Resection Of Amygdala Research Articles

Temporal lobectomy evidence for the role of the amygdala in early emotional face and body processing.

The amygdala is believed to make invaluable contributions to visual emotion processing. Yet how this subcortical body contributes to emotion perception across time is contended. Here, we measured differences in the perceptual processing of emotional stimuli after unilateral temporal lobe and amygdala resection (TLR) in humans, using EEG. Through mass univariate analysis of brain activity, we compared responses to fearful and neutral faces (left TLR N = 8, right TLR N = 8, control N = 8), and fearful and neutral bodies (left TLR N = 9, right TLR N = 9, control N = 9). We found that TLR impaired the early-stage perceptual processing of emotional stimuli seen in the control group. Indeed, in controls a heightened responses to fearful faces was found in the 140-170 ms time window, over temporo-parietal electrodes. This effect was also present in the left TLR group but disappeared in the right TLR group. For emotional bodies, brain activity was differentially sensitive to fearful stimuli at 90-120 ms in the control group, but this effect was eliminated in both TLR groups. Collectively, these results reveal the amygdala contributes to the early stages of perceptual processing that discriminate emotional stimuli from neutral stimuli. Further, they emphasize the unique role of the right medial temporal structures such as the amygdala in emotional face perception.Significance Statement This research is the first case to date to measure the electrophysiological correlates of emotional expressions represented by bodies after medial temporal resection as compared to healthy controls. It is also the first instance of the use of mass univariate analysis to assess EEG data to emotional content after TLR. This work sheds light on the potential impact of medial temporal lobe resection on early affective visual stimuli processing. Importantly, this research also indicates the integral role that resected regions like the amygdala play in early affective processing of human forms.

Chronologic Changes in Transcranial Motor Evoked Potential During Anterior Temporal Lobectomy in Patients with Temporal Lobe Epilepsy: A Single-Center Cross-Sectional Analytic Study

Despite the benefits of anterior temporal lobectomy with amygdalohippocampectomy in patients with temporal lobe epilepsy (TLE), approximately up to 5% may have hemiparesis as its postoperative complication. This paper aims to describe which step/s of the anterior temporal lobectomy with amygdalohippocampectomy have the highest probability of having the greatest decrease in motor evoked potential (MEP) amplitude. This study used a cross-sectional design of obtaining data from TLE patients who underwent anterior temporal lobectomy with amygdalohippocampectomy with transcranial MEP monitoring. Each of the following steps were evaluated for reduction in MEP amplitude: 1) dural opening, 2) opening the inferior horn, 2) vertical temporal lobe resection 3) subpial dissection, 4) temporal lobe stem resection, 5) lateral temporal lobe resection, 6) hippocampal resection, 7) amygdala resection, 8) uncus resection, and 9) dural closure. Nineteen patients were included in the study. Based on the Friedman Test, 1 or more steps had significantly different average MEP amplitude reductions (Friedman= 50.7, P= 0.0001). When compared with baseline (100%, cutoff P= 0.005), hippocampal resection (z= -3.81, P < 0.0001), T1 subpial dissection (z= -3.2, P= 0.0010), uncus resection (z= -3.48, P= 0.0002), temporal stem resection (z= -3.26, P= 0.001), lateral temporal lobe resection (z= -3.13, P= 0.002), and amygdalectomy (-z= -3.37, P= 0.0005) were significantly lower. Of these, hippocampal resection, uncus resection, and amygdalectomy were deemed highly significant. MEP amplitude tends to decrease during amygdala, hippocampal, and uncal resection because of surgical manipulation of anterior choroidal arteries, which can potentially cause hemiparesis. Careful attention should be paid to changes in MEP during these steps.

Amygdala lesions are associated with improved mood after epilepsy surgery.

