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In the typically developing (TD) brain, neural representations for visual stimulus categories (e.g., faces, objects, and words) emerge in bilateral occipitotemporal cortex (OTC), albeit with weighted asymmetry; in parallel, recognition behavior continues to be refined. A fundamental question is whether two hemispheres are necessary or redundant for the emergence of neural representations and recognition behavior typically distributed across both hemispheres. The rare population of patients undergoing unilateral OTC resection in childhood offers a unique opportunity to evaluate whether neural computations for visual stimulus individuation suffice for recognition with only a single developing OTC. Here, using functional magnetic resonance imaging, we mapped category selectivity (CS) and neural representations for individual stimulus exemplars using repetition suppression (RS) in the non-resected hemisphere of pediatric OTC resection patients ( n = 9) and control patients with resection outside of OTC ( n = 12), as well as in both hemispheres of TD controls ( n = 21). There were no univariate group differences in the magnitude of CS or RS or any multivariate differences (per representational similarity analysis) in neural activation to faces, objects, or words across groups. Notwithstanding their comparable neural profiles, accuracy of OTC resection patients on face and object recognition, but not word recognition, was statistically inferior to that of controls. The comparable neural signature of the OTC resection patients' preserved hemisphere and the other two groups highlights the resilience of the system following damage to the contralateral homologue. Critically, however, a single OTC does not suffice for normal behavior, and, thereby, implicates the necessity for two hemispheres., Competing Interests: Declaration of Interests MB is a founder of a company, Precision Neuroscopics.

Background Major depressive disorder (MDD) is a system-level disorder affecting multiple functionally integrated cerebral networks. Nevertheless, their temporospatial organization and potential disturbance remain mostly unknown. The present report tested the hypothesis that deficient temporospatial network organization separates MDD and healthy controls (HC), and is linked to symptom severity of the disorder. Methods Eyes-closed resting-state magnetoencephalographic (MEG) recordings were obtained from twenty-two MDD and twenty-two HC subjects. Beamforming source localization and functional connectivity analysis were applied to identify frequency-specific network interactions. Then, a novel virtual cortical resection approach was used to pinpoint putatively critical network controllers, accounting for aberrant cerebral connectivity patterns in MDD. Results We found significantly elevated frontolimbic and frontocentral connectivity mediated by gamma (30–48 Hz) activity in MDD versus HC, and the right amygdala was the key differential network controller accounting for aberrant cerebral connectivity patterns in MDD. Furthermore, this frontolimbic and frontocentral gamma-band hyper-connectivity was positively correlated with depression severity. Limitations The overall sample size was small, and we found significant effects in the deep limbic regions with resting-state MEG, the reliability of which was difficult to corroborate further. Conclusions Overall, these findings support a notion that the right amygdala critically controls the exaggerated gamma-band frontolimbic and frontocentral connectivity in MDD during the resting-state condition, which potentially constitutes pre-established aberrant pathways during task processing and contributes to MDD pathology.

Electrocorticography (ECoG) data can be used to estimate brain-wide connectivity patterns. Yet, the invasiveness of ECoG, incomplete cortical coverage, and variability in electrode placement across individuals make the network analysis of ECoG data challenging. Here, we show that the architecture of whole-brain ECoG networks and the factors that shape it can be studied by analysing whole-brain, interregional and band-limited ECoG networks from a large cohort-in this case, of individuals with medication-resistant epilepsy. Using tools from network science, we characterized the basic organization of ECoG networks, including frequency-specific architecture, segregated modules and the dependence of connection weights on interregional Euclidean distance. We then used linear models to explain variabilities in the connection strengths between pairs of brain regions, and to highlight the joint role, in shaping the brain-wide organization of ECoG networks, of communication along white matter pathways, interregional Euclidean distance and correlated gene expression. Moreover, we extended these models to predict out-of-sample, single-subject data. Our predictive models may have future clinical utility; for example, by anticipating the effect of cortical resection on interregional communication.

