Anterior Temporal Resection Research Articles

Distinct deficits of repetition priming following lateral versus anteromedial frontal cortex damage

Object repetition commonly leads to long-lasting improvements in identification speed and accuracy, a behavioral facilitation referred to as “repetition priming”. Neuroimaging and non-invasive electromagnetic stimulation studies have most often implicated the involvement of left lateral frontal cortex in repetition priming, although convergent evidence from neuropsychological studies is lacking. In the current study, we examine the impact of surgical resection for the treatment of epilepsy on the magnitude of repetition priming at relatively short-term (30–60 min delay) and long-term (3 months) delays in 41 patients with varying seizure foci and resection locations. Overall, patients exhibited significant repetition priming at both short-term and long-term delays. However, patients with frontal resections (largely anterior and medial frontal) differed significantly from those with right anterior temporal resections in showing fully intact short-term priming but absent long-term priming. In a comparison set of 10 recovered aphasic patients, patients with left lateral frontal damage exhibited impaired short-term priming relative to other frontal damage locations, suggesting the differential involvement of lateral and anteromedial frontal regions in mediating repetition priming at short-lag and long-lag timescales, respectively.

Cytokine profile in the peripheral blood and the brain in patients with focal drug-resistant epilepsy

Aim. To study markers of blood-brain barrier dysfunction (BBB) in patients with pharmacoresistant epilepsy (PhRE) – the amount of VEGF in endotheliocytes of brain capillaries, TNF-α in brain tissue and cytokine profile in blood serum.Materials and methods. The study included 30 patients with PhRE who underwent anterior temporal bloc resection. Histological samples of the brain were examined to assess the amount of VEGF and TNF-α; the concentration of cytokines in the blood serum was determined.Results. In the PhRE group, the densitometric density of cells expressing VEGF and the amount of TNF-α in the epileptogenic focus were higher than in the control groups (p < 0.001; p < 0.05). Compared with the control, the serum concentrations of IL-2 (0.98 ± 0.28 pg/ml vs. 2.80 ± 0.71 pg/ml; p < 0.001), IL-8 (14.04 ± 1.46 pg/ml vs. 26.13 ± 3.80 pg/ml; p < 0.001) and EGF (43.72 ± 5.63 pg/ml vs. 83.62 ± 24.06 pg/ml; p < 0.05) were statistically significantly lower in the PhRE group, and the amount of TNF-α (33.09 ± 1.23 pg/ml vs. 24.85 ± 1.32 pg/ml, p < 0.05), IL-4 (43.73 ± 2.57 pg/ml vs. 32.37 ± 5.80 pg/ml, p < 0.05), IL-5 (43.73 ± 2.57 pg/ml vs. 32.37 ± 5.80 pg/ml; p < 0.05), IL-7 (16.65 ± 3.07 pg/ml vs. 8.13 ± 1.67 pg/ml; p < 0.05), GRO (growth-regulated protein) (3054.0 ± 200.8 pg/ml vs. 1367.0 ± 187.3 pg/ml; p < 0.001), VEGF (316.10 ± 55.28 pg/ml vs. 95.22 ± 15.78 pg/ml; p < 0.01) are statistically significantly higher. There were no significant differences in the concentration of IL-1β, IL-1RA, IL-10 and IFN-γ between the PhRE group and the control.Conclusion. Based on the studied cytokine profile, there is no systemic inflammation in patients with PhRE. The established overexpression of VEGF in the brain and an increase in its concentration in the blood, combined with a decrease in serum EGF concentrations and an increase in GRO, as well as pro-inflammatory factors, indicates damage to the BBB. A high amount of TNF-α in the epileptic focus indicates neuroinflammation, and an increased concentration of this marker can be found in the blood of patients with BBB dysfunction.