Neuroimaging studies in healthy and clinical populations strongly associate the amygdala with emotion, especially negative emotions. The consequences of surgical resection of the amygdala on mood are not well characterized. We tested the hypothesis that amygdala resection would result in mood improvement. In this study, we evaluated a cohort of 52 individuals with medial temporal lobectomy for intractable epilepsy who had resections variably involving the amygdala. All individuals achieved good post-surgical seizure control and had pre- and post-surgery mood assessment with the Beck Depression Inventory (BDI) ratings. We manually segmented the surgical resection cavities and performed multivariate lesion-symptom mapping of change in BDI. Our results showed a significant improvement in average mood ratings from pre- to post-surgery across all patients. In partial support of our hypothesis, resection of the right amygdala was significantly associated with mood improvement (r = 0.5, p = 0.008). The lesion-symptom map also showed that resection of the right hippocampus and para-hippocampal gyrus was associated with worsened post-surgical mood. Future studies could evaluate this finding prospectively in larger samples while including other neuropsychological outcome measures.

Early Epilepsy Surgery in Benign Cerebral Tumors: Avoid Your 'Low-Grade' Becoming a 'Long-Term' Epilepsy-Associated Tumor.

Epilepsy surgery in low-grade epilepsy-associated neuroepithelial tumors (LEAT) is usually evaluated in drug-resistant cases, often meaning a time delay from diagnosis to surgery. To identify factors predicting good postoperative seizure control and neuropsychological outcome, the cohort of LEAT patients treated with resective epilepsy surgery at the Epilepsy Center Frankfurt Rhine-Main, Germany between 2015 and 2020 was analyzed. Thirty-five patients (19 males (54.3%) and 16 females, aged 4 to 40 years (M = 18.1), mean follow-up 33 months) were included. Following surgery, 77.1% of patients remained seizure-free (Engel IA/ILAE 1). Hippocampus and amygdala resection was predictive for seizure freedom in temporal lobe epilepsy. In total, 65.7% of all patients showed cognitive deficits during presurgical workup, decreasing to 51.4% after surgery, predominantly due to significantly less impaired memory functions (p = 0.011). Patients with presurgical cognitive deficits showed a tendency toward a longer duration of epilepsy (p = 0.050). Focal to bilateral tonic-clonic seizures (p = 0.019) and young age at onset (p = 0.018) were associated with a higher likelihood of cognitive deficits after surgery. Therefore, we advocate early epilepsy surgery without requiring proof of drug-resistance. This refers especially to lesions associated with the non-eloquent cortex.

Technical challenges to anterior temporal lobectomy after laser interstitial thermal therapy for mesial temporal lobe epilepsy: technical note.

Mesial temporal sclerosis (MTS) is a frequent cause of medically refractory epilepsy, for which laser interstitial thermal therapy (LITT) is an effective treatment. However, experience with the technical considerations posed by additional surgery after an initial LITT procedure is lacking. The authors present the case of a 12-year-old female with medically refractory temporal lobe epilepsy and left MTS who underwent LITT at a separate institution prior to referral. This patient had no change in early postoperative seizure control (Engel class IVB) and then her seizures worsened despite ongoing medical treatment (Engel class IVC). Post-LITT MRI revealed sparing of the mesial hippocampus head, a poor prognostic factor. The authors describe the technical details illustrated by this case of secondary, stereotactic electroencephalography-guided mesial temporal resection following LITT. The case was managed with anterior temporal lobectomy including the resection of residual hippocampus and amygdala.

Optic Tract as an Upper Limit in Amygdalectomy: Microsurgical Study.

In surgeries involving resection of the amygdala, despite clear relations established with the medial, lateral, anterior, posterior, and inferior segments, the upper limit remains controversial. The optic tract (OT) has been anatomically considered as a good landmark immediately inferior to the striatopallidal region. This anatomic structure has barely been explored by microsurgical study, generating uncertainty about the exact relationship with the surrounding structures. To describe the OT in its entire length through microsurgical study, showing its superior, inferior, medial, and lateral relationships and highlighting its value as a landmark in superior amygdala resection. Microsurgical anatomic dissection of the OT, from its origin in the chiasm to the lateral geniculate nucleus was performed in 8 alcohol-fixed human hemispheres, showing its different segments and relations. Photographs were taken from different angles to facilitate surgical orientation. We performed a dissection of the OT, showing its position relative to caudate and hippocampal formations. We exposed the structures related to the OT superiorly (striatopallidal region and superior caudate fasciculus), inferiorly (head of the hippocampus, amygdala, anterior choroidal artery, perforating artery branch of the anterior choroidal artery, terminal stria, and basal vein), medially (internal capsule and midbrain), and laterally (temporal stem [uncinate and inferior fronto-occipital fascicle], anterior perforated substance, and superior caudate fasciculus). To date, there is a paucity of articles describing the anatomy of the OT from a neurosurgery perspective. In this study, we describe the microsurgical anatomic path of the OT, as a reliable upper limit landmark for amygdala resection.