The human cortical visual system consists of two major pathways, a ventral pathway that subserves perception and a dorsal pathway that subserves visuomotor control. These pathways follow dissociable developmental trajectories, and, accordingly, might be differentially susceptible to neurodevelopmental disorders or injuries. Previous studies have found that children with cortical resections of the ventral visual pathway retain largely normal visuoperceptual abilities. Whether visually guided actions, supported by computations carried out by the dorsal pathway, follow a similar pattern remains unknown. To address this question, we examined visuoperceptual and visuomotor behaviors in a pediatric patient, TC, who underwent a cortical resection that included portions of the left ventral and dorsal pathways. We collected data when TC used her right and left hands to perceptually estimate the width blocks that varied in width and length, and, separately, to grasp the same blocks. TC’s perceptual estimation performance was comparable to that of controls, independent of the hand used. In contrast, relative to controls, she showed reduced visuomotor sensitivity to object shape and this was more evident when she grasped the objects with her contralesional right hand. These results provide evidence for a striking difference in the reorganization profiles of the two visual pathways. This difference supports the notion that the two pathways exhibit differential susceptibility to neurodevelopmental disorders.

Purpose: Hybrid PET/MR is a promising tool in focal drug-resistant epilepsy, however the additional value for the detection of epileptogenic lesions and surgical decision-making remains to be established.Methods: We retrospectively compared 18F-FDG PET/MR images with those obtained by a previous 18F-FDG PET co-registered with MRI (PET+MR) in 25 consecutive patients (16 females, 13-60 year-old) investigated for focal drug-resistant epilepsy. Visual analysis was performed by two readers blinded from imaging modalities, asked to assess the technical characteristics (co-registration, quality of images), confidence in results, location of PET abnormalities and presence of a structural lesion on MRI. The clinical impact on surgical strategy and outcome was assessed independently.Results: The location of epilepsy was temporal in 9 patients and extra-temporal in 16 others. MRI was initially considered negative in 21 of them. PET alone demonstrated metabolic abnormalities in 19 cases (76%), and the co-registration with MRI allowed the detection of 4 additional structural lesions. PET/MR was considered better performing than PET+MR in 56% of patients. The increase in sensitivity was 13% and new structural lesions (mainly focal cortical dysplasias) were detected in 6 patients (24%). Change of surgical decision-making was substantial for 40% of patients, consisting in avoiding invasive monitoring in 6 patients and modifying the planning in 4 others. Seizure-free outcome was obtained in 13/14 patients who underwent a cortical resection.Conclusion: Hybrid PET/MR improves the detection of epileptogenic lesions, allowing to optimize the presurgical work-up and to increase the proportion of successful surgery even in the more complex cases.

Despite the relative successes in the surgical treatment of pharmacoresistant epilepsy, there is rather little research on the neural (re)organization that potentially subserves behavioral compensation. Here, we examined the post-surgical functional connectivity (FC) in children and adolescents who have undergone unilateral cortical resection and, yet, display remarkably normal behavior. Conventionally, FC has been investigated in terms of the mean correlation of the BOLD time courses extracted from different brain regions. Here, we demonstrated the value of segregating the voxel-wise relationships into mutually exclusive populations that were either positively or negatively correlated. While, relative to controls, the positive correlations were largely normal, negative correlations among networks were increased. Together, our results point to reorganization in the contralesional hemisphere, possibly suggesting competition for cortical territory due to the demand for representation of function. Conceivably, the ubiquitous negative correlations enable the differentiation of function in the reduced cortical volume following a unilateral resection.

Despite the relative successes in the surgical treatment of pharmacoresistant epilepsy, there is rather little research on the neural (re)organization that potentially subserves behavioral compensation. Here, we examined the post-surgical functional connectivity (FC) in children and adolescents who have undergone unilateral cortical resection and, yet, display remarkably normal behavior. Conventionally, FC has been investigated in terms of the mean correlation of the BOLD time courses extracted from different brain regions. Here, we demonstrated the value of segregating the voxel-wise relationships into mutually exclusive populations that were either positively or negatively correlated. While, relative to controls, the positive correlations were largely normal, negative correlations among networks were increased. Together, our results point to reorganization in the contralesional hemisphere, possibly suggesting competition for cortical territory due to the demand for representation of function. Conceivably, the ubiquitous negative correlations enable the differentiation of function in the reduced cortical volume following a unilateral resection.