Mapping connectivity fingerprints for presurgical evaluation of temporal lobe epilepsy

BackgroundSurgery may render temporal lobe epilepsy (TLE) patients seizure-free. However, TLE is a heterogenous entity and surgical prognosis varies between patients. Network-based biomarkers have been shown to be altered in TLE patients and hold promise for classifying TLE subtypes and improving pre-surgical prognosis. The aim of the present study is to investigate a network-based biomarker, the weighted degree of connectivity (wDC), on an individual level, and its relation to TLE subtypes and surgical prognosis.MethodsThirty unilateral TLE patients undergoing the same surgical procedure (anterior temporal resection) and 18 healthy controls were included. All patients were followed-up in the same center for a mean time of 6.85 years and classified as seizure-free (SF) and non seizure-free (non-SF). Using pre-surgical resting state functional MRI, whole brain wDC values for patients and controls were calculated. Then, we divided both temporal lobes in three Regions-of-interest (ROIs) -mesial, pole and lateral- as these areas are known to behave differently in seizure onset and propagation, delimiting different TLE profiles. The wDC values for the defined ROIs of each individual patient were compared with the healthy group.ResultsAfter surgery, 14 TLE patients remained SF. As a group, patients had higher wDC than controls in both the temporal pole (p < 0.05) as well as in the mesial regions (p < 0.002) of the to-be-resected temporal lobe. When comparing between SF and non-SF patients, a step-wise binary logistic regression model including all the ROIs, showed that having an increased wDC of the temporal pole (p < 0.05) and the mesial area (p < 0.05) of the to-be-resected temporal lobe was associated with seizure freedom long-term after surgery.ConclusionsThis study provides a network-based presurgical biomarker that could pave the way towards personalized prediction. In patients with TLE undergoing anterior temporal resections, having an increased wDC at rest could be a signature of the epileptogenic area, and could help identifying those patients who would benefit most from surgery.

A-250 Evidence for Language and Memory Improvements Following Right Anterior Temporal Lobectomy in a Patient with Mixed Language Dominance

Abstract Objective Anterior temporal lobectomy (ATL) surgery for epilepsy is commonly associated with post-surgical impairments in memory and language abilities, specifically episodic memory and confrontational naming. Less is known regarding outcomes of patients with atypical language dominance. Method Casey is a 19 year-old, ambidextrous, male with a history of remote symptomatic medically intractable focal epilepsy secondary to right inferior temporal encephalomalacia. Casey underwent right anterior temporal lobectomy and resection of mesial structures including part of the hippocampus. Results Casey’s pre-surgical neuropsychological evaluation revealed overall intellectual functioning in the average range with relative strengths in perceptual reasoning skills and weaknesses in attention, executive control, confrontational naming, and verbal fluency. Casey’s pre-surgical cognitive profile and functional MRI were suggestive of bilateral language organization. At post-surgical evaluation, Casey demonstrated strong overall cognitive abilities, basic reading, visual–spatial skills, and visual memory, as well as notable improvements in his processing speed and visual-motor integration. He demonstrated significant improvement in verbal working memory, verbal fluency, and contextual verbal memory. Casey continued to show significant weaknesses in word finding, phonetic verbal fluency, and rote verbal learning and memory, and milder weaknesses in aspects of executive functioning. Casey continued to demonstrate mood difficulties. Conclusions The current case provides evidence of continued mild deficits in traditional dominant hemisphere skills including rote verbal memory and focal language abilities, in a patient with a history of mixed language dominance, following right hemisphere ATL surgery. This case further highlights the importance of pre-surgical neuropsychological evaluation and fMRI in patients undergoing right ATL surgery.

Regional Connectivity Changes According to Seizure Outcome of Temporal Epilepsy Surgery: A Magnetoencephalography Study

For patients with medically intractable temporal lobe epilepsy (TLE), anterior temporal resection has been mostly frequent treatment...

Are low-grade gliomas of mesial temporal area alone?

Background:Temporal neocortex which appears normal on magnetic resonance imaging (MRI) may have pathological tissues in low-grade gliomas (LGG) of pure mesial temporal area. Resection of the cortex may be required together with mesial temporal glioma for satisfactory seizure and oncological outcome. The aim of this study was to explore the presence of any pathological tissue on the temporal cortex that appeared normal on preoperative MRI in patients with pure mesial temporal LGGs.Methods:This prospective study included 10 patients who underwent surgical resection of temporal lobe for LGG of mesial temporal area. The temporal neocortex with normal appearance on MRI and mesial temporal area were resected separately, and histopathological diagnosis was performed.Results:LGGs of the mesial temporal area were diagnosed with glioneuronal tumors in 7 (70%) and low-grade astrocytoma in 2 (20%) patients. Regarding the temporal cortex, gliosis and focal cortical dysplasia were found in 7 (70%) and 2 (20%) patients. In one patient temporal cortex did not contain any pathological tissue. All were seizure-free and no tumor recurrence was noted at the last follow-up.Conclusion:Mesial temporal LGGs are not alone and a high proportion of temporal neocortex appeared normal on preoperative MRI, may contain dual pathology. Thus, anterior temporal resection should be performed to have satisfactory seizure and oncological outcomes.

