJ. Temporal ictal electroencephalographic frequency correlates with hippocampal atrophy and sclerosis. Ann Neurol 1998;43: 756–62.
Kazutaka Jin ⇑ Nobukazu Nakasato Department of Epileptology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan ⇑ Tel.: +81 22 717 7343; fax: +81 22 717 7346. E-mail address: [email protected] (N. Nakasato) Available online 14 August 2015
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Editorial
Ictal pattern on scalp EEG at onset of seizure in temporal lobe epilepsy: Old and new problems for epileptologists See Article, pages 1081–1087
Ictal scalp EEG findings in patients with temporal lobe epilepsy (TLE) form an important area of research for epileptologists. Since the importance of rhythmic theta activity in the temporal region for determining the lateralization of epileptic foci in TLE was first reported (Risinger et al., 1989), many investigations have examined this challenging topic. However, the details of these findings have not been fully clarified or fully related to the limitations of scalp EEG. In particular, the specific location of epileptic foci (such as the temporal lobe), the etiology (any associated pathology), and prediction of surgical outcome cannot be established based on the ictal EEG findings. Previous reports of ictal EEG findings in patients with TLE have been controversial (Table 1), as a result of the following confounding factors: Study design: seizure-based or patient-based study; Inclusion criteria of patients for each study: only medial TLE associated with hippocampal sclerosis or both medial and neocortical TLE; Analysis period: initial ictal period without/with subsequent development and propagation; and Experience and skill of the interpreting electroencephalographer: known to vary even among
board-certified electroencephalographers (Ebersole and Pacia, 1996; Lee et al., 2009; Pelliccia et al., 2013; Sirin et al., 2013; Vossler et al., 1998). In this issue of Clinical Neurophysiology, Malter et al. (2016) have demonstrated a notable finding that the ictal rhythmic pattern at seizure onset on scalp EEG increases in frequency with longer epilepsy duration. The authors investigated the predictive value of ictal scalp EEG in patients with unilateral mesial TLE caused by hippocampal sclerosis. However, neither rhythmic activity at seizure onset nor other scalp EEG features appeared to predict postsurgical seizure outcome. This study also demonstrated a close relationship between the frequency of ictal rhythmic activity and epilepsy duration, possibly due to timedependent changes in the epileptogenic networks. The findings of this study offer valuable insights into the clinical significance of rhythmic theta activity in the temporal region of ictal EEG onset. Further studies including patients with mesial TLE associated with causes other than hippocampal sclerosis and neocortical TLE will certainly increase the potential usefulness of ictal scalp EEG.
Table 1 Summary of previously reported studies of ictal EEG findings in patients with temporal lobe epilepsy. References
Ebersole and Pacia (1996) Vossler et al. (1998) Lee et al. (2009) Pelliccia et al. (2013) Sirin et al. (2013) Malter et al. (2016)
Etiology
Patients/seizures
Initial ictal discharge
Subsequent discharge development
Rhythmic alpha/theta
Rhythmic delta
Others
Rhythmic theta/ alpha
Rhythmic delta
Others
NA
NA
NA
NA
NA
NA
Various
93/NA
17 (18.3)/NA
53 (57.0)/NA
mTLEHS mTLEHS Various
63/328
40 (63.5)/NA
16 (25.4)/NA
23 (24.7)/ NA 7 (11.1)/NA
25/NA
9 (36)/NA
16 (64)/NA
0 (0)/NA
NA
NA
NA
NA/47
NA/0 (0)
NA/0 (0)
NA/47 (100)
NA/30 (63.8)
NA/10 (21.3)
42/152
NA/82 (53.9)
NA/49 (32.2)
NA/39 (57.4)
NA/22 (32.4)
63/219
NA/124 (56.6)
NA/95 (43.4)
NA/21 (13.8) NA/0 (0)
NA
NA
NA/7 (14.9) NA/7 (10.3) NA
mTLEHS mTLEHS
TLE, temporal lobe epilepsy; mTLE-HS, mesial TLE associated with hippocampal sclerosis; NA, not available.
http://dx.doi.org/10.1016/j.clinph.2015.07.023 1388-2457/Ó 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
988
Editorial / Clinical Neurophysiology 127 (2016) 987–988
Conflict of interest None of the authors has any conflict of interest to disclose. We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this editorial is consistent with those guidelines. References Ebersole JS, Pacia SV. Localization of temporal lobe foci by ictal EEG patterns. Epilepsia 1996;37:386–99. Lee EM, Im KC, Kim JH, Lee JK, Hong SH, No YJ, Lee SA, Kim JS, Kang JK. Relationship between hypometabolic patterns and ictal scalp EEG patterns in patients with unilateral hippocampal sclerosis: an FDG-PET study. Epilepsy Res 2009;84: 187–93. Malter MP, Bahrenberg C, Niehusmann P, Elger CE, Surges R. Features of scalp EEG in unilateral mesial temporal lobe epilepsy due to hippocampal sclerosis: determining factors and predictive value for epilepsy surgery. Clin Neurophysiol 2016;127:1081–7. Pelliccia V, Mai R, Francione S, Gozzo F, Sartori I, Nobili L, Lo Russo G, Pizzanelli C, Tassi L. Ictal EEG modifications in temporal lobe epilepsy. Epileptic Disord 2013;15:392–9.
Risinger MW, Engel Jr J, Van Ness PC, Henry TR, Crandall PH. Ictal localization of temporal lobe seizures with scalp/sphenoidal recordings. Neurology 1989;39: 1288–93. Sirin NG, Gurses C, Bebek N, Dirican A, Baykan B, Gokyigit A. A quadruple examination of ictal EEG patterns in mesial temporal lobe epilepsy with hippocampal sclerosis: onset, propagation, later significant pattern, and termination. J Clin Neurophysiol 2013;30:329–38. Vossler DG, Kraemer DL, Knowlton RC, Kjos BO, Rostad SW, Wyler AR, Haltiner AM, Hasegawa H, Wilkus RJ. Temporal ictal electroencephalographic frequency correlates with hippocampal atrophy and sclerosis. Ann Neurol 1998;43: 756–62.
Kazutaka Jin ⇑ Nobukazu Nakasato Department of Epileptology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan ⇑ Tel.: +81 22 717 7343; fax: +81 22 717 7346. E-mail address: [email protected] (N. Nakasato) Available online 14 August 2015
