The time window for successful right-hemispheric language reorganization in children

Is an earlier onset of focal epilepsy associated with atypical language lateralization? A systematic review, meta-analysis and new data

Right and bilateral language representation is common in focal epilepsy, possibly reflecting the influence of epileptogenic lesions and/or seizure activity in the left hemisphere. Atypical language lateralization is assumed to be more likely in cases of early seizure onset, due to greater language plasticity in childhood. However, evidence for this association is mixed, with most research based on small samples and heterogenous cohorts. In this preregistered meta-analysis we examined the association between age at seizure onset and fMRI-derived language lateralization in individuals with focal epilepsy. The pooled effect size demonstrated a correlation between an earlier onset and rightward language lateralization in the total sample (r=0.1, p=.005, k=58, n=1240), with no difference in the correlation between left and right hemisphere epilepsy samples (Q=62.03, p=.302). In exploratory analyses of the individual participant data (n=1157), we demonstrated strong evidence that a logarithmic model fits the data better than a linear (BF=350) or categorical model with 6 years of age as a cut-off (BF=36). These findings indicate that there is a small but significant relationship between age at seizure onset and language lateralization. The relationship was consistent with theories of language plasticity proposing an exponential decline in plasticity over early childhood. However, given that this effect was subtle and only found in larger sample sizes, an early age at seizure onset would not serve as a good indicator of atypical language lateralization on the individual patient level.

Neural mechanisms driving speech and language recovery following childhood stroke: a scoping review

PURPOSE

This scoping review aimed to inform future research priorities by collating evidence on neural correlates of speech and language recovery following childhood stroke.

METHODS

Neuroimaging, motor speech, or language outcomes following childhood stroke (28 days to 18 years age) in the subacute to chronic community stages (care occurring after acute medical management, including inpatient and outpatient rehabilitation, and community-based programs) were identified and extracted from Medline, Embase, PsycInfo, and Clinical databases.

RESULTS

Of the 3990 studies screened, 11 met the inclusion criteria. Of the included articles, no papers formally assessed speech outcomes, 11 articles reported language outcomes through standardized testing, 11 utilized structural imaging (CT, MRI), and four reported functional neuroimaging outcomes (fMRI).

INTERPRETATION

This review revealed a rudimentary accounting of speech and language profiles in children post-stroke; limited by the use of varied and incomplete speech and language assessment batteries, inconsistent reporting of lesion locations associated with speech and language outcomes, a dearth of functional neuroimaging studies, and lack of information about speech and language function throughout the rehabilitation period, a time when the brain is most plastic and receptive to therapy. Future research should provide complete and accurate accounts of speech and language function and their neural correlates throughout rehabilitation and recovery to inform care, education, and employment planning.

The long-term negative impact of childhood stroke on language

Objectives

This study aims to investigate the long-term language outcome in children with unilateral childhood stroke in comparison to those with perinatal strokes and typically developing individuals and to explore the impact of lesion-specific modifiers.

Methods

We examined nine patients with childhood stroke, acquired between 0;2 and 16;1 years (CHILD; 3 female, median = 13.5 years, 6 left-sided), 23 patients with perinatal strokes (PERI; 11 female, median = 12.5 years, 16 left-sided), and 33 age-matched typically developing individuals (CONTROL; 15 female, median = 12.33 years). The language outcome was assessed using age-appropriate tasks of the Potsdam Illinois Test of Psycholinguistic Abilities (P-ITPA) or the Peabody Picture Vocabulary Test (PPVT). For group comparisons, study-specific language z-scores were calculated. Non-verbal intelligence was assessed using the Test of Non-verbal Intelligence (TONI-4), language lateralization with functional MRI, and lesion size with MRI-based volumetry.

Results

All four patients with childhood stroke who initially presented with aphasic symptoms recovered from aphasia. Patients with childhood stroke showed significantly lower language scores than those in the control group, but their scores were similar to those of the patients with perinatal stroke, after adjusting for general intelligence (ANCOVA, language z-score CHILD = -0.30, PERI = -0.38, CONTROL = 0.42). Among the patients with childhood stroke, none of the possible modifying factors, including lesion side, correlated significantly with the language outcome.

Conclusion

Childhood stroke, regardless of the affected hemisphere, can lead to chronic language deficits, even though affected children show a "full recovery." The rehabilitation of children and adolescents with childhood stroke should address language abilities, even after the usually quick resolution of clear aphasic symptoms.

