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Absence of deconnexion syndrome in two patients with partial section of the neocommissure
... ; https://doi.org/10.1101/2025.02. 16.638524 doi: bioRxiv preprint 4 callosotomy may provide causal insights into the functional specificity of CC subregions by examining which types of information can still be integrated and which cannot, based on the location and extent of the resection. ...
... 15 Thus, only a few such cases exist in the literature, and their findings are mixed: some show integrated behavior across multiple modalities, suggesting that a small portion of the posterior CC fibers may support broader interhemispheric integration beyond visual information. 16 Others reported tactile but not visual disconnection, in line with a linear, topographic model of the CC, where the splenium alone is insufficient to integrate information beyond the visual domain. 17 Importantly, however, in the former case, 16 because no MRI data was available, it remains unclear whether only the splenium was spared or if additional CC structures, such as the posterior midbody, were also preserved. ...
... Patients with callosal disruptions caused by pathological lesions generally exhibit selective functional disruptions consistent with the topographic organization of the CC. 9 However, these patients' behavioral outcomes often differ from those observed in callosotomy cases. 16 This distinction likely stems from fundamental differences in how the CC disruption occurs: callosotomy involves sudden, targeted disruption of white matter, whereas pathological lesions often develop gradually and may include extra-callosal damage. After callosotomy, the system suddenly and specifically loses the callosal fibers through a very targeted surgical resection, to which it may respond differently as compared to gradual, diffuse disruption. ...
Much of the sensory-motor processing in the human brain is lateralized to either hemisphere, with the corpus callosum integrating these distinct processes into a seemingly unified conscious experience. The corpus callosum is thought to be topographically organized, with different subregions along its anterior-to-posterior axis involved in integrating information across different sensory modalities and cognitive domains. In complete callosotomy patients, where the corpus callosum is fully severed, this integration is typically disrupted across these domains. But which types of inter-hemispheric integration can still be preserved with small posterior callosal remnants? We studied four callosotomy patients-three complete and one partial with approximately 1 cm of preserved splenium-using an array of lateralized visual, tactile, visuospatial, and language tasks. While complete callosotomy patients showed the expected behavioral disconnection effects-performing poorly on tasks requiring inter-hemispheric integration but well on intra-hemispheric ones-the partial callosotomy patient with a preserved portion of the splenium showed no disconnection effects across all tasks. The splenium is traditionally implicated in visual transfer, yet our findings show that minimal splenial preservation maintains functional integration across multiple perceptual and cognitive domains. This is at odds with the presumed topographical organization of the corpus callosum, suggesting a broader inter-hemispheric integrative capacity of the posterior callosal fibers. Structure-function relationships in brain networks are known to be complex and nonlinear-these findings provide novel insights into flexible structural mechanisms for inter-hemispheric communication enabling a variety of integrated behaviors.
... The earliest hypotheses on the function of the human CC came from studies of split-brain patients, subjects whose CC was partially or completely resected to prevent the diffusion of epileptic seizures (Gazzaniga, 2000(Gazzaniga, , 2005. Patients with total or partial resection involving the posterior CC suffered from disconnection syndrome (Geschwind, 1965a,b;Berlucchi, 2014), whereas in those with partial anterior resection, the disconnection could be evidenced only by specific tests (Gordon et al., 1971;Berlucchi, 2012). The emerging idea is that the CC connects the cerebral hemispheres and provides interhemispheric integration and information transfer. ...
... Thus, the posterior areas with maintained callosal SC act as hubs between widely separated regions in the posterior and anterior parts of the brain. These findings help to explain the absence of disconnection syndrome after partial callosotomy, where interhemispheric information transfer remains when the splenium is spared (Gordon et al., 1971). ...
Introduction
Functional connectivity (FC) is defined in terms of temporal correlations between physiological signals, which mainly depend upon structural (axonal) connectivity; it is commonly studied using functional magnetic resonance imaging (fMRI). Interhemispheric FC appears mostly supported by the corpus callosum (CC), although several studies investigating this aspect have not provided conclusive evidence. In this context, patients in whom the CC was resected for therapeutic reasons (split-brain patients) provide a unique opportunity for research into this issue. The present study was aimed at investigating with resting-state fMRI the interhemispheric FC in six epileptic patients who have undergone surgical resection of the CC.
Methods
The analysis was performed using fMRI of the Brain Software Library; the evaluation of interhemispheric FC and the recognition of the resting-state networks (RSNs) were performed using probabilistic independent component analysis.
Results
Generally, bilateral brain activation was often observed in primary sensory RSNs, while in the associative areas, such as those composing the default mode and fronto-parietal networks, the activation was often unilateral.
Discussion
These results suggest that even in the absence of the CC, some interhemispheric communication is still present. This residual FC might be supported through extra-callosal pathways that are likely subcortical, making it possible for some interhemispheric integration. Further studies are needed to confirm these conclusions.
... The main consequence of split-brain surgery is the specific nature of the types of information that can and cannot be transferred between the two hemispheres after the lesion (Gazzaniga and Freedman 1973). Gordon et al. in 1971 andthen Gazzaniga andFreedman in 1973 tested patients with partial callosal lesions. These studies (Gazzaniga and Freedman 1973;Gordon et al. 1971) confirmed by the recent literature (Fabri et al. 2014) revealed the functional specificity and topographical organisation of the CC. ...
... Gordon et al. in 1971 andthen Gazzaniga andFreedman in 1973 tested patients with partial callosal lesions. These studies (Gazzaniga and Freedman 1973;Gordon et al. 1971) confirmed by the recent literature (Fabri et al. 2014) revealed the functional specificity and topographical organisation of the CC. Damage to particular callosal regions blocks the transfer of specific kinds of information. ...
Autism spectrum disorder (ASD) is characterised by difficulties with social communication, interaction, and repetitive and stereotypical patterns of behaviour. Recent studies suggest that abnormalities in the corpus callosum (CC) can produce autistic symptoms, so this cerebral structure is a target for autism research. It is the largest area of white matter fibre that connects the cerebral hemispheres and has been considered an index of interhemispheric connectivity. The poor connectivity that is a characteristic of autism could be due to CC abnormalities. In this review, we describe empirical studies that have used functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to investigate the role of the CC in functional and structural brain connectivity in individuals with ASD. Establishing the anatomical correlates of abnormal connectivity in ASD is a major objective of structural and functional connectivity studies. Reduced CC volume is one of the most consistent findings in studies of autistic brains. Structural connectivity studies have shown that the CC is generally altered in ASD. In addition, functional connectivity studies show atypical activity in individuals with ASD during social cognition tasks, working memory tasks, and tests of executive function. Research on functional and structural connectivity has contributed to understanding the role of the CC in the clinical symptoms and social and cognitive deficits associated with ASD.