Rapid processing of fearful faces relies on the right amygdala: evidence from individuals undergoing unilateral temporal lobectomy

Facial expressions of emotions have been shown to modulate early ERP components, in particular the N170. The underlying anatomical structure producing these early effects are unclear. In this study, we examined the N170 enhancement for fearful expressions in healthy controls as well as epileptic patients after unilateral left or right amygdala resection. We observed a greater N170 for fearful faces in healthy participants as well as in individuals with left amygdala resections. By contrast, the effect was not observed in patients who had undergone surgery in which the right amygdala had been removed. This result demonstrates that the amygdala produces an early brain response to fearful faces. This early response relies specifically on the right amygdala and occurs at around 170 ms. It is likely that such increases are due to a heightened response of the extrastriate cortex that occurs through rapid amygdalofugal projections to the visual areas.

Surgical outcomes of temporal lobe epilepsy in children

Objective To explore the surgical treatment and outcomes of temporal lobe epilepsy in children. Methods A retrospective analysis was conducted on 21 children with temporal lobe epilepsy admitted to Department of Neurosurgery, Children's Hospital Affiliated to Capital Institute of Pediatrics from September 2016 to June 2018. Individualized surgical treatment plan was formulated according to the semeiology, imaging and electroneurophysiological findings of the children. Standard anterior temporal lobectomy was undergone in 13 cases, enlarged resection of temporal lobe lesion in 3, selective hippocampal amygdala resection in 2, simple resection of medial temporal lobe lesion in 1, vascular malformation resection in 1, and anterior temporal lobe resection plus frontal lobe nodule resection in 1. All patients were followed up clinically after operation. The follow-up included cranial MRI, electroencephalogram and Engle rating. Results All 21 patients underwent successful operation. No serious complications occurred after surgery. The pathological results were mixed neuronal-glial tumor in 14 cases, pleomorphic xanthoastrocytoma in 1, hippocampal sclerosis in 3, focal cortical dysplasia IIb in 1, tuberous sclerosis in 1, and cerebral arteriovenous malformation in 1. The follow-up duration of 21 patients was 18.0±5.9 months (9-30 months). A review of head MRI showed that all tumors were completely resected and no recurrence was seen of the patients with tumor. A review of the EEG showed that there was still a large amount of epileptic discharges in the temporal lobe of 1 patient, and the epileptic discharges of the remaining 20 cases were significantly reduced or disappeared compared with preoperative conditions. Eighteen patients were followed up for more than 12 months. Up to the last follow-up, 17 cases were classified as Engle Ⅰ and 1 as Engle Ⅳ. Conclusion Individualized surgical procedures based on comprehensive assessment of the semeiology, imaging and electroneurophysiology of children with temporal lobe epilepsy could lead to good outcomes. Key words: Epilepsy; Temporal lobe; Child; Neurosurgical procedures; Treatment outcome

The epileptogenic zone in pharmaco-resistant temporal lobe epilepsy with amygdala enlargement.