Predictors of neurocognitive outcome in pediatric ischemic and hemorrhagic stroke

This clinical study examined the impact of eight predictors (age at stroke, stroke type, lesion size, lesion location, time since stroke, neurologic severity, seizures post-stroke, and socioeconomic status) on neurocognitive functioning following pediatric stroke. Youth with a history of pediatric ischemic or hemorrhagic stroke (n = 92, ages six to 25) underwent neuropsychological testing and caregivers completed parent-report questionnaires. Hospital records were accessed for medical history. Spline regressions, likelihood ratios, one-way analysis of variance, Welch's t-tests, and simple linear regressions examined associations between predictors and neuropsychological outcome measures. Large lesions and lower socioeconomic status were associated with worse neurocognitive outcomes across most neurocognitive domains. Ischemic stroke was associated with worse outcome in attention and executive functioning compared to hemorrhagic stroke. Participants with seizures had more severe executive functioning impairments than participants without seizures. Youth with cortical-subcortical lesions scored lower on a few measures than youth with cortical or subcortical lesions. Neurologic severity predicted scores on few measures. No differences were found based on time since stroke, lesion laterality, or supra- versus infratentorial lesion. In conclusion, lesion size and socioeconomic status predict neurocognitive outcome following pediatric stroke. An improved understanding of predictors is valuable to clinicians who have responsibilities related to neuropsychological assessment and treatments for this population. Findings should inform clinical practice through enhanced appraisals of prognosis and the use of a biopsychosocial approach when conceptualizing neurocognitive outcome and setting up support services aimed at fostering optimal development for youth with stroke.

Verb generation for presurgical mapping: Gaining specificity

Verb generation is among the most frequently used tasks in presurgical mapping. Because this task involves many processes, the overall brain effects are not specific. While it is necessary to identify the whole network involving noun comprehension or semantic retrieval and lexical selection to produce the verb, isolation of those components is also crucial. Here, we present data from four patients undergoing presurgical brain mapping. The study implied a reanalysis of magnetoencephalography data with a recategorization of the used items. It aimed to extract the task component that relies on the inferior frontal gyrus (IFG). The task could be applied with higher specificity when targeting frontal areas. For that, we based item classification on the selection demands imposed by the noun. It is a robust finding that the IFG carries out this selection and that a quantitative index can be calculated for each noun, which depends on the selection effort (Proceedings of the National Academy of Sciences of the United States of America, 1997; 94(26):14792-14797, Proceedings of the National Academy of Sciences of the United States of America, 1998; 95(26):15855-15860). Data showed focality and specificity, with a correlation between this derived index and source activations in the inferior frontal gyrus for all patients. Strikingly, we detected when the right-hemisphere homologue area was involved in the selection process in two patients showing reorganization or language right lateralization. The present data are a step towards a dissection of broad specific tasks frequently used in presurgical protocols.

Atypical language organization following perinatal infarctions of the left hemisphere is associated with structural changes in right-hemispheric grey matter

AIM

To assess how atypical language organization after early left-hemispheric brain lesions affects grey matter in the contralesional hemisphere.

METHOD

This was a cross-sectional study with between-group comparisons of 14 patients (six female, 8-26 years) with perinatal left-hemispheric brain lesions (two arterial ischemic strokes, 11 periventricular haemorrhagic infarctions, one without classification) and 14 typically developing age-matched controls (TDC) with functional magnetic resonance imaging (fMRI) documented left-hemispheric language organization (six female, 8-28 years). MRI data were analysed with SPM12, CAT12, and custom scripts. Language lateralization indices were determined by fMRI within a prefrontal mask and right-hemispheric grey matter group differences by voxel-based morphometry (VBM).

RESULTS

FMRI revealed left-dominance in seven patients with typical language organization (TYP) and right-dominance in seven patients with atypical language organization (ATYP) of 14 patients. VBM analysis of all patients versus controls showed grey matter reductions in the middle temporal gyrus of patients. A comparison between the two patient subgroups revealed an increase of grey matter in the middle frontal gyrus in the ATYP group. Voxel-based regression analysis confirmed that grey matter increases in the middle frontal gyrus were correlated with atypical language organization.

INTERPRETATION

Compatible with a non-specific lesion effect, we found areas of grey matter reduction in patients as compared to TDC. The grey matter increase in the middle frontal gyrus seems to reflect a specific compensatory effect in patients with atypical language organization.

WHAT THIS PAPER ADDS

Perinatal stroke leads to decreased grey matter in the contralesional hemisphere. Atypical language organization is associated with grey matter increases in contralesional language areas.