... La selección del paciente es de extrema importancia. Está descrito que las crisis astáticas son la mejor indicación (Gordon, et al., 1971;Andermann, et al., 1987;Fuiks, et al., 1991;Engel, et al., 1993;Reutens, et al., 1993;Tanriverdi, et al., 2009;Chambers & Bowen, 2013). Reutens (Reutens, et al., 1993) encontró en adultos y niños que las crisis astáticas era el tipo de crisis que más mejoraba, y que también existía efecto benéfico en crisis parciales complejas de origen frontal. ...
... El síndrome de desconexión sensorial o split-brain syndrome es el efecto neurofisiologico más evidente. Sin embargo, es un fenómeno que se ha evitado con la realización de callosotomías de los dos tercios anteriores dejando para un segundo tiempo quirúrgico el tercio posterior (Gordon, et al., 1971). También en el post-operatorio se puede observar un síndrome frontal con mutismo, apraxia de la marcha o incontinencia. ...
Compilación de aspectos relevantes de la epilepsia en la infancia y la adolescencia.
La epilepsia es un trastorno del cerebro que se caracteriza por una predisposición
duradera para generar ataques epilépticos (Fisher et al. 2005). 1-2 % de la población
sufre epilepsia, y en Guatemala este índice representa aproximadamente 300,000 personas,
que a diferencia de otras enfermedades crónicas, va acompañada de un fuerte
grado de marginación, discriminación y estigmatización, condiciones que repercuten
en la calidad de vida de los enfermos y sus familias, ocasionando frecuentemente más
daño que la enfermedad misma.
La importancia de la epilepsia, su diagnóstico y tratamiento apropiados, reviste cada
día mayor importancia, es por ello que HUMANA y su equipo de académicos se complace
en presentar a usted esta obra que cuenta con la participación de autores internacionales
muy destacados en el ámbito del estudio de estas enfermedades.
En esta oportunidad hemos querido enfocar nuestra atención en algunos aspectos de
relevancia en la epilepsia en la infancia y adolescencia.
Iniciamos nuestro recorrido por este apasionante mundo con un interesante trabajo
de los profesores Carla Scorza y Esper Cavalheiro, que ayudan a entender "como un
cerebro sano se vuelve epiléptico: epileptogénesis" y a conocer, "cómo y por qué los
cerebros epilépticos presentan apariencia de dinámica normal la mayor parte del
tiempo y a continuación, cambian de forma espontánea del estado interictal a estado
ictal: ictiogenesis".
Sabemos que las epilepsias tienen causas genéticas, estructurales y metabólicas y
dentro de las estructurales en niños adquieren gran relevancia las displasias, un diagnóstico
difícil para el ojo inexperto, por lo que se hace conveniente para el lector
revisar los diferentes criterios para su clasificación patológica, Es difícil tratar de
entender estas patologías sin comprender los cambios que se dan a nivel de la morfología
y organización microscópica de las estructuras involucradas; de tal manera,
el aporte de los profesores Orlando Rodas y Victor Cifuentes, nos ilustran al respecto
con un amplio estudio de los hallazgos histopatológicos observados en las displasias
corticales.
Para tratar esta enfermedad de la mejor manera tenemos que entenderla, porque sabemos
que aún con el grado de desarrollo actual y con la introducción en años resientes
de tantas nuevas moléculas, se ha mejorado el porcentaje de pacientes con
efectos secundarios, pero se ha modificado muy poco el porcentaje de pacientes farmacológicamente
refractarios (30%); además, es importante conocer y reconocer primero
que la epilepsia mata, conocer que hay daños progresivos que ponen en riesgo
la vida del paciente por no tratar adecuadamente la enfermedad, para no caer en el
conformismo de lograr resultados parciales y no tomar alternativas a tiempo; de tal
manera, la profesora Reyna Durón y su equipo nos exponen las diferentes líneas de
investigación sobre el riesgo de muerte súbita en epilepsia.
VI
Además de los cambios histopatológicos, la epilepsia en la infancia y adolescencia
involucra una serie de cambios funcionales los cuales son abordados con mestría por
nuestro querido amigo, el profesor Jorge Martínez Cerrato y su grupo de estudio.
Para el adecuado diagnóstico de la epilepsia es necesario el estudio de neuroimágenes,
que nos dan la oportunidad de observar y ubicar diferentes cambios estructurales
macroscópicos que sustentan a estas patologías, con tal propósito dos destacados
profesores Charles Akos y Linda Leary nos ilustran de forma magistral las alteraciones
observadas con el uso de imágenes cerebrales.
La epilepsia en la infancia y adolescencia incluye una serie de síndromes encefalopáticos
con características propias los cuales es necesario conocer para poder identificarlos
en la clínica con la ayuda de las herramientas apropiadas; la profesora Elza
Marcia Yacubian nos guía en este recorrido por las encefalopatías epilépticas.
Hay pocas publicaciones que correlacionan los efectos de las conductas de la sociedad
en el paciente epiléptico, como por ejemplo en la escuela; en tal sentido, el profesor
Raúl Cardona y su equipo, nos presentan una interesante revisión donde nos hacen
ver los mitos y realidades que debería saber todo clínico y maestro y por su puesto
padre de familia de un niño epiléptico.
Las epilepsias con puntas centro-temporales y las epilepsias reflejas son importantes
por su frecuencia e impacto para el pronóstico clínico por lo que en esta publicación
los profesores Jorge León, en el caso del espectro de las epilepsias con puntas centrotemporales
y sus trastornos asociados; y la profesora Eleonora Vega, con su interesante
aporte sobre las epilepsias reflejas, les han dado un espacio relevante al
estudio de estas alteraciones.
Los lineamientos actuales para el desarrollo de dietas apropiadas para todos los pacientes
epilépticos, como los son las dietas de bajo índice glicémico y las dietas especiales
como la dieta cetogénica son puntos de discusión desarrollados ampliamente
por la Licenciada Mary Jane Cordero.