OBJECTIVEAlthough epilepsy surgery is an effective treatment option, at least 20%–40% of patients can continue to experience uncontrolled seizures resulting from incomplete resection of the lesion, epileptogenic zone, or secondary epileptogenesis. Reoperation could eliminate or improve seizures. Authors of this study evaluated outcomes following reoperation in a pediatric population.METHODSA retrospective single-center analysis of all patients who had undergone resective epilepsy surgery in the period from 2001 to 2013 was performed. After excluding children who had repeat hemispherotomy, there were 24 children who had undergone a second surgery and 2 children who had undergone a third surgery. All patients underwent MRI and video electroencephalography (VEEG) and 21 underwent magnetoencephalography (MEG) prior to reoperation.RESULTSThe mean age at the first and second surgery was 7.66 (SD 4.11) and 10.67 (SD 4.02) years, respectively. The time between operations ranged from 0.03 to 9 years. At reoperation, 8 patients underwent extended cortical resection; 8, lobectomy; 5, lesionectomy; and 3, functional hemispherotomy. One year after reoperation, 58% of the children were completely seizure free (International League Against Epilepsy [ILAE] Class 1) and 75% had a reduction in seizures (ILAE Classes 1–4). Patients with MEG clustered dipoles were more likely to be seizure free than to have persistent seizures (71% vs 40%, p = 0.08).CONCLUSIONSReoperation in children with recurrent seizures after the first epilepsy surgery could result in favorable seizure outcomes. Those with residual lesion after the first surgery should undergo complete resection of the lesion to improve seizure outcome. In addition to MRI and VEEG, MEG should be considered as part of the reevaluation prior to reoperation.

Children with unilateral resections of ventral occipito-temporal cortex (VOTC) typically do not evince visual perceptual impairments, even when relatively large swathes of VOTC are resected. In search of possible explanations for this behavioral competence, we evaluated white matter microstructure and connectivity in eight pediatric epilepsy patients following unilateral cortical resection and 15 age-matched controls. To uncover both local and broader resection-induced effects, we analyzed tractography data using two complementary approaches. First, the microstructural properties were measured in the inferior longitudinal and the inferior fronto-occipital fasciculi, the major VOTC association tracts. Group differences were only evident in the ipsilesional, and not in the contralesional, hemisphere, and single-subject analyses revealed that these differences were limited to the site of the resection. Second, graph theory was used to characterize the connectivity of the contralesional occipito-temporal regions. There were no changes to the network properties in patients with left VOTC resections nor in patients with resections outside the VOTC, but altered network efficiency was observed in two cases with right VOTC resections. These results suggest that, in many, although perhaps not all, cases of unilateral VOTC resections in childhood, the white matter integrity in the preserved contralesional hemisphere along with residual neural activity might be sufficient for normal visual perception.HighlightsThere is well-circumscribed white matter damage in pediatric epilepsy after surgeryWhite matter pathways are normal distal as well as contralesional to the resectionContralesional network properties differ after left or right hemisphere resectionPreserved cortex and white matter may be sufficient for normal perception

Worldwide experts consider presurgical electrocorticography (ECoG) or intracerebral electrode monitoring a necessary evaluation tool for a selected population of patients with focal epilepsy. The goal of chronic ECoG monitoring at bedside generally includes localizing the seizure onset zone presumably responsible for generation of habitual seizures and localizing the eloquent areas to be preserved for avoiding major functional deficits following cortical resection. Language function directly determines the quality of life in patients following epilepsy surgery; thus, each surgical team makes the best effort to localize the language areas before performing resective surgery.

There is no consensus regarding the ideal treatment for odontogenic myxomas, an odontogenic mesenchymal neoplasm. Various authors have suggested en bloc resection due to a concern regarding inadequate clearance while others have suggested more conservative treatment. We present a case managed by buccal cortical resection and an iliac crest bone graft. The patient had no recurrence for over 7 years.