Holistic processing and face expertise after pediatric resection of occipitotemporal cortex

The nature and extent of hemispheric lateralization and its potential for reorganization continues to be debated, although there is general agreement that there is a right hemisphere (RH) advantage for face processing in human adults. Here, we examined face processing and its lateralization in individuals with a single preserved occipitotemporal cortex (OTC), either in the RH or left hemisphere (LH), following early childhood resection for the management of drug-resistant epilepsy. The matched controls and those with a lesion outside of OTC evinced the standard superiority in processing upright over inverted faces and the reverse sensitivity to a nonface category (bicycles). In contrast, the LH and the RH patient groups were significantly less accurate than the controls and showed mild orientation sensitivities at best (and not always in the predicted directions). For the two patient groups, the accuracies of face and bicycle processing did not differ from each other and were not obviously related to performance on intermediate level global form tasks with, again, poorer thresholds for both patient groups than controls and no difference between the patient groups. These findings shed light on the complexity of hemispheric lateralization and face and nonface object processing in individuals following surgical resection of OTC. Overall, this study highlights the unique dynamics and potential for plasticity in those with childhood cortical resection.

Implications of age at lesion onset for neuropsychological outcomes: A systematic review focusing on focal brain lesions

Theories of the relation between age at lesion onset and outcomes posit different views of the young brain: resilient and plastic (i.e., the so-called "Kennard Principle"), or vulnerable (i.e., the Early Vulnerability Hypothesis). There is support for both perspectives in previous research and questions about the "best" or "worst" times to sustain brain injury remain. Here, we present a systematic review investigating the influence of age at focal brain lesion onset on cognitive functioning. This systematic review identifies and qualitatively synthesizes empirical studies from 1985 to 2021 that investigated age at lesion onset as a variable of interest associated with neuropsychological outcomes. A total of 45 studies were identified from PubMed, PsycINFO, and CINAHL databases. Almost all studies indicated that brain injury earlier in the developmental period predicts worse cognitive outcomes when compared to onset either later in the developmental period or in adulthood. More specifically, the overwhelming majority of studies support an "earlier is worse" model for domains of intellect, processing speed, attention and working memory, visuospatial and perceptual skills, and learning and memory. Relatively more variability in outcomes exists for domains of language and executive functioning. Outcomes for all domains are influenced by various other age and injury variables (e.g., lesion size, lesion laterality, chronicity, a history of epilepsy). Continued interdisciplinary understanding and communication about the influence of age at lesion onset on neuropsychological outcomes will aid in promoting the best possible outcomes for patients.

Cognitive outcome after left functional hemispherectomy on dominant hemisphere in patients with Rasmussen encephalitis: beyond the myth of aphasia. Patient series

BACKGROUND

Rasmussen encephalitis is a rare chronic neurological pathology frequently treated with functional hemispherectomy (or hemispherotomy). This surgical procedure frees patients of their severe epilepsy associated with the disease but may induce cognitive disorders and notably language alterations after disconnection of the left hemisphere.

OBSERVATIONS

The authors describe longitudinally 3 cases of female patients with Rasmussen encephalitis who underwent left hemispherotomy in childhood and benefited from a favorable cognitive outcome. In the first patient, the hemispherotomy occurred at a young age, and the recovery of language and cognitive abilities was rapid and efficient. The second patient benefited from the surgery later in childhood. In addition, she presented a reorganization of language and memory functions that seem to have been at the expense of nonverbal ones. The third patient was a teenager during surgery. She benefited from a more partial cognitive recovery with persistent disorders several years after the surgery.

LESSONS

Recovery of cognitive functions, including language, occurs after left hemispherotomy, even when performed late in childhood. Therefore, the surgery should be considered as early as possible to promote intercognitive reorganization.

Long-Term Functional Outcome Following Left Hemispherotomy in Adults and Pediatric Participants with Fmri Analysis

Background and Objective

Hemispherotomy surgery in adults is shrouded in doubts regarding the functional outcome. The age at surgery alone should not be the deciding factor for surgery. Language paradigms were used in functional magnetic resonance imaging (fMRI) to confirm the role played by the age at the onset of seizures to predict the postoperative functional outcome. The objective of the study was to formulate an optimal strategy for patient selection for the left-sided hemispherotomy in adults, based on functional outcome analysis.

Materials and Methods

A retrospective analysis of 20 participants (age at surgery 1-26 years) who underwent left hemispherotomy (over a 5-year period) was conducted. The language and motor functional assessments of 18 participants (13 pediatric and five adult participants; attrition of participants- two) were recorded at presentation and during follow-up visits. After approval was obtained from the Institutional Ethics Committee, 13 cooperative participants (eight pediatric and five adult participants) underwent language fMRI. Motor fMRI with both active and passive paradigms was done in 16 participants.