El entorno social, las patologias psiquiátricas asociadas, la interacción familiar pueden
condicionar conductas y fenómenos que son confundidos con fenómenos epilépticos
sin serlo y, que por lo tanto, resultan refractarios a los tratamientos convencionales,
así el profesor Alvaro Jerez y su grupo de estudio, nos describen la naturaleza
de los mismos, sus características y probables antecedentes condicionantes y nos recuerda
la necesidad de establecer un protocolo adecuado para el diagnóstico de las
pseudocrisis por la importancia que tiene el etiquetar a un paciente así.
Finalmente saber ¿Cómo? ¿Cuándo? y ¿Por qué? se debe indicar una cirugía para
epilepsia en el paciente pediátrico, es el objetivo definido para el grupo del profesor
Juan Carlos Lara, con la idea que el lector tenga en consideración la alternativa para
cambiar a tiempo el pronóstico de un niño y su familia.
En nombre del grupo de expertos que han dado su esfuerzo desinteresado para llevar
esta obra a feliz término, los editores que coordinamos este esfuerzo esperamos que
sea de su agrado y sea de utilidad para sus pacientes, fin último de todo este esfuerzo
... Sperry and his colleagues found that anterior commissure and TCC, carried out in a single operation, almost completely controlled generalized convulsions for long periods of time. Additionally, Sperry believed verbal intelligence, numeracy, established motor coordination, personality, and temperament were not damaged by commissurotomy (Blume, 1984;Gordon et al., 1971;Sperry, 1974). Since the 1990s, CC procedures have gradually become standardized. ...
Background:
Corpus callosotomy (CC) is appropriate for patients with seizures of a bilateral or diffuse origin, or those with seizures of a unilateral origin with rapid spread to the contralateral cerebral hemisphere. The efficiency of CC in patients with drug-resistant epilepsy is a long-term concern because most articles reporting the surgical results of CC arise from small case series, and the durations of follow-up vary.
Methods:
PubMed, Embase, Cochrane Library, and Web of Science were searched to identify papers published before November 8, 2021. The systematic review was completed following PRISMA guidelines. Outcomes were analyzed by meta-analysis of the proportions.
Results:
A total of 1644 patients with drug-resistant epilepsy (49 retrospective or prospective case series studies) underwent CC, and the follow-up time of all patients was at least 1 year. The rate of complete seizure freedom (SF) was 12.38% (95% confidence interval [CI], 8.17%-17.21%). Meanwhile, the rate of complete SF from drop attacks was 61.86% (95% CI, 51.87%-71.41%). The rates of complete SF after total corpus callosotomy (TCC) and anterior corpus callosotomy (ACC) were 11.41% (95% CI, 5.33%-18.91%) and 6.75% (95% CI, 2.76%-11.85%), respectively. Additionally, the rate of complete SF from drop attacks after TCC was significantly higher than that after ACC (71.52%, 95% CI, 54.22%-86.35% vs. 57.11%, 95% CI, 42.17%-71.49%). The quality of evidence for the three outcomes by GRADE assessment was low to moderate.
Conclusion:
There was no significant difference in the rate of complete SF between TCC and ACC. TCC had a significantly higher rate of complete SF from drop attacks than did ACC. Furthermore, CC for the treatment of drug-resistant epilepsy remains an important problem for further investigation because there are no universally accepted standardized guidelines for the extent of CC and its benefit to patients. In future research, we will focus on this issue.
... The earliest hypotheses on the function of the human CC came from studies of split-brain patients, subjects whose CC was partially or completely resected to prevent the diffusion of epileptic seizures (Gazzaniga, 2000(Gazzaniga, , 2005. Patients with total or partial resection involving the posterior CC suffered from disconnection syndrome (Geschwind, 1965a(Geschwind, , 1965bBerlucchi, 2014) whereas in those with partial anterior resection the disconnection could be evidenced only by specific tests (Gordon et al., 1971;Berlucchi, 2012). ...
The concept of a topographical map of the corpus callosum (CC), the main interhemispheric commissure, has emerged from human lesion studies and from anatomical tracing investigations in other mammals. Over the last few years, a rising number of researchers have been reporting functional magnetic resonance imaging (fMRI) activation in also the CC. This short review summarizes the functional and behavioral studies performed in groups of healthy subjects and in patients undergone to partial or total callosal resection, and it is focused on the work conducted by the authors. Functional data have been collected by diffusion tensor imaging and tractography (DTI and DTT) and functional magnetic resonance imaging (fMRI), both techniques allowing to expand and refine our knowledge of the commissure. Neuropsychological test were also administered, and simple behavioral task, as imitation perspective and mental rotation ability, were analyzed. These researches added new insight on the topographic organization of the human CC. By combining DTT and fMRI it was possible to observe that the callosal crossing points of interhemispheric fibers connecting homologous primary sensory cortices, correspond to the CC sites where the fMRI activation elicited by peripheral stimulation was detected. In addition, CC activation during imitation and mental rotation performance was also reported. These studies demonstrated the presence of specific callosal fiber tracts that cross the commissure in the genu, body, and splenium, at sites showing fMRI activation, consistently with cortical activated areas. Altogether, these findings lend further support to the notion that the CC displays a functional topographic organization, also related to specific behavior.
... In these patients, complete corpus callosotomy was selected over anterior two-thirds callosotomy because of the abundance of reports suggesting that outcomes are superior for atonic seizures after single-stage complete corpus callosotomy, despite reports of lower incidence of disconnection syndromes and neuropsychological deficits in anterior two-thirds callosotomy. 3,[29][30][31][32][33][34][35][36][37] The final decision on extent of callosotomy is made at our multidisciplinary conference with input from neuropsychology on whether a patient's preoperative level of function predicts a meaningful loss of function with a complete callosotomy. ...
BACKGROUND
Magnetic resonance imaging (MRI)-guided stereotactic laser interstitial thermal therapy (LITT) is a minimally invasive technique that has been described for the treatment of certain forms of epilepsy through partial or complete callosotomy, with few cases describing single-stage complete LITT callosotomy. The authors aimed to demonstrate this technique’s feasibility and efficacy through description of the technique and 1-year outcomes in 3 cases of single-stage complete LITT callosotomy in patients with anatomically normal corpa callosa (CCs).