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

Gyratory seizures as a presentation of temporal encephalocele.

Gyratory seizures (GS) are rare and have been reported in focal (frontal and temporal) as well as generalized epilepsies. The exact neuroanatomical substrate of gyration during a seizure is not clearly understood, but is thought to be due to the involvement of the basal ganglia. The direction of gyration occurring without head version is thought to have ipsilateral cerebral origins, while gyrational seizures preceded by forced head version are suggestive of seizure onset contralateral to the direction of gyration or the presence or absence of forced head version is thought to have important implications for lateralization of seizure origins from the direction of gyration. This case describes gyratory seizures in a young boy with a temporal encephalocele. Report of MRI brain initially indicated no abnormalities, but careful review revealed a left temporal encephalocele. PET scan showed left temporal hypometabolism. The patient underwent a left anterior temporal resection with amygdalohippocampectomy (ATL + AH) and is seizure‐free for 18 months. Temporal encephalocele is the most commonly iatrogenic but may also be spontaneous, post‐traumatic, or in relation to chronic otitis media. This case suggests that gyratory seizures may be a unique presentation of temporal encephalocele and this possibility warrants investigation in patients with medically refractory epilepsy.

Determinants of IQ outcome after focal epilepsy surgery in childhood: A longitudinal case-control neuroimaging study.

Intelligence quotient (IQ) outcomes after pediatric epilepsy surgery show significant individual variation. Clinical factors such as seizure cessation or antiepileptic medication discontinuation have been implicated, but do not fully account for the heterogeneity seen. Less is known about the impact of neurobiological factors, such as brain development and resection location. This study examines clinical and neuroimaging factors associated with cognitive outcome after epilepsy surgery in childhood. Fifty-two children (28 boys, 24 girls) were evaluated for epilepsy surgery and reassessed on average 7.7years later. In the intervening time, 13 were treated pharmacologically and 39 underwent focal surgery (17 temporal, 16 extratemporal, six multilobar; mean age at surgery = 14.0years). Pre- and postsurgical assessments included IQ tests and T1-weighted brain images. Predictors of IQ change were investigated, including voxel-based analyses of resection location, and gray and white matter volume change. Overall modest IQ improvement was seen in children treated surgically, but not in those treated pharmacologically only. Applying a ≥10-point change threshold, 39% of the surgically treated children improved, whereas 10% declined. Clinical factors associated with IQ increases were lower preoperative IQ and longer follow-up duration, whereas seizure and antiepileptic medication cessation were not predictive. Among neuroimaging factors, we observed that left anterior temporal resections impacted negatively on verbal reasoning, linked to full-scale IQ decline. In contrast, gray matter volume change in ipsi- and contralesional hemispheres was positively correlated with IQ change. Voxel-based morphometry identified the gray matter volume change in the contralesional dorsolateral frontal cortex as most strongly associated with IQ improvement. We show that a variety of factors are likely to contribute to patterns of postsurgical change in IQ. Neuroimaging results indicate that left anterior temporal resections constrain development of verbal cognition, whereas simultaneously cortical growth after surgical treatment can support improvements in IQ.

Effect of Temporal Neocortical Pathology on Seizure Freeness in Adult Patients with Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. Focal cortical dysplasia is the most common dual pathology found in association with the hippocampal sclerosis. In this study, the effect of dual pathology on freedom from seizure was sought in patients with TLE. This study performed a retrospective analysis of patients with TLE who underwent surgery between 2010 and 2017. Histopathologic analysis was performed on patients with and without dual pathology in the temporal neocortex. Seizure outcomes were compared. A total of 54 patients with TLE were included. The rate of overall favorable seizure outcome was found to be 96.3%. In 53.7%, dual pathology was present in the temporal cortices in addition to the hippocampal sclerosis. Patients without dual pathology showed significantly greater freedom from seizure (P= 0.02). Patients without dual pathology had a significantly higher seizure-free rate after anterior temporal resection than patients with dual pathology. Resection of the temporal cortex in addition to mesial temporal structures seems to be reasonable for better seizure outcome.