Twenty-four patients with intractable partial epilepsy underwent surgery between 1969 and 1988. Localization was by non-invasive means using scalp EEG and CT. In 12 cases the focus was temporal and in eight frontal. Craniotomy was undertaken with intraoperative electrocorticography (ECoG). Ten cases had a standard temporal lobectomy, seven a topectomy, four topectomy with tumour excision and one tumour excision alone. Two cases did not have a resection. Pathology revealed a mass lesion in 12 cases, hippocampal sclerosis in two and gliosis in six. Mean length of follow-up was 7.4 years. Fourteen patients (64%) were seizure free, two (9%) almost seizure free, four (18%) had worthwhile improvement and two (9%) no improvement. Of the temporal resections, 9 out of 12 (75%) were seizure free and of the extratemporal resections 5 out of 10 (50%) were seizure free. Removal of a mass lesion carried the most favourable prognosis for seizure outcome: 10 out of 12 (83%) of the cases with mass lesions, but 3 out of 6 (50%) of the cases with gliosis were seizure free. In two of the frontal resections removal of tumour resulted in disappearance of contralateral frontal independent spikes. It is concluded that where sufficient information exists to localize seizure activity by non-invasive means, invasive recording is unnecessary. The utility of intraoperative ECoG is discussed. It may be of limited use in cases of standard resection or when a mass lesion is present, but ECoG can prove useful to delineate the epileptogenic area in cases where there is no mass lesion and the results can still be rewarding.

For 20 million people with drug-resistant epilepsy, recurring, spontaneous seizures have a devastating impact on daily life. The ecacy of surgical treatment for controlling seizures is hindered by a poor understanding of how some seizures spread to and synchronize surrounding tissue while others remain focal. To pinpoint network regions that regulate seizure evolution, we present a novel method to assess changes in synchronizability in response to virtually lesioning cortical areas in a validated computational network model. In human patients implanted with electrocorticographic sensors, we apply our virtual cortical resection technique to time-varying functional networks and identify control regions that synchronize or desynchronize cortical areas using an antagonistic push-pull control scheme to raise or lower synchronizability. Our results suggest that synchronizability before seizures predicts seizure evolution: in focal seizures, the strongest controllers are located outside seizure-generating areas. These methods,while applied here to epilepsy, are generalizable to other brain networks, and have wide applicability in isolating and mapping functional drivers of brain dynamics in health and disease. dynamic network neuroscience | epileptic network | synchronizability | push-pull control | diffusion | seizure evolution

Medically intractable epilepsy is a clinical condition of concern that arises when a patient with epilepsy suffers seizures, despite a trial of two or more antiepileptic drugs (AEDs) suitable for the type of epilepsy that are prescribed at maximum tolerated doses, does not achieve control of seizures. This diagnosis could be related to cortical dysplasias. We report the case of a 5-year-old girl with a previous normal neurological development and no family history of epilepsy who presented with focal-type seizures at age 4. She started treatment by taking different AEDs for seizure control. She continued having frequent seizures that sometimes progressed to generalized seizures and status epilepticus. After a focal cortical resection performed in the area where interictal spikes were detected, the pathology confirmed a type IIb cortical dysplasia as the cause of the epilepsy. This article discusses cortical dysplasias as a cause of pharmacoresistant epilepsy and its treatment. © 2015 The Authors.

Epilepsy is a chronic disorder characterized by recurrent and unprovoked seizures. The lifetime risk of developing epilepsy is 4%. Approximately 90% of the incident cases in adults have partial epilepsy. The initial response to medication is of prognostic importance. Patients with symptomatic neurologic disease, foreign-tissue lesion, or developmental delay are less likely to be rendered seizure free. The goal of treatment is to render the individual seizure free. Many patients with partial epilepsy will not attain a seizure remission with antiepileptic drug therapy. Epilepsy surgery is an effective and safe alternative form of therapy for selected patients with intractable partial epilepsy. Electronic stimulation is being considered for patients with partial seizures who are not candidates for a focal cortical resection.

Mirror movements may be congenital or acquired. There are few reports of acquired mirror movements in pediatric patients. Further, mirror movements in children with epilepsy have rarely been reported. A 9-year old male, with intractable partial epilepsy resulting from polymicrogyria of the right hemisphere, underwent cortical resection of the right frontotemporoparietal region for a malformation of cortical development. He developed left hemiplegia and mirror movements in the left hand in the postoperative period. Four months after surgery, he remained seizure-free with mild residual left-sided hemiplegia and persistent mirror movements. Mechanisms postulated for mirror movements include aberrant pyramidal tract development and transcallosal inhibitory pathways. The latter mechanism might have contributed to the mirror movements observed in this child. This study is the first report of mirror movements following focal cortical resection for intractable epilepsy due to polymicrogyria.