OBSERVATIONS
The patients were aged 14–27 years and experienced atonic seizures. Completeness of callosotomy was determined from MRI scans obtained >3 months after LITT procedures. The estimated ablations of the CC were 94%, 89%, and 100%, respectively. The second patient had a catheter breach the lateral ventricle, resulting in the lowest estimated percentage of ablation in this series (89%), with minimal atonic seizure reduction. The first patient had significant reduction in atonic seizure frequency, and the third patient had complete resolution of atonic seizures. None of the patients experienced any long-term complications. Intensive care length of stay was 1 night for each patient, and total length of stay was between 2 and 7 nights. Postoperative follow-up was between 14 and 18 months.
LESSONS
Complete laser callosotomy is achievable and is a safe alternative to microsurgical or endoscopic approaches.
... 4 Since then, commissurotomies in addition to CC have been reported from the 1960s to 1970s. 5,6 By contrast, Wilson et al 7 limited the procedure to CC alone because the role of commissural fibers other than the corpus callosum in epilepsy propagation is yet elucidated. To date, no clear evidence exists regarding which commissurotomy should be performed. ...
Background:
Corpus callosotomy (CC) is a palliative neurosurgical procedure for patients with intractable epilepsy and without resectable focal epileptogenic lesions. Anterior commissurotomy (AC) has been historically performed with CC. However, the efficacy and safety of adding AC to CC remain unknown.
Objective:
To describe the surgical technique of extraventricular AC and retrospectively investigate its clinical efficacy and safety by assessing patients who underwent CC with and without AC.
Methods:
AC has been added to CC at our institution since 2018. Fifty-five consecutive patients who received total callosotomy from 2016 to 2020 were included and categorized into 2 groups: 26 patients with additional AC and 29 patients without additional AC. Seizure outcome 1 year after surgery were compared between groups for assessing the efficacy of adding AC. The perioperative factors were compared for assessing the safety and feasibility.
Results:
Seizure reduction rate (50% and 60%; P = .60) and disappearance of drop attacks (42% and 58%; P = .25) were not significantly different between CC and CC + AC groups. No statistical group differences were found in intraoperative estimated blood loss, number of days to first oral intake, duration of postoperative intravenous hydration, and length of hospital stay.
Conclusion:
Disconnection of the anterior commissure is a feasible and relatively safe procedure. This study failed to show the significant efficacy of adding AC to CC. However, further investigation is needed to prove its efficacy in ameliorating epilepsy.
... Compared with total CC, acute and chronic disconnection syndromes have been found to be less and milder in patients where CC surgery spared the posterior portion of the corpus callosum [23]. Fiber tract studies using magnetic resonance imaging (MRI) have shown that the posterior corpus callosum transfers perceptual information [24]. ...
In 1940, van Wagenen and Herren first proposed the corpus callosotomy (CC) as a surgical procedure for epilepsy. CC has been mainly used to treat drop attacks, which are classified as generalized tonic or atonic seizures. Epileptic spasms (ESs) are a type of epileptic seizure characterized as brief muscle contractions with ictal polyphasic slow waves on an electroencephalogram and a main feature of West syndrome. Resection surgeries, including frontal/posterior disconnections and hemispherotomy, have been established for the treatment of medically intractable ES in patients with unilaterally localized epileptogenic regions. However, CC has also been adopted for ES treatment, with studies involving CC to treat ES having increased since 2010. In those studies, patients without lesions observed on magnetic resonance imaging or equally bilateral lesions predominated, in contrast to studies on resection surgeries. Here, we present a review of relevant literature concerning CC and relevant adaptations. We discuss history and adaptations of CC, and patient selection for epilepsy surgeries due to medically intractable ES, and compared resection surgeries with CC. We propose a surgical selection flow involving resection surgery or CC as first-line treatment for patients with ES who have been assessed as suitable candidates for surgery.
... [33][34][35] Neuropsychological studies of patients with callosotomies in the 1970s determined that sectioning of the anterior callosum through the isthmus but sparing the splenium resulted in fewer deficits than with complete callosal sectioning. [36][37][38] Thus, anterior callosotomy sparing the splenium is generally the preferred initial approach, with posterior callosotomy being reserved for patients with persistent seizures or for patients with relatively poor baseline functional status. ...
OBJECTIVE
Several small series have described stereotactic MRI-guided laser interstitial thermal therapy for partial callosotomy of astatic and generalized tonic-clonic (GTC) seizures, especially in association with Lennox-Gastaut syndrome. Larger case series and comparison of distinct stereotactic methods for stereotactic laser corpus callosotomy (SLCC), however, are currently lacking. The objective of this study was to report seizure outcomes in a series of adult patients with epilepsy following anterior, posterior, and complete SLCC procedures and to compare the results achieved with a frameless stereotactic surgical robot versus direct MRI guidance frames.
METHODS
The authors retrospectively reviewed sequential adult epilepsy surgery patients who underwent SLCC procedures at a single institution. They describe workflows, stereotactic errors, percentage disconnection, hospitalization durations, adverse events, and seizure outcomes after performing anterior, posterior, and complete SLCC procedures using a frameless stereotactic surgical robot versus direct MRI guidance platforms.
RESULTS
Thirteen patients underwent 15 SLCC procedures. The median age at surgery was 29 years (range 20–49 years), the median duration of epilepsy was 21 years (range 9–48 years), and median postablation follow-up was 20 months (range 4–44 months). Ten patients underwent anterior SLCC with a median 73% (range 33%–80%) midsagittal length of callosum acutely ablated. Following anterior SLCC, 6 of 10 patients achieved meaningful (> 50%) reduction of target seizures. Four patients underwent posterior (completion) SLCC following prior anterior callosotomy, and 1 patient underwent complete SLCC as a single procedure; 3 of these 5 patients experienced meaningful reduction of target seizures. Overall, 8 of 10 patients in whom astatic seizures were targeted and treated by anterior and/or posterior SLCC experienced meaningful improvement. SLCC procedures with direct MRI guidance (n = 7) versus a frameless surgical robot (n = 8) yielded median radial accuracies of 1.1 mm (range 0.2–2.0 mm) versus 2.4 mm (range 0.6–6.1 mm; p = 0.0011). The most serious adverse event was a clinically significant intraparenchymal hemorrhage in a patient who underwent the robotic technique.
CONCLUSIONS
This is the largest reported series of SLCC for epilepsy to date. SLCC provides seizure outcomes comparable to open surgery outcomes reported in the literature. Direct MRI guidance is more accurate, which has the potential to reduce the risks of SLCC. Methodological advancements and larger studies are needed.