F122. Non-lesional eating epilepsy with mesial temporal and inferior insular onset: A stereo-EEG study

Introduction Reflex epilepsy is characterized by seizures that are triggered by internal or external stimuli. Based on the complexity of the trigger, the reflex epilepsies can be subdivided into simple and complex. Eating Epilepsy (EE) is a subtype of the complex reflex epilepsies and represents a heterogeneous electro-clinical syndrome. The body of literature on EE consists mostly of a few case series with variable medical and surgical outcomes. We present a case of non-lesional EE with excellent outcome from resective epilepsy surgery after an extensive pre-surgical investigation to identify of the seizure onset zone (SOZ). Methods We retrospectively evaluated a case of drug-resistant eating-induced seizures referred for pre surgical assessment at London Health Sciences Centre Epilepsy Program, London, Canada. Patient’s data was reviewed including clinical history, neurological exam, imaging (Brain MRI and FDG-PET), neuropsychology assessment, scalp video-EEG, Stereoelectroencephalography (SEEG) and the surgical management. Results A 34-year-old gentleman has a 4-year history of seizures characterized by diffuse tingling sensation followed by loss of awareness with staring and right hand automatisms that lasted 1–2 min. 90% of his seizures were observed to be induced by eating at the beginning of a meal. His neuropsychological testing was essentially normal. Scalp video-EEG showed independent bilateral temporal spikes (R > L). Five eating-induced seizures were recorded immediately after initiation of eating with 2–3 Hz rhythmic activity over the right temporal region with perisylvian spreading. Brain MRI and PET studies were normal. Based on the electro-clinical data, the working hypothesis was right perisylvian onset of the seizures. The patient underwent intracranial recordings with stereo-EEG sampling the right temporal pole, amygdala, hippocampus, parietal operculum, temporal operculum and insula. Five seizures were captured induced by eating with stereotypical electrographic onset involving the right amygdala and hippocampus and inferior insula. Extra operative cortical stimulation (1–3.5 mA) elicited many prolonged after discharges in the same regions but they did not provoke clinical seizures. The patient thus underwent a right anterior temporal lobectomy and partial inferior insulectomy with decortication of the posterior short insular gyrus & the anterior and posterior gyri. Pathology revealed transcortical and hippocampal gliosis. He remained seizure-free (Engel 1) at his 8 months post-surgical follow-up. Conclusion This case of a drug-resistant non-lesional EE illustrates the value of stereo-EEG in the presurgical work-up that led to seizure-freedom following combined right anterior temporal lobectomy and right inferior insula resection. In non-lesional cases of drug-resistant EE, the epileptogenic zone is likely wide and it requires stereo-EEG to determine the SOZ.

Technical Modification of Amygdalo-Hippocampectomy in Temporal Lobe Epilepsy Surgery to Further Reduce Severe Neurological Complications: A Clinical-Anatomical Study.

Temporal lobe resection (TLR) including amygdalohippocampectomy (AHE) is the most frequent performed procedure in epilepsy surgery. Owing to the close anatomic relationship of the mesial temporal structures and the midbrain and choroidal fissure, the incidence of severe complications, such as postoperative stroke, is as high as 2.5%. We developed a modification of the classical technique for AHE that involves entering the choroidal fissure early via the anterior part of the frontomesial temporal horn cleft to identify the crus cerebri, posterior cerebri artery, and oculomotor nerve. In a second step, after visualization of the cleavage plane between the midbrain and middle cerebral artery, the uncus and amygdala are removed. A total of 81 patients (47 females and 34 males; mean age at surgery, 40 years) underwent TLR including AHE with our surgical modification to treat heterogeneous pathologies. The cohort included 45 patients with hippocampal sclerosis, 11 with ganglioglioma, 2 with dysembryoplastic neuroepithelioma, 2 with diffuse glioma, and 21 with other pathologies, including cavernoma, scar tissue, and mild cortical dysplasia, among others. In all patients, anterior temporal resection was performed via AHE using our modified technique. Seizure outcome was favorable after a mean follow-up of 27 months (range, 3-56 months); 64% of the patients were completely seizure-free (Engel class 1A), and 75% had an Engel class 1 outcome. There was no mortality or permanent severe neurologic complications, and the rate of surgical complications was 3.7%. Our modified AHE technique is associated with a low rate of complications in TLR for medically refractory temporal lobe epilepsy, and helps avoid permanent severe neurologic complications.

