Epilepsy & Behavior 44 (2015) 260
Contents lists available at ScienceDirect
Epilepsy & Behavior journal homepage: www.elsevier.com/locate/yebeh
Letter to the Editor Reply to the Letter to the Editor ‘“Chapeau de gendarme”: A fronto-mesial ictal sign?’ by Leitinger et al.
To the Editor We thank the Editor for the opportunity to reply to the challenging case reported by Leitinger et al. As we recently reported that the “chapeau de gendarme” (CG) sign was suggestive of anterior cingulate gyrus (ACG) involvement in frontal lobe epilepsy [1], they discuss the significance of this peculiar facial expression in a patient investigated with intracranial electrodes in whom they did not record any discharge affecting the ACG during CG occurrence. It is always very difficult to analyze intracranial recordings without any knowledge of the electroclinical hypotheses and depth electrode location scheme. However, given the provided data, it can be assumed that the main hypothesis was the right central region. Because no discharge was recorded within the ACG while CG was observed, the authors conclude that this sign could be generated by other brain areas. They are unfortunately not able to propose any localization since ictal clinical symptoms occurred many seconds before EEG changes. This situation represents an insufficient sampling that did not allow defining the epileptogenic or symptomatogenic zones. This reflects both the difficulties and limitations of the SEEG methodology based on precise anatomical and electroclinical correlations. As the patient had an emotional expression with staring and CG as early ictal features, it is difficult to understand why the anterior part of the frontal lobe was not covered by electrodes. In addition, there is only one electrode on the left side, but we have no data that allow focusing on the right side. Finally, although the placement of frontal electrodes is indicated on the
http://dx.doi.org/10.1016/j.yebeh.2014.12.038 1525-5050/© 2014 Elsevier Inc. All rights reserved.
sagittal MRI slices, the exact location of each electrode must be demonstrated by the postimplantation coregistration and reconstruction of their trajectory within the brain structures. This is the only way to be certain that the targeted structure is reached instead of adjacent gray or white matter and, thus, to avoid misinterpretations. Given these limitations, we think that this observation does not sufficiently into question our data that were established from a series of patients in whom the epileptogenic zone could be identified unequivocally and in whom the cure of epilepsy resulted from surgery, thereby validating the relevance of our hypotheses. Nevertheless, we did not say that the ACG was the only region likely to produce CG. We only have drawn the attention of clinicians about its value in frontal lobe seizures. Furthermore, we have emphasized the importance of the involvement of a network also implicating the insula. We remain available to discuss more thoroughly this case with all clinical and electrophysiological data. Conflict of interest The author has no conflicts of interest to declare. Reference [1] Souirti Z, Landré E, Mellerio C, Devaux B, Chassoux F. Neural network underlying ictal pouting (“chapeau de gendarme”) in frontal lobe epilepsy. Epilepsy Behav 2014;37: 249–57.
Francine Chassoux Epilepsy Unit, Sainte-Anne Hospital, 1 rue Cabanis, 75014 Paris, France E-mail address: [email protected]. 24 December 2014
Contents lists available at ScienceDirect
Epilepsy & Behavior journal homepage: www.elsevier.com/locate/yebeh
Letter to the Editor Reply to the Letter to the Editor ‘“Chapeau de gendarme”: A fronto-mesial ictal sign?’ by Leitinger et al.
To the Editor We thank the Editor for the opportunity to reply to the challenging case reported by Leitinger et al. As we recently reported that the “chapeau de gendarme” (CG) sign was suggestive of anterior cingulate gyrus (ACG) involvement in frontal lobe epilepsy [1], they discuss the significance of this peculiar facial expression in a patient investigated with intracranial electrodes in whom they did not record any discharge affecting the ACG during CG occurrence. It is always very difficult to analyze intracranial recordings without any knowledge of the electroclinical hypotheses and depth electrode location scheme. However, given the provided data, it can be assumed that the main hypothesis was the right central region. Because no discharge was recorded within the ACG while CG was observed, the authors conclude that this sign could be generated by other brain areas. They are unfortunately not able to propose any localization since ictal clinical symptoms occurred many seconds before EEG changes. This situation represents an insufficient sampling that did not allow defining the epileptogenic or symptomatogenic zones. This reflects both the difficulties and limitations of the SEEG methodology based on precise anatomical and electroclinical correlations. As the patient had an emotional expression with staring and CG as early ictal features, it is difficult to understand why the anterior part of the frontal lobe was not covered by electrodes. In addition, there is only one electrode on the left side, but we have no data that allow focusing on the right side. Finally, although the placement of frontal electrodes is indicated on the
http://dx.doi.org/10.1016/j.yebeh.2014.12.038 1525-5050/© 2014 Elsevier Inc. All rights reserved.
sagittal MRI slices, the exact location of each electrode must be demonstrated by the postimplantation coregistration and reconstruction of their trajectory within the brain structures. This is the only way to be certain that the targeted structure is reached instead of adjacent gray or white matter and, thus, to avoid misinterpretations. Given these limitations, we think that this observation does not sufficiently into question our data that were established from a series of patients in whom the epileptogenic zone could be identified unequivocally and in whom the cure of epilepsy resulted from surgery, thereby validating the relevance of our hypotheses. Nevertheless, we did not say that the ACG was the only region likely to produce CG. We only have drawn the attention of clinicians about its value in frontal lobe seizures. Furthermore, we have emphasized the importance of the involvement of a network also implicating the insula. We remain available to discuss more thoroughly this case with all clinical and electrophysiological data. Conflict of interest The author has no conflicts of interest to declare. Reference [1] Souirti Z, Landré E, Mellerio C, Devaux B, Chassoux F. Neural network underlying ictal pouting (“chapeau de gendarme”) in frontal lobe epilepsy. Epilepsy Behav 2014;37: 249–57.
Francine Chassoux Epilepsy Unit, Sainte-Anne Hospital, 1 rue Cabanis, 75014 Paris, France E-mail address: [email protected]. 24 December 2014