Resume Nous ne retrouvons pas, chez l’enfant, la grande proportion de chirurgies temporales que l’on note chez l’adulte. Les indications de resection corticale, temporale ou frontale, peuvent etre resumees de la facon suivante : il faut que l’epilepsie provienne d’une region precise et localisee du cerveau, que la pharmaco-resistance soit averee, que le foyer soit extirpable chirurgicalement, et que le handicap soit suffisamment severe. L’hemispherotomie est une technique curative indiquee en cas de pathologie hemispherique, qui peut etre developpementale, acquise, ou encore progressive. La chirurgie palliative est essentiellement representee par la callosotomie, dont la principale indication est celle de crises avec chutes atoniques. La transsection sous-piale multiple, indiquee en cas de localisation du foyer epileptogene en zone eloquente, est relativement peu pratiquee. Les principaux risques lies aux resections corticales sont representes par le deficit moteur controlateral, lie a une lesion per-operatoire du reseau sylvien, ou de l’artere choroidienne anterieure, ou encore des aires motrices elles-memes. Le risque de deterioration neuropsychologique post-operatoire est faible. Le risque de syndrome de dysconnexion apres callosotomie est egalement faible. En conclusion, il se degage de cette revue de la litterature, un fort consensus pour rechercher, des que la pharmaco-resistance est averee, une solution chirurgicale a l’epilepsie de l’enfant.

Contains fulltext : 143482.pdf (Publisher’s version ) (Open Access) Research Question Recent discoveries have challenged the traditional view that the thalamus is the primary source driving spike-and-wave discharges (SWDs). At odds, SWDs in genetic absence models have a cortical focal origin in the deep layers of the perioral region of the somatosensory cortex. The present study examines the effect of unilateral and bilateral surgical resection of the assumed focal cortical region on the occurrence of SWDs in anesthetized WAG/Rij rats, a well described and validated genetic absence model. Methods Male WAG/Rij rats were used: 9 in the resected and 6 in the control group. EEG recordings were made before and after craniectomy, after unilateral and after bilateral removal of the focal region. Results SWDs decreased after unilateral cortical resection, while SWDs were no longer noticed after bilateral resection. This was also the case when the resected areas were restricted to layers I-IV with layers V and VI intact. Conclusions These results suggest that SWDs are completely abolished after bilateral removal of the focal region, most likely by interference with an intracortical columnar circuit. The evidence suggests that absence epilepsy is a network type of epilepsy since interference with only the local cortical network abolishes all seizures. 10 p.

The presentation and treatment of a patient with extra-temporal non-lesional partial epilepsy is discussed herein. His clinical semiology was consistent with supplementary motor area seizures; however, MR imaging did not demonstrate a lesion. A region of stable cortical glucose hypermetabolism in the left frontal region was noted with 2-fluoro-2-deoxy-D-glucose (FDG)-PET. This was consistent with the frequent interictal discharges evident over the left fronto-temporal region and the stereotypic high amplitude ictal discharges arising with highest amplitude from the left frontal region. Epileptiform activity evident on an intracranial 64-point subdural recording grid placed over the left dorsolateral frontal cortex confirmed a distribution concordant with FDG-PET findings. The subsequent resection was guided by the PET and EEG findings rather than structural MR imaging, and a limited cortical resection led to an immediate and substantial reduction in seizure frequency.

7 cases of pure multiple subpial transection (MST) without associated cortical resection, for treatment of pharmaco-resistant partial epilepsy localized in highly functional cortical area, are reported. The transections were performed following the technique described by Morrell. The follow-up period ranged from 1 to 4 years. MST induced no significant neurological handicap: only 2 patients experiencing a transitory sensory-motor deficit and with total recovery within 1 month. With respect to seizures, 5 patients were improved with a decrease in seizure frequency of 100, 95, 75, 60 and 40%, respectively. Complex partial seizures changed postoperatively into simple partial seizures in 1 case. In conclusion, this procedure seems to be adequate, although no statistically significant results are available at this time. In our series, we believe failures could be attributed to either a very restricted area of transection or to an incorrect delimitation of the epileptic focus.