... 53 It was observed that most of the symptoms of both acute and chronic disconnection syndrome were absent in patients in whom the posterior one third of the corpus callosum, including the splenium, was spared. 54,55 This finding led Bogen and Vogel to develop the surgical technique of partial commissurotomy to reduce the effects of dissociation symptoms. Although the complete disconnection divided the corpus callosum in its entirety, including the anterior commissure, the hippocampal commissure, fornix, and in some patients, the massa intermedia; the more limited partial commissurotomy was restricted to the anterior one third of the callosum, the anterior commissure, and 1 fornix. ...
Corpus callosotomy, first employed in the management of epilepsy by William P. van Wagenen in 1940, was for years a contentious procedure. Two decades later, Nobel Laureate Roger W. Sperry’s split-brain studies inspired surgeons to reexamine the role of corpus callosotomy in the control of epileptic seizures. In 1962, Joseph Bogen and Philip Vogel performed complete corpus callosotomies in patients with a history of generalized seizures. The identification of a set of post-surgical disconnection symptoms and other neurological deficits begged the improvement of the surgical technique. Modifications to the operation including anterior callosotomy, posterior callosotomy, partial callosotomy, staged callosotomy, microsurgical techniques, and radiosurgical techniques continue to refine the procedure.
... Thus, the posterior areas with maintained callosal structural connectivity act as hubs between widely separated regions in posterior and anterior parts of the brain. These findings help to explain the absence of disconnection syndrome after partial callosotomy where interhemispheric information transfer remains when the splenium is spared (36). ...
Significance
The relation between structural and functional connectivity has profound implications for our understanding of cerebral physiology and cognitive neuroscience. Yet, this relation remains incompletely understood. Cases in which the corpus callosum is sectioned for medical reasons provide a unique opportunity to study this question. We report functional connectivity assessed before and after surgical section of the corpus callosum, including multiyear follow-up in a limited subsample. Our results demonstrate a causal role for the corpus callosum in maintaining functional connectivity between the hemispheres. Additionally, comparison of results obtained in complete vs. partial callosotomy demonstrate that polysynaptic connections also play a role in maintaining interhemispheric functional connectivity.
... However, we believe that partial anterior callosal bisection as a means of surgical intervention in some patients with medically refractory generalized seizures not amenable to localized excisional surgery receives some support from our study. The findings of ready lateralization of generalized convulsive seizures by partial anterior callosal bisection, preservation of the posterior part of the corpus callosum enabling the prevention of the undesirable disconnection syndrome (Gordon et at., 1971), and evidence of the powerful transhemispheric seizure suppressive effect mediated through the subcortical route in the absence of the corpus callosum to another hemisphere from repeated seizures originating in one hemisphere, are all encouraging. The development of clinical criteria for case selection and determination of the exact extent and location of such partial bisection remain challenges, particularly since we do not have appropriate experimental models for many severe cases of human epilepsies. ...
Development of the centrencephalic concept in the study of epilepsy was guided by extensive electrographic and clinical observations by the Montreal school, which excelled in excising the focal cortical area of epileptogenesis (Penfield and Jasper, 1954). This theory attempted to explain generalized seizures by postulating that an epileptogenic “focus” existed in a hypothetical network of neurons in the higher brainstem near the midline, having equal and close to-and-fro interconnections with widespread cerebral cortical areas of both hemispheres by virtue of its central location. Penfield and Jasper were careful to state that they did not envisage the “centrencephalon” in anatomical terms and they emphasized further the importance of cortico-subcortico-cortical interaction for electroclinical manifestations of generalized seizures. This theory was convenient and useful in explaining generalized 3/sec spike and wave discharges as well as for explaining the secondary bilateral synchrony frequently resulting from lateralized pathophysiology.
... Callosotomy for drop attacks can either be incomplete, usually aimed at the anterior part of the corpus callosum, or complete in which the full length of the corpus callosum is transected. The rationale behind an anterior-only disconnection is the prevention of the feared disconnection syndrome (Gordon et al. 1971;Bogen 1993). When insufficient seizure control is obtained after anterior section, a completion of the callosal disconnection can be performed. ...
Precise anatomical knowledge of the structure of the corpus callosum is important in split-brain research and during neurosurgical procedures sectioning the callosum. According to the classic literature, commissural fibers connecting the motor cortex are situated in the anterior part of the corpus callosum. On the other hand, more recent imaging studies using diffusion tensor imaging indicate a more posterior topography of callosal fibers connecting motor areas. Topographical knowledge is especially critical when performing disconnective callosotomies in epilepsy patients who experience sudden loss of leg motor control, so-called epileptic drop attacks. In the current study, we aim to precisely delineate the topography of the leg motor connections of the corpus callosum. Of 20 hemispheres obtained at autopsy, 16 were dissected according to Klingler's fiber dissection technique to study the course and topography of callosal fibers connecting the most medial part of the precentral gyrus. Fibers originating from the anterior bank of the central sulcus were invariably found to be located in the isthmus of the corpus callosum, and no leg motor fibers were found in the anterior part of the callosum. The current results suggest that the disconnection of the pre-splenial fibers, located in the posterior one-third of the corpus callosum, is paramount in obtaining a good outcome after callosotomy.
... They noted that results of studies of individuals whose corpus callo- sums had been sectioned as treatment for epilepsy suggested that the splenium is of particular importance for interhemispheric transfer of a range of cognitive information. Patients in whom this region is spared suffer fewer symptoms of disconnection syndrome than do patients with complete section of the callosum or with more anterior regions of the corpus callosum or anterior commissure left intact (Gazzaniga & Freedman, 1973;Gordon et al., 1971). ...
Gonadal hormones have powerful influences on sexual differentiation of mammalian brain and behavior. This chapter evaluates the role of gonadal hormones in human neural and behavioral development. Studies of individuals who experienced prenatal hormone abnormality, because of genetic problems or because their mothers were treated with hormones during pregnancy, as well as studies relating normal variability in the early hormonal environment with normal variability in behavior, are reviewed. These studies provide substantial evidence that prenatal androgen exposure influences childhood play behavior, including toy, playmate and activity preferences, as well as sexual orientation (i.e., direction of erotic interest). Evidence also suggests influences of androgen during early development on core gender identity (the sense of self as male or female), aggressive behavior, empathy, and hand preferences. Current research activity focuses on expanding information as to the range of behaviors and psychological conditions, including psychological disorders, that are influenced by the early hormonal environment, and on identifying the mechanisms, including changes in neural structure, that underlie hormone-related behavioral changes. These findings have implications for the fundamental understanding of mechanisms of sexual differentiation of brain and behavior and of human gender development, as well as implications for clinical management of individuals with disorders of sex development.