Results

All 18 participants with a mean follow-up of 24 months had class I seizure-free outcome. Of these 18, five were adults (mean age = 21 years, range: 18-22 years) and 13 were in the pediatric age group (mean age = 8 years, range: 2-15 years). Postoperatively, four adults retained both verbal fluency and language comprehension at a mean follow-up period of 38 months (range: 24-48 months). Their pre- and post-op language fMRI showed word generation and regional activations for semantic comprehension in the right hemisphere. The motor area activations were seen in the right hemisphere in two and in the left hemisphere in two participants. Among the pediatric participants, four (group I [n = 4/13]) who had good language outcome showed activations in the right hemisphere. In two participants (group II [n = 2/13]) who deteriorated postoperatively, the activations were in the left hemisphere. Five participants (group III [n = 5/13]) who retained the telegraphic language postoperatively had bilateral activations of semantic comprehension areas in fMRI. All 13 pediatric participants had motor area activations seen in the left hemisphere, similar to controls.

Conclusion

Left hemispherotomy can be advised to adults with comparably good postoperative language and motor outcome as in the pediatric age group, provided the weakness is acquired perinatally or below the age of 7 years. The fMRI is a valuable tool to aid in patient selection.

Language lateralization and outcome in perinatal stroke patients with different vascular types

Perinatal stroke affects child's language development and can change language lateralization. Language generation and comprehension tasks in functional magnetic resonance imaging were used to determine language lateralization in term born children with perinatal left-side arterial ischemic stroke (AIS) (n = 9, mean age (SD) 13.4 (3.1) y.) and periventricular venous infarction (PVI) (n = 12, 11.8 (2.8) y.), and in healthy right-handed controls (n = 30, 11.6 (2.6) y.). Lateralization index was calculated for the Broca and Wernicke areas and correlated with language and cognitive outcomes measured by the Kaufman Assessment Battery for Children II ed. Language outcome in children with perinatal stroke is poorer compared to healthy controls. Children with small AIS lesions and most children with PVI showed left-side language activation. Most children with large AIS lesions and one child with large PVI had language activation reorganized to the right hemisphere. Language reorganization to the unlesioned right hemisphere did not ensure normal language outcome.

Childhood stroke

Stroke is an important cause of neurological morbidity in children; most survivors have permanent neurological deficits that affect the remainder of their life. Stroke in childhood, the focus of this Primer, is distinguished from perinatal stroke, defined as stroke before 29 days of age, because of its unique pathogenesis reflecting the maternal-fetal unit. Although approximately 15% of strokes in adults are haemorrhagic, half of incident strokes in children are haemorrhagic and half are ischaemic. The causes of childhood stroke are distinct from those in adults. Urgent brain imaging is essential to confirm the stroke diagnosis and guide decisions about hyperacute therapies. Secondary stroke prevention strongly depends on the underlying aetiology. While the past decade has seen substantial advances in paediatric stroke research, the quality of evidence for interventions, such as the rapid reperfusion therapies that have revolutionized arterial ischaemic stroke care in adults, remains low. Substantial time delays in diagnosis and treatment continue to challenge best possible care. Effective primary stroke prevention strategies in children with sickle cell disease represent a major success, yet barriers to implementation persist. The multidisciplinary members of the International Pediatric Stroke Organization are coordinating global efforts to tackle these challenges and improve the outcomes in children with cerebrovascular disease.

[Hemispherotomy in pediatric epilepsy surgery-Surgical, epileptological and functional aspects]

Hemispherotomies represent a major part of surgical interventions for epilepsy in childhood (16-21%). The anatomical resection has been replaced by minimally invasive disconnection techniques with lower perioperative mortality and fewer postoperative complications. Today the procedure is not only carried out from the lateral aspect via the Sylvian fissure/insula but also via a vertical parasagittal approach. Depending on the publication, hemispherotomy leads to freedom from postoperative seizures in 60-90% of patients. Despite changes in the surgical technique, disturbances of the cerebrospinal fluid circulation continue to be the main complication in 5-15% of cases. Hemispheric epileptogenic lesions usually lead to early onset and difficult to treat epilepsy in childhood. These epilepsies are characterized by a high frequency of seizures and propagation of epileptic discharges to the healthy hemisphere. The aim of a hemispherotomy is, in addition to postoperative freedom from seizures, the complete disconnection of the affected hemisphere. When deciding on a hemispherotomy, the expected functional consequences play a major role in addition to epileptological aspects. In the case of deficits already present preoperatively (hemianopia, hemiparesis) or reorganization of functions in the contralesional hemisphere (language), no new deficits are to be expected from the operation. In terms of cognition, a hemispherotomy can improve function by releasing the neuroplastic potential of the healthy hemisphere. In order to keep the negative and often irreversible effects of epilepsy as low as possible and to be able to use as much potential for neuroplasticity of the healthy hemisphere as possible, surgery should be considered as early as possible.