Temporal lobe epilepsy with amygdala enlargement (TLE-AE) has been considered a subtype of TLE. We evaluated the epileptogenic zone in patients with TLE-AE, who underwent intracranial video-EEG (ivEEG) and/or intraoperative electrocorticography (ioECoG) as well as epilepsy surgery. Eleven patients with TLE-AE were enrolled and investigated based on seizure profile, volumetric MRI, the Wechsler Memory Scale-Revised (WMS-R), the location of seizure onset zone (SOZ) and irritative zone (IZ) based on ivEEG (n=8), the location of interictal epileptiform discharges (IEDs) based on ioECoG (11), surgical procedure, and seizure outcome. The mean age at seizure onset was 34.9 years (range: 23-57). The mean duration of seizures was 5.0 years (range: 1-10). The number of AEDs was 2.3 (range: 1-5). The mean seizure frequency was nine per month (range: 1-30/month). All patients presented with focal impaired awareness seizures with (n=9) and without (2) secondary generalized convulsions. Volumetric MRI analysis showed unilateral enlarged amygdala with statistical significance (p<0.01). None of the patients' hippocampi had any abnormality based on MRI. Pre-operative mean verbal, visual, and delayed recall scores based on the WMS-R were over 100. The SOZ and IZ were identified in both the amygdala and hippocampus in seven patients and in only the amygdala in one patient based on ivEEG. IEDs were identified in the hippocampus in six patients and in both the amygdala and hippocampus in four patients based on ioECoG. All 11 patients underwent anterior temporal lobectomy, including amygdala resection, with multiple hippocampal transections (dominant hemisphere: seven patients) and resection (non-dominant hemisphere: three patients). Nine (81.8%) of 11 patients achieved seizure freedom with a mean follow-up of 26 months (range: 12-47). Post-operative WMS-R results did not show any significant deterioration, with a mean follow-up of 15 months (range: 12-24). The resected amygdala showed no histopathological abnormality. The epileptogenic zone of TLE-AE involves both the amygdala and hippocampus. ivEEG may be needed to explore the SOZ in normal hippocampus in addition to enlarged amygdala. Amygdala resection and multiple hippocampal transections may control the epileptogenic limbic system and save memory function in patients with TLE-AE.

Effect of Extent of Hippocampal and Amygdala Resection on Seizure Outcome in Patients with Refractory Epilepsy Secondary to Medial Temporal Sclerosis

Effect of Extent of Hippocampal and Amygdala Resection on Seizure Outcome in Patients with Refractory Epilepsy Secondary to Medial Temporal Sclerosis

Role of mesial temporal lobe structures in sensory processing in humans: a prepulse modulation study in temporal lobe epilepsy.

Prepulse modulation (PPM) is an electrophysiological method which enables to assess sensory processing in vivo. Reflex responses may be facilitated or inhibited (prepulse inhibition, PPI) after a weak stimulus. Theoretically, in animal studies, the generator of PPI involves pedunculopontine nucleus which is modulated by various structures, including amygdala. We aimed to investigate whether or not there was a role of limbic structures in the generation of PPM in humans. For this purpose, we studied PPM of the blink reflex (BR) in 10 patients with mesial temporal lobe epilepsy (MTLE group) and in nine patients who had previously undergone amygdala resection for medically resistant MTLE (surgery group). A control group including 19 healthy volunteers was formed. Blink reflex, BR-PPM and BR excitability recovery were recorded in all participants. Two components of BR, first early ipsilateral component (R1) and second late bilateral components (R2 and R2c) were identified. All BR parameters after single stimulation were normal in all groups. Compared to healthy subjects, R2-PPI was more pronounced in the surgery group whereas there was a R2-PPI deficit in the MTLE group. R2-PPI deficit in the MTLE group was more prominent on the lesion side. Ipsilesional R1 facilitation was more evident at ISI of 100ms in both MTLE and surgery groups compared to healthy subjects. BR excitability recovery was not different between groups. MTLE in humans leads to a PPI deficit. Interestingly, removal of amygdala in humans with MTLE probably provides more efficient functioning of PPI network. Amygdala and hippocampus play roles in the human R2-PPI circuit. Modulation of R1 facilitation is unilateral whereas the modulation of R2-PPI is bilateral, though asymmetric.

Conscious control of breathing: A key to prevention of sudden unexpected death in epilepsy?

Conscious control of breathing: A key to prevention of sudden unexpected death in epilepsy?

Fear-conditioned alterations of motor cortex excitability: The role of amygdala.