Minimally invasive surgical techniques, such as MR-guided laser interstitial thermal therapy (LITT), have emerged as promising alternatives to open disconnective surgeries in drug-resistant epilepsy (DRE). This review synthesizes current literature on the application of LITT for corpus callosal disconnection and functional hemispheric disconnection. Studies highlight LITT's effectiveness for achieving seizure control and functional outcomes, often with reduced complications compared to traditional open procedures. Challenges include technical limitations to achieving total disconnection and adequate assessment of disconnection postoperatively. The literature is largely composed of observational studies and there is a need for rigorous, multi-center trials to establish robust guidelines and improve generalizability in clinical practice. There is also a need for a more robust exploration of how patient-specific factors contribute to response or nonresponse to intervention.
This text discusses auditory structures that are key to the central processing of auditory information. Knowledge of the neuroanatomy and neurophysiology of the central auditory nervous system (CANS) is important for health professionals and allows them to provide better guidance in patient interventions. Here we focus on one essential structure within the auditory system, the corpus callosum (CC). We recommend that the reader refer back to previous bulletins with information about other structures in the auditory system, which will allow a greater understanding of the functioning of the system as a whole. The CC is a brain structure that provides integration between the right and left cerebral hemispheres. It is considered the largest of the cerebral commissures and is made up of white matter, i.e. myelinated axons (approximately 200 million), which connect and transmit neuronal information in the cortex. The shape of this structure resembles an inverted letter 'C' (Figure 1) in sagittal section. The anterior part is made up of the knee and rostrum, the medial part is the trunk, and the posterior part is the splenium. Development takes place in an anterior-posterior direction, so the posterior portions are susceptible to damage between the 3rd trimester and birth.
Neurocognition is a substantially complex multi-component function. The corpus callosum (CC) is thought to conduct neurocognitive functions by providing communication and integration between both cerebral hemispheres. Regarding neurocognitive disorders, the changes in the CC support this argument. Exposure to anesthesia has been known to have short- and long-term effects on neurocognition. The pathophysiology of this dysfunction remains to be revealed. In this section, both the role of the CC in neurocognition and the relationship of the CC with neurocognitive disorders that develop after anesthesia exposure are discussed. Furthermore, anesthesia management is also discussed in the CC pathologies.
Infarction of the territory of the anterior cerebral artery (ACA) can be the result of carotid artery atherosclerosis and embolism, cardioembolism, local ACA atherosclerosis, or ACA dissection. Considerable variation describes the anatomy of the ACA and the brain regions it supplies. Neurologic impairments following infarction in the ACA territory include weakness, sensory loss, apraxia and callosal disconnection signs, akinetic mutism and motor neglect, language disturbance, and urinary incontinence.
Abstract Background Despite the good outcomes achieved with intravitreal angiogenic therapy, a subset of neovascular age-related macular degeneration (AMD) patients experience resistance to therapy after repeated injections. Switching drugs could offer benefit to this group of patients. Purpose To determine visual and anatomical outcomes in a cohort of neovascular AMD patients resistant to repeated injections of bevacizumab/ranibizumab after switching to aflibercept therapy. Methods This was a retrospective chart review of patients who had a diagnosis of neovascular AMD and persistent intraretinal (IRF) and/or subretinal fluid (SRF) on optical coherence tomography (OCT) for at least 3 months despite monthly bevacizumab and/or ranibizumab injections prior to transition to aflibercept. We reviewed patients’ records and OCT images obtained at baseline, 1, 3, 6 and 12 months after transition to aflibercept. Data collected included demographics, best-corrected visual acuity (BCVA), number of injections received and the occurrence of any adverse events. Studied OCT parameters included central macular thickness (CMT) values and the presence or absence of SRF, IRF and/or pigment epithelial detachment (PED) at each visit. Results We included 53 eyes of 48 patients. Mean change in BCVA from baseline was 0.05 ± 0.13 (P = 0.01) at M1, 0.04 ± 0.16 (P = 0.08) at M3, 0.01 ± 0.22 (P = 0.9) at M6, and 0.02 ± 0.28 (P = 1) at M12, while the mean change in CMT from baseline was 64 ± 75 μm (P
Generalization of sensorimotor adaptation across limbs, known as interlimb transfer, is a well-demonstrated phenomenon in humans, yet the underlying neural mechanisms remain unclear. Theoretical models suggest that interlimb transfer is mediated by interhemispheric transfer of information via the corpus callosum. We thus hypothesized that lesions of the corpus callosum, especially to its midbody connecting motor, supplementary motor, and premotor areas of the two cerebral hemispheres, would impair interlimb transfer of sensorimotor adaptation. To test this hypothesis, we recruited three patients: two rare stroke patients with recent, extensive callosal lesions including the midbody and one patient with complete agenesis. A prismatic adaptation paradigm involving unconstrained arm reaching movements was designed to assess interlimb transfer from the prism-exposed dominant arm (DA) to the unexposed non-dominant arm (NDA) for each participant. Baseline results showed that spatial performance of each patient did not significantly differ from controls, for both limbs. Further, each patient adapted to the prismatic perturbation, with no significant difference in error reduction compared with controls. Crucially, interlimb transfer was found in each patient. The absolute magnitude of each patient's transfer did not significantly differ from controls. These findings show that sensorimotor adaptation can transfer across limbs despite extensive lesions or complete absence of the corpus callosum. Therefore, callosal pathways connecting homologous motor, premotor, and supplementary motor areas are not necessary for interlimb transfer of prismatic reach adaptation. Such interlimb transfer could be mediated by transcallosal splenium pathways (connecting parietal, temporal and visual areas), ipsilateral cortico-spinal pathways or subcortical structures such as the cerebellum.
La chirurgie du troisième ventricule a toujours représenté un défit thérapeutique. Depuis
l’époque de Dandy il y’a 80 ans et jusqu'à notre époque les techniques chirurgicales à ciel
ouvert et celles spéciales représentés par la neuroendoscopie, se sont développés aidés par
les études de l’anatomie microchirurgicale de la région du V3 et les progrès de l’imagerie
médicale.