Practical Aspects of Functional Magnetic Resonance Imaging in Children

Functional magnetic resonance imaging (fMRI) has become a broadly accepted presurgical mapping tool for pediatric populations with brain pathology. The aim of this article is to provide general guidelines on the pragmatic aspects of performing and processing fMRI, as well as interpreting its results across children of all age groups. Based on the author's accumulated experience of more than 20 years on this specific field, these guidelines consider many factors that include the particular physiology and anatomy of the child's brain, and how specific peculiarities may pose disadvantages or even certain advantages when performing fMRI procedures. The author carefully details the various challenges that the practitioner might face in dealing with limited volitional behavior and language comprehension of infants and small children and remedial strategies. The type and proper choice of task-based paradigms in keeping with the age and performance of the patient are discussed, as well as the appropriate selection and dosage of sedative agents and their inherent limitations. Recommendations about the scanner and settings for specific sequences are provided, as well as the required devices for appropriate stimulus delivery, response, and motion control. Practical aspects of fMRI postprocessing and quality control are discussed. Finally, given the relevance of resting-state-fMRI for use in noncooperative patients, a praxis-oriented guide to obtain, classify, and understand the spontaneous neural networks (utilizing independent component analysis) is also provided. The article concludes with a thorough discussion about the possible pitfalls at different stages of the fMRI process.

Organizing Variables Affecting fMRI Estimates of Language Dominance in Patients with Brain Tumors

Numerous variables can affect the assessment of language dominance using presurgical functional magnetic resonance (fMRI) in patients with brain tumors. This work organizes the variables into confounding and modulating factors. Confounding factors give the appearance of changed language dominance. Most confounding factors are fMRI-specific and they can substantially disrupt the evaluation of language dominance. Confounding factors can be divided into two categories: tumor-related and fMRI analysis. The tumor-related confounds further subdivide into tumor characteristics (e.g., tumor grade) and tumor-induced conditions (aphasia). The fMRI analysis confounds represent technical aspects of fMRI methods (e.g., a fixed versus an individual threshold). Modulating factors can modify language dominance without confounding it. They are not fMRI-specific, and they can impact language dominance both in healthy individuals and neurosurgical patients. The effect of most modulating factors on fMRI language dominance is smaller than that of confounding factors. Modulating factors include demographics (e.g., age) and linguistic variables (e.g., early bilingualism). Three cases of brain tumors in the left hemisphere are presented to illustrate how modulating confounding and modulating factors can impact fMRI estimates of language dominance. Distinguishing between confounding and modulating factors can help interpret the results of presurgical language mapping with fMRI.

Prior Neurosurgery Decreases fMRI Estimates of Language Laterality in Patients with Gliomas within Anterior Language Sites

The impact of previous surgery on the assessment of language dominance with preoperative fMRI remains inconclusive in patients with recurrent brain tumors. Samples in this retrospective study included 17 patients with prior brain surgery and 21 patients without prior surgery (38 patients total; mean age 43.2, SD = 11.9; 18 females; seven left-handed). All the patients were left language dominant, as determined clinically. The two samples were matched on 10 known confounds, including, for example, tumor laterality and location (all tumors affected Brodmann areas 44/45/47). We calculated fMRI language dominance with laterality indices using a whole-brain and region of interest approach (ROI; Broca’s and Wernicke’s area). Patients with prior surgery had decreased fMRI language dominance (p = 0.03) with more activity in the right hemisphere (p = 0.03) than patients without surgery. Patients with prior brain surgery did not display less language activity in the left hemisphere than patients without surgery. These results were replicated using an ROI approach in the affected Broca’s area. Further, we observed no differences between our samples in the unaffected Wernicke’s area. In sum, prior brain surgery affecting Broca’s area could be a confounding factor that needs to be considered when evaluating fMRI language dominance.

Neuroplasticity during the transition period: How the adolescent brain can recover from aphasia. A pilot study

BACKGROUND

Increasing clinical and scientific attention is given to the transition of neurological stages from child to adult. Data on brain plasticity during adolescence is interesting for providing adequate evidence-based medical attention to neurological conditions in this population. Acquired aphasia is well described in adults and children, but not in adolescence.