Clinical and pathological definition of temporal medium epilepsy subtypes with hypocampic sclerosis

Background and objectiveMesial temporal lobe epilepsy with hippocampal sclerosis is the most common cause of refractory epilepsy, and the most common indication for surgery. Although effective, surgery fails in up to 40% of patients. The objective of our study was to establish a correlation between the different histological subtypes of mesial temporal lobe epilepsy with hippocampal sclerosis and the prognosis, seizures control, side effects and anticonvulsivant drug withdrawal in patients with refractory epilepsy. Patients and methodClinical histories and anatomopathological specimens of 228 patients with temporal epilepsy surgically obtained at our hospital between 1993 and 2014 were retrospectively analyzed. All patients underwent a standard preoperative evaluation and anterior temporal resection (modified from Spencer). The anatomopathological study included the standard hematoxylin–eosin and immunohistochemical protocol, with special interest in the assessment of neuronal loss with NeuN. Seizure control was assessed according to the scale of results of the ILAE and Engel. The mean follow-up was 8.6 years (2–19). ResultsAt 10 years after the intervention, 67.9% of patients were seizure-free (ILAE 1) and as many as 77.5% of the patients were seizure-free (Engel 1) at the end of the follow-up. The probability of not having a seizure (ILAE 1) after surgery at 2 (p=0.042), 5 (p=0.001) and 7 years (p=0.22) was higher in classic and severe forms compared to isolated sclerosis CA1 and CA4 forms. Higher neuronal loss measured with the NeuN immunostain in CA1 was associated with better outcome in seizure management (multivariate analysis, p=0.08). The presence of a personal history of epilepsy was associated with greater neuronal loss in CA1 (p=0.028) and CA3 (p=0.034), and the presence of psychic auras was related with greater neuronal loss in CA3 (p=0.025). In our case, the probability of medication withdrawal was related to the presence of personal history (p=0.003) and, inversely, to neuronal loss in CA1 (p=0.036) and CA3 (p=0.038). The greatest impairment of verbal memory occurred in those patients with a lower neuronal loss in CA1 (p=0.023), CA2 (p=0.049) and CA3 (p=0.035). ConclusionsThe results indicate that the classical and severe subtypes have a better prognosis in the control of seizures against the atypical forms, validating the clinical and prognostic utility of the classification of histological subtypes of hippocampal sclerosis from the ILAE. The value of the immunohistochemistry in the mesial temporal lobe epilepsy with hippocampal sclerosis has been demonstrated as a key element to determine the neuropsychological prognosis and seizure management of the patients after surgery.

Surgical Treatment of Mesiotemporal Lobe Epilepsy: Which Approach is Favorable?

Mesiotemporal lobe epilepsy is one of the most frequent causes for pharmacoresistant epilepsy. Different surgical approaches to the mesiotemporal area are used. To analyze epileptological and neuropsychological results as well as complications of different surgical strategies. This retrospective study is based on a consecutive series of 458 patients all harboring pharmacoresistant mesiotemporal lobe epilepsy. Following procedures were performed: standard anterior temporal lobectomy, anterior temporal or key-hole resection, extended lesionectomy, and transsylvian and subtemporal selective amygdalohippocampectomy. Postoperative outcome was evaluated according to different surgical procedures. Overall, 1 yr after surgery 315 of 432 patients (72.9%) were classified Engel I; in particular, 72.8% were seizure-free after anterior temporal lobectomy, 76.9% after key-hole resection, 84.4% after extended lesionectomy, 70.3% after transylvian selective amygdalohippocampectomy, and 59.1% after subtemporal selective amygdalohippocampectomy. No significant differences in seizure outcome were found between different resective procedures, neither in short-term nor long-term follow-up. There was no perioperative mortality. Permanent morbidity was encountered in 4.4%. There were no significant differences in complications between different resection types. In the majority of patients, selective attention improved following surgery. Patients after left-sided operations performed significantly worse regarding verbal memory as compared to right-sided procedures. However, surgical approach had no significant effect on memory outcome. Different surgical approaches for mesiotemporal epilepsy analyzed resulted in similar epileptological, neuropsychological results, and complication rates. Therefore, the approach for the individual patient does not only depend on the specific localization of the epileptogenic area, but also on the experience of the surgeon.