We hypothesized that fear-conditioning may increase motor cortical excitability in preparation for response to fear. We tested our hypothesis in healthy subjects and in the second step, to determine the role of amygdala in alterations of motor cortex excitability, we included a group of patients who previously underwent unilateral amygdalo-hippocampectomy for temporal lobe epilepsy. In the first step, we included 16 healthy volunteers. In the second step, 14 patients who previously underwent unilateral amygdalo-hippocampectomy for temporal lobe epilepsy and who were seizure-free were included in the study. Motor evoked potentials (MEPs) recorded over right hand were recorded twice before and after the observation of fearful faces (fear-conditioning). Auditory startle response (ASR) was also recorded. Comparisons of before and after fear-conditioning MEP parameters within the healthy subjects group showed MEP amplitude was higher after fear-conditioning (p=0.019). Same comparison in patients with unilateral amygdalo-hippocampectomy demonstrated shorter MEP latency (p=0.036) and higher MEP amplitudes after fear-conditioning (p=0.046). CSPs did not show any change after this paradigm in both groups. Comparisons of ASR findings before and after fear-conditioning demonstrated enhanced responses after fear-conditioning in both healthy subjects and in patients with unilateral amygdalo-hippocampectomy. For MEPs or ASRs, there was a similar enhancement in patients with left- or right-sided operation. Fear-potentiation of both corticospinal and reticulospinal pathways occurs in healthy humans and bilateral potentiation of ASR and potentiation of MEPs are maintained even after resection of unilateral amygdala regardless of its side.

Anterior Temporal Sulcus: A Reliable Intraoperative Landmark for Accurately Delineating the Superior Limit of Amygdala Resection during Anterior Temporal Lobectomy

Background: Reliable anatomical landmarks are essential to avoiding injuries to the optic tract, anterior choroidal artery and basal ganglia during anterior temporal lobectomy (ATL). We describe an anatomic landmark, specifically the anterior temporal sulcus (ATS), as a reliable method to define the anterior portion of the endorhinal sulcus and the superior limit of amygdala resection. Methods: A total of 25 consecutive patients undergoing ATL at Rush University Medical Center (RUMC) were identified, and their preoperative brain magnetic resonance imaging (MRI) studies were analyzed. Results: All patients underwent successful ATL without any complication. There was no injury to the optic tract, anterior choroidal artery or basal ganglia using ATS as the landmark for the superior limit of amygdala resection. The ATS was clearly identifiable on coronal preoperative MRI in 48 out of 50 temporal lobes (96%). The ATS was present in all 25 left temporal lobes (100%); 2 of the 25 right temporal lobes had absent ATS (8%). Following the ATS posteriorly on coronal MRI, it led to the endorhinal sulcus and accurately predicted the superior extent of amygdala resection in all 25 patients (48 temporal lobes). Conclusion: The ATS is a reliable anatomical landmark that accurately delineates the superior border of the amygdala during ATL.

Asymmetrical effects of unilateral right or left amygdala damage on auditory cortical processing of vocal emotions

We tested whether human amygdala lesions impair vocal processing in intact cortical networks. In two functional MRI experiments, patients with unilateral amygdala resection either listened to voices and nonvocal sounds or heard binaural vocalizations with attention directed toward or away from emotional information on one side. In experiment 1, all patients showed reduced activation to voices in the ipsilesional auditory cortex. In experiment 2, emotional voices evoked increased activity in both the auditory cortex and the intact amygdala for right-damaged patients, whereas no such effects were found for left-damaged amygdala patients. Furthermore, the left inferior frontal cortex was functionally connected with the intact amygdala in right-damaged patients, but only with homologous right frontal areas and not with the amygdala in left-damaged patients. Thus, unilateral amygdala damage leads to globally reduced ipsilesional cortical voice processing, but only left amygdala lesions are sufficient to suppress the enhanced auditory cortical processing of vocal emotions.

Chronic epilepsy due to low grade temporal lobe tumors and due to hippocampal sclerosis: Do they differ in post-surgical outcome?