OBJECTIVE

We describe a 5-year follow-up of language in three adolescent subjects with post-brain injury aphasia.

METHODS

We analysed and scored formal aspects of language three times, language hemispheric dominance twice with dichotic listening test and functional magnetic resonance imaging (fMRI) brain activation patterns that supported expressive and comprehensive language during the recovery period.

RESULTS

We found similarities to both paediatric and adult aphasia in these three adolescents. While the level of recovery resembled that of children with aphasia, a more efficient language rehabilitation occurred in those who remained with left hemispheric dominance in the chronic stage, as it is reported in adults.

CONCLUSIONS

Our analysis and long-term follow-up provide data for a better understanding on how the injured brain matures during adolescence. More studies with larger samples will help to understand the function of the remaining networks and the recovery from injury in this particular age group.

Effect of corpus callosum agenesis on the language network in children and adolescents

The present study is interested in the role of the corpus callosum in the development of the language network. We, therefore, investigated language abilities and the language network using task-based fMRI in three cases of complete agenesis of the corpus callosum (ACC), three cases of partial ACC and six controls. Although the children with complete ACC revealed impaired functions in specific language domains, no child with partial ACC showed a test score below average. As a group, ACC children performed significantly worse than healthy controls in verbal fluency and naming. Furthermore, whole-brain ROI-to-ROI connectivity analyses revealed reduced intrahemispheric and right intrahemispheric functional connectivity in ACC patients as compared to controls. In addition, stronger functional connectivity between left and right temporal areas was associated with better language abilities in the ACC group. In healthy controls, no association between language abilities and connectivity was found. Our results show that ACC is associated not only with less interhemispheric, but also with less right intrahemispheric language network connectivity in line with reduced verbal abilities. The present study, thus, supports the excitatory role of the corpus callosum in functional language network connectivity and language abilities.

Signatures of brain plasticity supporting language recovery after perinatal arterial ischemic stroke

Brain imaging methods such as functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging (DTI) have already been used to decipher the functional and structural brain changes occurring during normal language development. However, little is known about the differentiation of the language network after an early lesion. While in adults, stroke over the left hemisphere generally induces post-stroke aphasia, it is not always the case when a stroke occurs in the perinatal period, thus revealing a remarkable plastic power of the language network during early development. In particular, the role of perilesional tissues, as opposed to undamaged brain areas in the functional recovery of language functions after an early insult, remains unclear. In this review article, we provide an overview of the extant literature using functional and structural neuroimaging data revealing the signatures of brain plasticity underlying near-normal language development.

Large-scale resculpting of cortical circuits in children after surgical 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.

Language after childhood hemispherectomy: A systematic review

OBJECTIVE

To conduct a systematic review on language outcomes after left and right hemispherectomy in childhood, a surgical procedure that involves removing or disconnecting a cerebral hemisphere.

METHODS

We searched MEDLINE, Embase, and PsycInfo for articles published between January 1, 1988, and May 16, 2019. We included (1) all types of observational studies; (2) studies in which hemispherectomy was performed before age 18 years; and (3) studies with standardized scores measuring receptive vocabulary, expressive vocabulary, sentence comprehension, and/or sentence production. We calculated mean z scores after left and right hemispherectomy in the whole group and within etiology-specific subgroups.

RESULTS

Our search identified 1,096 studies, of which 17 were eligible. The cohort added up to 205 individuals (62% left hemispherectomy) assessed 1 to 15 years after surgery. In the left surgery group, all language skills were impaired (z scores <-1.5) except sentence comprehension. In the right surgery group, language performance was in the borderline range (z scores ∼ -1.5). Children with cortical dysplasia showed the worst outcomes irrespective of surgery side (z scores <-2.5). Individuals with left vascular etiology and right-sided Rasmussen syndrome showed the best outcomes.

CONCLUSION

Evidence based on the largest patient cohort to date (205 participants) suggests that the risk of language impairment after hemispherectomy is high, with few exceptions. Etiology plays a major role in postsurgical plasticity. We recommend specialist evaluation of language skills soon after surgery to identify intervention targets. Large-scale studies examining outcomes in consecutive cases are still needed.

Principles of early intervention

The great majority of children with neurodevelopmental challenges do not get specific intervention until after their second birthday. This worsens their outcomes, because a great part of the entire neuroplastic window for learning is misspent. There is emerging evidence that the impact on outcomes of early goal-directed training involving the parents in infants with neurodevelopmental disabilities is significantly superior to the results achieved in older children and adults, especially if intervention commences in the first months of life. This chapter outlines the common elements of neurodevelopment and early intervention. It includes an outline of some of the primary early intervention practices and the scientific evidence driving them.