Visual field defects following different resective procedures for mesiotemporal lobe epilepsy

IntroductionOne of the most common side effects of mesiotemporal lobe resection in patients with medically intractable epilepsy are visual field defects (VFD). While peripheral defects usually remain unnoticed by patients, extended VFD influence daily life activities and can, in particular, affect driving regulations. This study had been designed to evaluate frequency and extent of VFD following different surgical approaches to the mesiotemporal area with respect to the ability to drive. Materials and methodsThis study comprises a consecutive series of 366 patients operated at the Epilepsy Center in Freiburg for intractable mesiotemporal lobe epilepsy from 1998 to 2016. The following procedures were performed: standard anterior temporal lobectomy (ATL: n=134; 37%), anterior temporal or keyhole resection (KH: n=53; 15%), and selective amygdalohippocampectomy via the transsylvian (tsAHE: n=145; 40%) and the subtemporal (ssAHE: n=34; 9%) approach. Frequency and extent of postoperative VFD were evaluated in relation to different surgical procedures. According to the German driving guidelines, postoperative VFD were classified as driving-relevant VFD with the involvement of absolute, homonymous central scotoma within 20° and driving-irrelevant VFD with either none or exclusively minor VFD sparing the center. ResultsPostoperative visual field examinations were available in 276 of 366 cases. Postoperative VFD were observed in 202 of 276 patients (73%) and were found to be driving-relevant in 133 of 276 patients (48%), whereas 69 patients (25%) showed VFD irrelevant for driving. Visual field defects were significantly less likely following ssAHE compared with other temporal resections, and if present, they were less frequently driving-relevant (p<0.05), irrespective of the side of surgery. ConclusionSubtemporal sAHE (ssAHE) caused significantly less frequently and less severely driving-relevant VFD compared with all other approaches to the temporal lobe, irrespective of the side of surgery.

Mapping the language landscape: A systematic review of interventions used in awake craniotomy

Mapping the language landscape: A systematic review of interventions used in awake craniotomy

Beta modulation reflects name retrieval in the human anterior temporal lobe: an intracranial recording study.

Naming people, places, and things is a fundamental human ability that is often impaired in patients with language-dominant anterior temporal lobe (ATL) dysfunction or ATL resection as part of epilepsy treatment. Convergent lines of evidence point to the importance of the ATL in name retrieval. The physiologic mechanisms that mediate name retrieval in the ATL, however, are not well understood. The purpose of this study was to characterize the electrophysiologic responses of the human ATL during overt cued naming of famous people and objects. Eight neurosurgical patients with suspected temporal lobe epilepsy who underwent implantation of intracranial electrodes for seizure focus localization were the subjects of this study. Specialized coverage of the ATL was achieved in each subject. The subjects named pictures of U.S. presidents and images of common hand-held tools. Event-related band power was measured for each ATL recording site. Both the left and right ATL demonstrated robust and focal increases in beta-band (14-30 Hz) power during person and tool naming. The onset of this response typically occurred at 400 ms but sometimes as early as 200 ms. Visual naming of famous people and tools is associated with robust and localized modulation of the beta band in both the left and right ATL. Measurement of visual naming responses may provide the groundwork for future mapping modalities to localize eloquent cortex in the ATL.

When is temporal lobe epilepsy not temporal lobe epilepsy?