Chronic seizures as a presenting feature of low grade temporal lobe gliomas and hippocampal sclerosis (HS) are reported to have similar outcomes although the prognostic indicators may not be the same. This study seeks to identify the variables that are associated with poor surgical outcome in both conditions. A retrospective analysis from our epilepsy data base was performed. All low-grade temporal lobe gliomas were selected and relevant variables were compared to the same variables in HS patients. There were 34 tumors (out of 233 cases of chronic temporal lobe epilepsy = 14.6 %) with a mean age of onset of 19 years, and the preoperative duration was 12.3 years. When compared to 120 HS patients both of these factors were significantly different (p < 0.001). Age at the time of surgery for tumors was 31.08 (p = 0.5). Tumors were left sided in 20 patients. In tumor cases amygdala resection was complete in 75 %, for hippocampus 24 % were complete and 39 % partial. Astrocytoma, ganglioglioma and oligodendroglioma constituted 80 % of tumor cases. Good outcome (Engel's Class I) was achieved in 88.2 % of tumor cases and 71 % of HS cases while poor outcome (Class III + IV) was seen in 5.9 and 16.7 % respectively. The follow up period for the two groups was not significantly different. In multivariate logistic regression analysis, the groups differed significantly in preoperative delay (between diagnosis and surgery) and in epilepsy outcome. Chronic temporal lobe epilepsy due to low-grade tumors had significantly better surgical outcome with considerably less preoperative delay. The age of onset of seizures was younger in HS patients but a delay in surgical treatment was significantly longer. Given that the diagnosis of treatment-resistant TLE secondary to HS can be established after two failed AED trials at optimal doses, shortening the interval between diagnosis and surgery may improve epilepsy outcome.

Enhanced Visual Cortical Activation for Emotional Stimuli is Preserved in Patients with Unilateral Amygdala Resection

Emotionally arousing pictures induce increased activation of visual pathways relative to emotionally neutral images. A predominant model for the preferential processing and attention to emotional stimuli posits that the amygdala modulates sensory pathways through its projections to visual cortices. However, recent behavioral studies have found intact perceptual facilitation of emotional stimuli in individuals with amygdala damage. To determine the importance of the amygdala to modulations in visual processing, we used functional magnetic resonance imaging to examine visual cortical blood oxygenation level-dependent (BOLD) signal in response to emotionally salient and neutral images in a sample of human patients with unilateral medial temporal lobe resection that included the amygdala. Adults with right (n = 13) or left (n = 5) medial temporal lobe resections were compared with demographically matched healthy control participants (n = 16). In the control participants, both aversive and erotic images produced robust BOLD signal increases in bilateral primary and secondary visual cortices relative to neutral images. Similarly, all patients with amygdala resections showed enhanced visual cortical activations to erotic images both ipsilateral and contralateral to the lesion site. All but one of the amygdala resection patients showed similar enhancements to aversive stimuli and there were no significant group differences in visual cortex BOLD responses in patients compared with controls for either aversive or erotic images. Our results indicate that neither the right nor left amygdala is necessary for the heightened visual cortex BOLD responses observed during emotional stimulus presentation. These data challenge an amygdalo-centric model of emotional modulation and suggest that non-amygdalar processes contribute to the emotional modulation of sensory pathways.

Relationship between post-operative depression/anxiety and hippocampal/amygdala volumes in temporal lobectomy for epilepsy

Patients with temporal lobe epilepsy (TLE) often present mood disturbances, which may either exacerbate or remit following surgery. The objective of the study was to investigate the relationship between post-operative depressive/anxiety symptoms and hippocampal/amygdala volumes following anterior temporal lobectomy. Thirty-five patients operated for TLE were assessed for mood disturbances by the Beck depression inventory (BDI) and Beck anxiety inventory (BAI). Post-operative MRI data were collected and volumetric analysis of the hippocampi (HV) and amygdala (AV) was performed. Correlations between volumetric data, measures of mood, and demographic and clinical data were calculated. BDI scores significantly correlated with the intact HV (p=0.029) as well as the absolute difference between the intact and remnant HV (p=0.021). This was evident in left-side resections (p=0.049); in right-side resections the correlation was marginally non- significant (p=0.057). Depressed patients also had smaller remnant AV (p=0.002). Furthermore, BAI was negatively correlated with the HV remnant in left-side resections (p=0.038). No other significant associations between post-operative mood disturbances and various demographic and clinical variables were observed. The severity of depressive symptomatology in operated epilepsy patients correlates with the extent of hippocampal and amygdala resection; this association appears to be more evident in left-side resections.