Predicting Language Outcome After Left Hemispherotomy: A Systematic Literature Review

Objective

Hemidecortication is a therapeutic option in patients with drug-resistant structural epilepsy. If surgery is performed early enough in left-hemispheric pathology, the plasticity of the developing brain may enable the right hemisphere to take over language-if this has not occurred before surgery. A systematic overview of potential predictors of language outcome after left hemidecortication in children is warranted.

Methods

In a systematic literature review, we analyzed 58 studies on language lateralization after congenital or postneonatally acquired left-hemispheric pathology, and on language outcome after left-sided hemidisconnection, such as hemispherotomy. Single-subject data were pooled to determine the distribution of lateralization across etiologies in congenital lesions and across age groups in acute postneonatal lesions. A hierarchical linear regression assessed the influence of age at surgery, lesion type, age at seizure onset, and presurgery language function on language outcome after left hemidecortication.

Results

In acute postneonatal lesions, younger age at injury was significantly associated with right-sided language lateralization (Cramér V = 0.458; p = 0.039). In patients with hemidecortication, age at surgery was not significantly associated with language outcome (Cramér V = -0.056; p = 0.584). Presurgical language function was the most powerful predictor for postsurgical language outcome (F _4,47 = 7.35, p < 0.0001), with good presurgical language bearing the risk of postsurgical deterioration. In congenital pathology, right-sided language lateralization was most frequent in pre-/perinatal stroke (Cramér V = 0.357; p < 0.0001).

Conclusions

We propose a presurgical decision algorithm with age, presurgical language function, language lateralization, and left-hemispheric structural pathology as decision points regarding surgery.

Right Structural and Functional Reorganization in Four-Year-Old Children with Perinatal Arterial Ischemic Stroke Predict Language Production

Brain imaging methods have contributed to shed light on the mechanisms of recovery after early brain insult. The assumption that the unaffected right hemisphere can take over language functions after left perinatal stroke is still under debate. Here, we report how patterns of brain structural and functional reorganization were associated with language outcomes in a group of four-year-old children with left perinatal arterial ischemic stroke (PAIS). Specifically, we gathered specific fine-grained developmental measures of receptive and productive aspects of language as well as standardized measures of cognitive development. We also collected structural neuroimaging data as well as functional activations during a passive listening story-telling fMRI task and a resting state session (rs-fMRI). Children with a left perinatal stroke showed larger lateralization indices of both structural and functional connectivity of the dorsal language pathway towards the right hemisphere that, in turn, were associated with better language outcomes. Importantly, the pattern of structural asymmetry was significantly more right-lateralized in children with a left perinatal brain insult than in a group of matched healthy controls. These results strongly suggest that early lesions of the left dorsal pathway and the associated perisylvian regions can induce the interhemispheric transfer of language functions to right homolog regions. This study provides combined evidence of structural and functional brain reorganization of language networks after early stroke with strong implications for neurobiological models of language development.

Perinatal stroke syndromes: Similarities and diversities in aetiology, outcome and management

With a birth-prevalence of 37-67/100,000 (mostly term-born), perinatal stroke encompasses distinct disease-states with diverse causality, mechanism, time of onset, mode of presentation and outcome. Neonatal primary haemorrhagic stroke and ischemic events (also divided into neonatal arterial ischemic stroke and neonatal cerebral sinus venous thrombosis) that manifest soon after birth are distinguished from presumed perinatal - ischemic or haemorrhagic - stroke. Signs of the latter become apparent only beyond the neonatal period, most often with motor asymmetry or milestones delay, and occasionally with seizures. Acute or remote MRI defines the type of stroke and is useful for prognosis. Acute care relies on homeostatic maintenance. Seizures are often self-limited and anticonvulsant agents might be discontinued before discharge. Prolonged anticoagulation for a few weeks is an option in some cases of sinovenous thrombosis. Although the risk of severe impairment is low, many children develop mild to moderate multimodal developmental issues that require a multidisciplinary approach.