This scientific commentary refers to ‘Temporal plus epilepsy is a major determinant of temporal lobe surgery failures’, by Barba et al. . (doi:10.1093/brain/awv372). Stereotactic electroencephalography (SEEG) originated in France in the 1950s. Bancaud and Talairach, at St. Anne’s Hospital in Paris, introduced this approach to define the 3D extent of dysfunctional brain tissue surrounding intraparenchymal brain tumours, and more specifically, to define epileptogenic brain tissue in patients with pharmacoresistant epileptic seizures (Bancaud et al. , 1975). The approach required a hypothesis that would enable the placement of multiple, mostly unilateral, depth electrodes to sample a reasonably limited number of regions of interest. The results then guided a tailored surgical resection. This technique was adapted by Crandall et al. (1963) at UCLA for patients with suspected mesial temporal lobe epilepsy. Crandall, however, used a standardized, bilaterally symmetrical, depth electrode approach, designed to sample those structures known to be primarily involved in generating limbic seizures. Because French law did not allow Bancaud and Talairach to leave their electrodes in place for more than a few hours, their analyses were based on interictal activity, as well as electrically and chemically induced seizures. Crandall, therefore, was the first to perform chronic depth electrode recording, over days and weeks, in order to capture spontaneous ictal events. Because investigators at UCLA had recently developed an EEG telemetry device for NASA to record from chimpanzees orbiting in space, Crandall was also able to use this new technology to establish EEG telemetry for long-term monitoring of epileptic seizures. Data were used to determine that the epileptogenic region was contained within the area of a standardized anterior temporal resection (Falconer, 1953), which was then performed routinely. Two schools of invasive presurgical evaluation for epilepsy surgery then evolved: the French school, which performed classical SEEG, using multiple electrodes …

Epilepsy with temporal encephalocele: Characteristics of electrocorticography and surgical outcome

Temporal lobe encephaloceles (TEs) are increasingly identified in patients with epilepsy due to advances in neuroimaging. Select patients become seizure-free with lesionectomy. In practice, however, many of these patients will undergo standard anterior temporal lobectomy. Herein we report on the first series of patients with refractory temporal lobe epilepsy (TLE) with encephalocele to undergo chronic or intraoperative electrocorticography (ECoG) in order to characterize the putative epileptogenic nature of these lesions and help guide surgical planning. This retrospective study includes nine adult patients with magnetic resonance imaging/computed tomography (MRI/CT)-defined temporal encephalocele treated between 2007 and 2014 at University of California San Francisco (UCSF). Clinical features, ECoG, imaging, and surgical outcomes are reviewed. Six patients underwent resective epilepsy surgery. Each case demonstrated abnormal epileptiform discharges around the cortical area of the encephalocele. Two underwent tailored lesionectomy and four underwent lesionectomy plus anterior medial temporal resection. Postoperatively, five patients, including both with lesionectomy only, had Engel class Ia surgical outcome, and one had a class IIb surgical outcome. The role of TE in the pathogenesis of epilepsy is uncertain. ECoG can confirm the presence of interictal epileptiform discharges and seizures arising from these lesions. Patients overall had a very good surgical prognosis, even with selective surgical approaches.

The course and the anatomo‐functional relationships of the optic radiation: a combined study with ‘post mortem’ dissections and ‘in vivo’ direct electrical mapping

Even if different dissection, tractographic and connectivity studies provided pure anatomical evidences about the optic radiations (ORs), descriptions of both the anatomical structure and the anatomo-functional relationships of the ORs with the adjacent bundles were not reported. We propose a detailed anatomical and functional study with 'post mortem' dissections and 'in vivo' direct electrical stimulation (DES) of the OR, demonstrating also the relationships with the adjacent eloquent bundles in a neurosurgical 'connectomic' perspective. Six human hemispheres (three left, three right) were dissected after a modified Klingler's preparation. The anatomy of the white matter was analysed according to systematic and topographical surgical perspectives. The anatomical results were correlated to the functional responses collected during three resections of tumours guided by cortico-subcortical DES during awake procedures. We identified two groups of fibres forming the OR. The superior component runs along the lateral wall of the occipital horn, the trigone and the supero-medial wall of the temporal horn. The inferior component covers inferiorly the occipital horn and the trigone, the lateral wall of the temporal horn and arches antero-medially to form the Meyer's Loop. The inferior fronto-occipital fascicle (IFOF) covers completely the superior OR along its entire course, as confirmed by the subcortical DES. The inferior longitudinal fascicle runs in a postero-anterior and inferior direction, covering the superior OR posteriorly and the inferior OR anteriorly. The IFOF identification allows the preservation of the superior OR in the anterior temporal resection, avoiding post-operative complete hemianopia. The identification of the superior OR during the posterior temporal, inferior parietal and occipital resections leads to the preservation of the IFOF and of the eloquent functions it subserves. The accurate knowledge of the OR course and the relationships with the adjacent bundles is crucial to optimize quality of resection and functional outcome.