Notre travail s’est attelé à étudier les contours de la région du troisième ventricule sur le
plan anatomique et physiologique et de faire une corrélation avec les risques liés aux
différents abords chirurgicaux. Nous avons exposé aussi les différentes voies chirurgicales
ainsi que les techniques spéciales représentés par l’endoscopie et la stéréotaxie.
63 patients ont constitué notre série, nous les avons classés en quatre groupes selon le
siége de la lésion dans le V3.
Différentes techniques chirurgicales ont été réalisées dans notre série, le choix dépendait
du siége et de l’extension de la tumeur. Pour les tumeurs de la partie postérieure du V3,
nous avons réalisé dans 2/3 de ces cas une biopsie endoscopique associé à une VCS.
58 abords chirurgicaux à ciel ouvert ont été accomplis dans notre série.
Non-resective surgical strategies provide an alternative for drug-resistant patients not amenable to resective surgery due to poorly localized seizure foci, multiple foci, or epileptogenic zones co-localizing with eloquent areas carrying high risks for a resective procedure. They will not replace resective surgery, but rather complement the spectrum of surgical options. Palliative approaches comprising disconnective procedures (corpus callosotomy, CC; multiple subpial transections, MST) and neurostimulation (vagal nerve stimulation, VNS; deep brain stimulation, DBS; responsive neurostimulation, RNS) aim at reducing frequency and severity of most disabling seizures. The goal of curative non-resective surgery including ablative procedures (radiofrequency thermocoagulation, RFTC; laser-induced thermotherapy, LITT) and stereotactic radiosurgery (SRS) is to achieve complete seizure freedom as with resection. CC has been shown to reduce or abolish severe tonic or atonic drop attacks in around 90% of patients. As a stand-alone therapy, results of MST are modest with responder rates (defined as ≥50% decrease in seizure frequency) between 40% and 50%, and seizure-free outcome in 10–15% of patients. More favorable results with seizure control between 40% and 60% and responder rates between 80% and 90% can be achieved when MST are combined with resection. Neurostimulation procedures provide responder rates between 50% and 70%. Long-term assessment demonstrates continuously improving efficacy over many years suggesting a disease-modifying neuromodulation effect. With curative procedures, seizure-free outcome is achieved in 30–60% of patients. Curative stereotactic approaches can be expected to become first-line treatment options for selected patients with circumscribed lesions such as hypothalamic hamartomas, periventricular nodular heterotopias, and deep-seated focal cortical dysplasias. In addition, LITT may be considered as a minimally invasive alternative to resective surgery for mesiotemporal lobe epilepsies.
This chapter formulates seven long-standing problems related to consciousness using introspection and a certain amount of experimental evidence provided by biomedical sciences. The physical boundary problem is to find a rule that sets the boundary between our own conscious mind and the rest of the physical world. The binding problem is to explain what binds our conscious experiences into a single whole. The causal potency problem is to explain how our mind could act upon the physical world. The free will problem is to explain how it is possible for us to make genuine choices between two or more alternative future courses of action. The inner privacy problem is to explain why we have a privileged access to our unobservable conscious minds whose phenomenal content is incommunicable to others. The mind-brain relationship problem is to explain whether the mind and the brain differ, and if they do, how they interact with each other. The hard problem of consciousness is to explain how our brain generates consciousness and why we have any conscious experiences at all.
This book addresses the fascinating cross-disciplinary field of quantum information theory applied to the study of brain function. It offers a self-study guide to probe the problems of consciousness, including a concise but rigorous introduction to classical and quantum information theory, theoretical neuroscience, and philosophy of the mind. It aims to address long-standing problems related to consciousness within the framework of modern theoretical physics in a comprehensible manner that elucidates the nature of the mind-body relationship. The reader also gains an overview of methods for constructing and testing quantum informational theories of consciousness.
The complications of epilepsy surgery must include the complications from invasive procedures used in presurgical assessment as well as those arising in relation to therapeutic interventions. Intracranial electrodes have a complication rate that increases with the invasiveness and complexity of the procedure. Therapeutic procedures are divided into resective and functional operations. In resective surgery morbidity depends upon the size and site of the resection. It can be very low in non-eloquent areas such as the non-dominant frontal lobe, that is around 1% compared with greater than 30% in central and occipital regions. In the surgical management of chronic drug-resistant epilepsy, the use of interventional procedures in presurgical evaluation, and the therapeutic procedures themselves, can never be without risk of significant physical, intellectual and psychiatric complications. The impact of these complications spreads beyond the patient and surgeon to the family, referring physician, referring organization and society itself.
The failure of growth of the corpus callosum as a commissural bridge between the cerebral hemispheres is a rare condition (Ettlinger, 1977), and it is particularly rare for such individuals to grow to maturity and to be otherwise essentially normal in cognitive and neurological terms. However the systematic behavioural study of these unusual individuals may contribute to both of the issues which constituted the subtitle of this conference: namely, the “unified functioning” and “specialization” of the hemispheres.
The data that we have to report are relevant to a very straightward question, namely: Does the anterior commissure mediate useful interhemispheric transfer of visual or tactile information? Although we have routinely tested our callosotomy patients with auditory (dichotic listening) tasks as well, the absence of unihemispheric projection of auditory information from the ears makes it difficult to evaluate conclusively the presence or absence of interhemispheric transfer via the commissures. Interhemispheric transfer can be definitively tested in visual and tactile modes, however, via lateralized tachistoscopic recognition-report and unimanual tactile naming tasks, respectively. We also present some data regarding the development of right hemisphere expressive speech capability in one of our patients and of the procedures used to affirm this capacity and to refute the hypothesis of interhemispheric transfer development following callosotomy in this patient.
Die Geschichte der Epilepsiechirurgie begann am 25. 5. 1886, als Victor Horsley erstmals bei einem 22jährigen Patienten mit fokal motorischen Anfällen eine kortikale Narbe der Zentralregion operativ entfernte, die auf eine 15 Jahre zuvor erlittene Impressionsfraktur zurückging. Die Operation war erfolgreich, der Patient blieb viele Jahre anfallsfrei (Horsley 1886). Die Operation stützte sich auf die Ergebnisse experimenteller und klinischer Beobachtungen von Hughlings-Jackson und Ferrier über die zerebralen Lokalisationen, die erstmals durch elektrische Stimulation der Hirnrinde die Bedeutung des präzentralen Kortex erkannten.