Oligodendrocyte Progenitor Cell Proliferation and Fate after White Matter Stroke in Juvenile and Adult Mice

The incidence of stroke in children is 2.4 per 100,000 person-years and results in long-term motor and cognitive disability. In ischemic stroke, white matter (WM) is frequently injured, but is relatively understudied compared to grey matter injury. Previous research suggests that the cellular response to WM ischemic injury is different at different ages. Little is known about whether WM repair mechanisms differ in children and adults. We utilized a model of focal ischemic WM injury to determine the oligodendrocyte (OL) response to focal WM ischemic injury in juvenile and adult mice. Methods: Juvenile (21-25 days of age) versus adult (2-3 months of age) mice underwent stereotaxic injection of the potent vasoconstrictor N5-(1-iminoethyhl)-L-ornithine (L-NIO) into the lateral corpus callosum (CC). Animals were sacrificed on postoperative day 3 (acute) or 21 (chronic). Cell birth-dating was performed acutely after WM stroke with 5-ethynyl-2-deoxyuridine (EdU) injected intraperitoneally. Immunohistochemistry was performed, as well as stereology, to measure injury volume. The acute oligodendrocyte progenitor cell (OPC) proliferation and the chronic OL cell fate were determined with immunohistochemistry. Compound action potentials were measured in the CC at acute and chronic time points. Results: Acutely WM injury volume was smaller in juveniles. There was significantly greater OPC proliferation in juvenile animals (acute) compared to adults, but newly born OLs did not survive and mature into myelinating cells at chronic time points. In addition, juveniles did not have improved histological or functional recovery when compared to adults. Protecting newly born OPCs is a potential therapeutic target in children with ischemic stroke.

Corticobulbar Tract Injury, Oromotor Impairment and Language Plasticity in Adolescents Born Preterm

Children born preterm are at risk of impairments in oromotor control, with implications for early feeding and speech development. In this study, we aimed to identify (a) neuroanatomical markers of persistent oromotor deficits using diffusion-weighted imaging (DWI) tractography and (b) evidence of compensatory neuroplasticity using functional MRI (fMRI) during a language production task. In a cross-sectional study of 36 adolescents born very preterm (<33 weeks' gestation) we identified persistent difficulties in oromotor control in 31% of cases, but no clinical diagnoses of speech-sound disorder (e.g., dysarthria, dyspraxia). We used DWI-tractography to examine the microstructure (fractional anisotropy, FA) of the corticospinal and corticobulbar tracts. Compared to the unimpaired group, the oromotor-impaired group showed (i) reduced FA within the dorsal portion of the left corticobulbar tract (containing fibres associated with movements of the lips, tongue, and larynx) and (ii) greater recruitment of right hemisphere language regions on fMRI. We conclude that, despite the development of apparently normal everyday speech, early injury to the corticobulbar tract leads to persistent subclinical problems with voluntary control of the face, lips, jaw, and tongue. Furthermore, we speculate that early speech problems may be ameliorated by cerebral plasticity - in particular, recruitment of right hemisphere language areas.

Atypical language representation is unfavorable for language abilities following childhood stroke

Brain plasticity has often been quoted as a reason for the more favorable outcome in childhood stroke compared to adult stroke. We investigated the relationship between language abilities and language localization in childhood stroke. Seventeen children and adolescents with left- or right-sided ischemic stroke and 18 healthy controls were tested with a comprehensive neurolinguistic test battery, and the individual neural representation of language was measured with an fMRI language paradigm. Overall, 12 of 17 stroke patients showed language abilities below average, and five patients exhibited impaired language performance. fMRI revealed increased activity in right hemisphere areas homotopic to left hemisphere language regions. In sum, seven stroke patients revealed atypical, i.e. bilateral or right lateralized language representation. Typical left hemispheric language lateralization was associated with better performance in naming and word fluency, whereas increased involvement of right homologues was accompanied by worse language outcome. In contrast, lesion lateralization or lesion volume did not correlate with language outcome or atypical language lateralization. Thus, atypical language lateralization is unfavorable for language outcome, and right homologues do not have the same cognitive capacity, even in young children.

When two are better than one: Bilateral mesial temporal lobe contributions associated with better vocabulary skills in children and adolescents

This study considered the involvement of the mesial temporal lobe (MTL) in language and verbal memory functions in healthy children and adolescents. We investigated 30 healthy, right-handed children and adolescents, aged 7-16, with a fMRI language paradigm and a comprehensive cognitive test battery. We found significant MTL activations during language fMRI in all participants; 63% of them had left lateralized MTL activations, 20% exhibited right MTL lateralization, and 17% showed bilateral MTL involvement during the fMRI language paradigm. Group analyses demonstrated a strong negative correlation between the lateralization of MTL activations and language functions. Specifically, children with less lateralized MTL activation showed significantly better vocabulary skills. These findings suggest that the mesial temporal lobes of both hemispheres play an important role in language functioning, even in right-handers. Our results furthermore show that bilateral mesial temporal lobe involvement is advantageous for vocabulary skills in healthy, right-handed children and adolescents.