Background: The observation that resection of structural lesions of the frontal lobe provides an effective treatment of intractable epilepsy has been made by surgeons specializing in this field for over sixty years! However, the excellent results achieved when such resections are coupled with the use of modern diagnostic and operative technologies are not fully appreciated by the modern clinician. Methods: We review the results of resection of large post traumatic frontal lesions in six patients with intractable frontal seizures. No invasive EEG recording was required pre-operatively. Results: The imaging characteristics of the underlying lesions, usually due to depressed skull fractures are illustrated. Surgical treatment rendered five patients seizure free and the sixth had over 85% improvement in seizure frequency. Conclusions: Modern imaging permits ready visualization of the post traumatic lesions with cause intractable seizures. It is important to recognize that resection of these post traumatic scars usually leads to excellent seizure control.

Invasive intracranial monitoring with subdural grids has led to a greater appreciation of cortical function and the discovery of ictal onset either independently or in conjunction with deep structures. With the description of multiple subpial transections the armamentarium for surgical control of intractable seizures has been expanded. Utilizing invasive intracranial monitoring with subdural grids and strips, a large series of patients with intractable complex partial seizures originating in exquisite cortex, and in some cases additionally in deep structures, have undergone surgery. These patients would previously have been judged not to be candidates for surgical control of seizures. We will present 9-month or greater follow-up in an ongoing series of patients undergoing cortical resection and subpial transections in whom there has been a statistical improvement in control or alleviation of their seizure disorder. The report will specifically discuss outcomes as related to exquisite cortex, motor, sensory and language functions, as well as clinical results and EEG.

This case study with video recording describes a brief neurological examination of a rare post-surgical finding in a patient with intractable seizures who had a right parietal topectomy in order to cure focal and disabling epilepsy. Contemporaneously during the resection and while awake intraoperatively, the patient developed features characterised by involuntary, purposeless, and almost ballistic movements of the contralateral left upper extremity. These involved the shoulder and, more distally, the arm with less involvement of the hand itself and some clonic movement at the elbow, persisting for approximately 24 hours after surgery. Although identified in only one case in our series, we have named the resulting clinical phenomenology "parietal hand syndrome". A Medline search does not reveal any other such case in the English literature with the clinical elements and actual video documentation of neurological examination noted in our case report in the immediate post-operative setting. In this regard, this is a unique clinical report. [Published with video sequences].

Despite the use of hemispherectomy in the treatment of medically refractory seizures since the early 1950's, few studies published have documented neuropathologic findings in the resected specimens. This report describes the neuropathologic findings in 38 children who underwent either hemispherectomy or multilobar cortical resection as treatment for medically intractable epilepsy between 1986 and 1990. Examination of the resected specimens revealed a variety of abnormalities which fell into four broad categories. Malformations or hamartomatous lesions were the dominant finding in 15 patients, whereas encephalomalacic lesions were the most prominent abnormality in 16; chronic pathogen-free encephalitits (Rasmussen's encephalitis) was present in 3 and an additional 3 children had Sturge-Weber-Dimitri syndrome. There were no gross or microscopic abnormalities in 1 patient. This report provides the first comprehensive description of the pathologic findings in a series of children with refractory epilepsy of varying types treated by hemispherectomy-multilobar resection.

A retrospective analysis was performed in 30 patients who underwent computer-assisted stereotactic resection of intra-axial mass lesions with intractable partial epilepsy. Mean follow-up was 4.1 years (2-5.5), mean age 21 years (3-45) and mean duration of seizures 8.4 years (1-26). Pathology consisted of vascular malformations in 11, glial neoplasms in 11, cortical dysplasia in 4 and gliosis in 3, and no diagnostic abnormality was found in 2 patients. The location of the lesions in some cases may have precluded a standard craniotomy and cortical resection, e.g. precentral gyrus (5), post-central gyrus (5) and deep-seated left posterior temporal region (4). Operative morbidity involved 3 patients who developed motor or language deficits. Four patients were lost to follow-up. Thirteen patients out of 26 (50%) were class I, 3 (12%) were class II, 4 (15%) were class III and 6 (23%) were class IV. These findings suggest that stereotactic lesion resection in selected cases (e.g. where lesions are located in eloquent brain regions) can be useful in providing a histological diagnosis of the epileptogenic foci and result in a favorable reduction in seizure activity without the need for a standard cortical resection.