The large size, central location and widespread connections of the corpus callosum stimulated, for centuries, investigations which were motivated as much by scientific curiosity as by therapeutic considerations. Callosal physiology has more recently been important to surgeons concerned primarily with other structures, including those neighboring the third ventricle, which can be approached through the corpus callosum. But the principal medical interest has been in the role of the corpus callosum in the generalization of seizures. At the end of the 19th century and on two other, separate occasions in the 20th century, callosotomy was promoted as a treatment for seizure disorders. Before 1900, less obviously around 1940, and most clearly in the 1960’s, these therapeutic proposals were stimulated by animal experimentation. One theme of this chapter is the reciprocal interaction of surgical therapy and laboratory experimentation: in particular, the most recent therapeutic use of callosotomy has been accompanied by widespread physiologic and psychologic interest in this conspicuous brain structure.
It is indeed a pleasure and an honor to be included in this symposium in commemoration of OTFRID FOERSTER. Reading over Dr. ZÜLCH’s elegant summary of FOERSTER’s interests one is reminded of the scope and influence FOERSTER had on brain research. He had, of course, a particular fascination for the problem of localization of function and it is this subject I would like to discuss as it is approached through studies on commissurotomy.
Among 55 consecutive patients with drug-refractory epileptic seizures referred to the multidisciplinary Epilepsy Program of the Medical College of Ohio for possible neurosurgical intervention for seizure control, 17 (30.90%) of those completing the multidisciplinary assessment were found to have seizure mechanisms unsuitable for treatment by focal cortical excision. Because these patients had a clear need for additional antiseizure therapy, we felt compelled to reexamine our hesitation to perform corpus callosum section (CCS) for seizure control. Viewing CCS from a background in cortical resection for seizure control, with its defined case selection criteria, known outcome probabilities for seizure control, and low neurological and neuropsychological morbidity and operative mortality (Rasmussen, 1975; Talairach et al., 1974), we experienced concern over (1) the neuropsychological consequences of callosal commisurotomy (e.g., Gazzaniga, 1970), (2) the surgical morbidity and mortality in the early series (Van Wagenen and Herren, 1940; Akelaitis, 1941a,b, 1943; Akelaitis etal., 1942; Smith and Akelaitis, 1942; Bogen and Vogel, 1962, 1975; Bogen et al., 1965; Luessenhop, 1970; Luessenhop et al., 1970; Gordon
The failure of growth of the corpus callosum as a commissural bridge between the cerebral hemispheres is a rare condition (Ettlinger, 1977), and it is particularly rare for such individuals to grow to maturity and to be otherwise essentially normal in cognitive and neurological terms. However the systematic behavioural study of these unusual individuals may contribute to both of the issues which constituted the subtitle of this conference: namely, the “unified functioning” and “specialization” of the hemispheres.
Corpus callosotomy for medically intractable epilepsies was initially performed to prevent secondarily seizure generalization through the corpus callosum in 1940, but surgical experiences indicated that this procedure was also effective for generalized epilepsies. Corpus callosotomy has been extensively used in the past 30 years. Results to date suggest that patients with secondarily generalized epilepsy with atonic, tonic, tonic-clonic seizure appear to respond well, while patients with complex partial seizures have less favorable results except for those with frontal lobe epilepsy. However, several issues remain controversial : the criteria of patient selection, the timing of the surgery, the extent of division, and the significance of postoperative EEG changes. We reviewed the developments of corpus callosotomy and its surgical indication, and discussed the seizure control mechanisms of the corpus callosum.
Division of the corpus callosum for intractable epilepsy was first reported in 1940 (Van Wagenen and Herren, 1940). The exact number of patients included in this original series has never been clear, but it may have been as many as 27. The first ten cases were reported in some detail, but followup data were limited. Subsequent cases were the subject of several psychological studies, but additional clinical information is not available. Interest in callosal section was revived in the 1960s when Bogen and his colleagues began to report the results of their series (Bogen and Vogel, 1962, 1965, 1975; Bogen et al., 1969; Gordon et al., 1971). Clinical data and followup were given for 12 cases, but most attention was directed to the neuropsychological consequences of callosal sectioning. Following this there were several reports concerning the use of callosal section for epilepsy control (Luessenhop, 1970; Luessenhop et al., 1970), but it was not until the initial report from the Dartmouth series that detailed analysis of clinical seizure patterns and prolonged followup data became available (Wilson et al., 1975). Subsequently there have been a series of articles documenting the progressive accumulation of experience from the Dartmouth program (Wilson et al., 1977, 1978). This culminated in a recent article describing 20 patients published just after Dr. Wilson’s unfortunate death (Wilson et al., 1982). Although the Dartmouth series represents the first comprehensive effort at documenting the efficacy of corpus callosal section on seizure control, the numbers remain small and the optimum selection criteria have yet to be determined.
In recent years VOGEL and BOGEN, both neurosurgeons at the White Memorial Hospital in Los Angeles, have used surgical division of the neocommissures to treat a number of patients for intractable epilepsy. This measure was always a last effort to alleviate advancing, life-threatening convulsions and for most patients so far has brought remarkable improvements (BOGEN et al., 1965; BOGEN and VOGEL, 1962). This review is based on tests with ten of these patients, eight of whom underwent a complete commissurotomy, i.e. the corpus callosum in its entirety, the anterior and hippocampal commissure, as well as the massa intermedia (when present) were sectioned in a single operation. In the other two patients (N. F., D. M.) only a partial division of the neocommissures, including the anterior two thirds of the callosum and the anterior commissure, was performed (case histories: BOGEN, 1969; GORDON et al., 1971).
Complications of invasive procedures for presurgical assessmentTherapeutic proceduresSummary
Liepmann's interpretation of apraxia is reviewed and assessed in the light of more recent investigations. There is ample support for the three main points of his theory. 1) The left hemisphere programs the gesture and 2) controls motor activity of the right hemisphere through mid-callosal pathways. 3) Motor planning is the province of the cortex and subjacent white matter. Other aspects of Liepmann's theory appear in need of modification. While he denied the existence of centres specialized in motor planning, there are now many strands of evidence suggesting the role of the parietal cortex in evoking and organizing the motor pattern.
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