L’hémisphérotomie péri-insulaire : technique chirurgicale, monitoring EEG intraopératoire et résultats sur le contrôle de l’épilepsie

Peri-insular hemispherotomy is a surgical technique used in the treatment of drug-resistant epilepsy of hemispheric origin. It is based on the exposure of insula and semi-circular sulci, providing access to the lateral ventricle through a supra- and infra-insular window. From inside the ventricle, a parasagittal callosotomy is performed. The basal and medial portion of the frontal lobe is isolated. Projections to the anterior commissure are interrupted at the time of amygdala resection. The hippocampal tail and fimbria-fornix are disrupted posteriorly. We report our experience of 18 cases treated with this approach. More than half of them presented with congenital epilepsy. Neuronavigation was useful in precisely determining the center and extent of the craniotomy, as well as the direction of tractotomies and callosotomy, allowing minimal exposure and blood loss. Intra-operative monitoring by scalp EEG on the contralateral hemisphere was used to follow the progression of the number of interictal spikes during the disconnection procedure. Approximately 90% of patients were in Engel's Class I. We observed one case who presented with transient postoperative neurological deterioration probably due to CSF overdrainage and documented one case of incomplete disconnection in a patient presenting with hemimegalencephaly who needed a second operation. We observed a good correlation between a significant decrease in the number of spikes at the end of the procedure and seizure outcome. Peri-insular hemispherotomy provides a functional disconnection of the hemisphere with minimal resection of cerebral tissue. It is an efficient technique with a low complication rate. Intra-operative EEG monitoring might be used as a predictive factor of completeness of the disconnection and consequently, seizure outcome.

Is amygdala involved in early gaze processing? An electroencephalography study in epileptic patients with unilateral amygdala resection

Event Abstract Back to Event Is amygdala involved in early gaze processing? An electroencephalography study in epileptic patients with unilateral amygdala resection Laurence Conty1, 2*, M. Russo1, D. Dellacherie3, 4, S. Dupont4, M. Denos4, S. Samson3, 4 and N. George1, 2 1 CNRS-UPR640 LENA, France 2 Université Pierre et Marie Curie, Paris 6, France 3 Neuropsychologie et Cognition Auditive-JE 2497, Université Lille-Nord, France 4 Unité d’Epilepsie, Hôpital de la Pitié Salpêtrière, France Detecting the gaze direction of others is fundamental to adaptive interindividual behaviours. In particular, gaze contact appears as a crucial cue to reciprocal social attention and constitutes a frequent preliminary to interaction. In line with this view, several behavioural studies have shown that we are biased at detecting direct gaze as compared to other gaze directions [1]. Moreover, a growing number of studies show that the amygdala is involved in gaze processing, and particularly in processing gaze orientation [2]. This structure has also greater activity during the perception of direct, as compared to averted gaze [3]. This is congruent with the view that gaze contact is an intrinsically arousing stimulus. However, we do not have any information about the temporal involvement of the amygdala in gaze processing. More specifically, does it intervene at an early processing stage? Recently, our group examined the evoked potentials in human adults in response to the apparent motion of gaze [4]. The results showed that the subjects were faster to detect gaze moving toward them (direct gaze condition) as compared to gaze moving away from them (averted gaze condition). Moreover, the perception of direct relative to averted gaze evoked a strong enhancement of the N170 (around 160 ms over occipito-temporal sites), suggesting that gaze contact recruited more resources than averted gaze in the early stage of gaze direction processing. Direct and averted motion of gaze elicited also distinct ERP components between 160 and 210 ms over centro-parietal electrodes. Source reconstruction revealed the involvement of the Theory-of-Mind network, including the regions of the superior temporal sulcus, the medial prefrontal and the orbito-frontal cortices, in these two early dissociations. Nevertheless, the technique of source reconstruction is not ad-hoc to reveal the involvement of sub-cortical structures (such as amygdala). In order to investigate the hypothetic intervention of the amygdala in the early dissociations observed between direct and averted gaze, we used the same protocol by recording epileptic patients with unilateral amygdala resection as well as new control subjects matching with the patients in regard to their age, level of education and socio-professional situation. Currently, 10 patients and 6 control subjects have been processed. Preliminary results revealed that both our behavioural and early electrophysiological results were reproduced in patients and in control subjects. At first view, in epileptic patients, the result were reproduced whatever the side of the resection, in the right (3 subjects) or in the left (8 subjects) hemisphere. These preliminary results strongly suggest that the amygdala does not intervene at the early stage of gaze processing. Moreover, the amygdala does not appear to be necessary for speeding up the detection of direct gaze.