Hemispherectomy sustained before adulthood does not cause persistent hemispatial neglect

Listening with one hemisphere: A review of auditory processing among individuals after hemispheric surgery

The human auditory system consists of both peripheral and central components, both of which play a role but contribute distinctly to overall auditory functioning and can be differentially impacted by pathophysiologic states. Hemispheric surgery (HS), a procedure used for the treatment of drug-resistant epilepsy, involves complete disconnection of the auditory cortex in the operative hemisphere, leaving hearing acuity (peripheral function) intact but having heavy implications for auditory processing (central function). The literature describing pre- and post-operative auditory processing abilities of individuals who have undergone HS is sparse, but the research available provides evidence that several central auditory processes including auditory spatial analysis and temporal processing may be impacted. Deficits noted in standardized testing within the clinical or research environment have concrete functional impacts that may be currently under-appreciated and could lead to under-utilization of appropriate therapeutic strategies and accommodations. This review describes the profile of central auditory processing abilities in patients who have undergone HS by synthesizing available literature and incorporating research in other clinical populations to help fill critical gaps in our understanding of how cerebral disconnection impacts the central auditory system.

Space- and object-based attention in patients with a single hemisphere following childhood resection

The neural processes underlying attentional processing are typically lateralized in adults, with spatial attention associated with the right hemisphere (RH) and object-based attention with the left hemisphere (LH). Using a modified two-rectangle attention paradigm, we compared the lateralization profiles of individuals with childhood hemispherectomy (either LH or RH) and age-matched, typically developing controls. Although patients exhibited slower reaction times (RTs) compared to controls, both groups benefited from valid attentional cueing. However, patients experienced significantly higher costs for invalid trials-reflected by larger RT differences between validly and invalidly cued targets. This was true for invalid trials on both cued and uncued objects, probes of object- and space-based attentional processes, respectively. Notably, controls showed no significant RT cost differences between invalidly cued locations on cued versus uncued objects. By contrast, patients exhibited greater RT costs for targets on uncued versus cued objects, suggesting greater difficulty shifting attention across objects. We explore potential explanations for this group difference and the lack of difference between patients with LH or RH resection. These findings enhance our understanding of spatial and object-based attention in typical development and reveal how significant neural injury affects the development of attentional systems in the LH and RH.

Hemimegalencephaly: A Systematic Comparison of Functional and Anatomic Hemispherectomy for Drug-Resistant Epilepsy

BACKGROUND AND OBJECTIVES

Hemimegalencephaly (HME) is a rare diffuse malformation of cortical development characterized by unihemispheric hypertrophy, drug-resistant epilepsy (DRE), hemiparesis, and developmental delay. Definitive treatment for HME-related DRE is hemispheric surgery through either anatomic (AH) or functional hemispherectomy (FH). This individual patient data meta-analysis assessed seizure outcomes of AH and FH for HME with pharmacoresistant epilepsy, predictors of Engel I, and efficacy of different FH approaches.

METHODS

PubMed, Web of Science, and Cumulative Index to Nursing and Allied Health Literature were searched from inception to Jan 13th, 2023, for primary literature reporting seizure outcomes in >3 patients with HME receiving AH or FH. Demographics, neurophysiology findings, and Engel outcome at the last follow-up were extracted. Postsurgical seizure outcomes were compared through 2-tailed t -test and Fisher exact test. Univariate and multivariate Cox regression analyses were performed to identify independent predictors of Engel I outcome.

RESULTS

Data from 145 patients were extracted from 26 studies, of which 89 underwent FH (22 vertical, 33 lateral), 47 underwent AH, and 9 received an unspecified hemispherectomy with a median last follow-up of 44.0 months (FH cohort) and 45.0 months (AH cohort). Cohorts were similar in preoperative characteristics and at the last follow-up; 77% (n = 66) of the FH cohort and 81% (n = 38) and of the AH cohort were Engel I. On multivariate analysis, only the presence of bilateral ictal electroencephalography abnormalities (hazard ratio = 11.5; P = .002) was significantly associated with faster time-to-seizure recurrence. A number-needed-to-treat analysis to prevent 1 additional case of posthemispherectomy hydrocephalus reveals that FH, compared with AH, was 3. There was no statistical significance for any differences in time-to-seizure recurrence between lateral and vertical FH approaches (hazard ratio = 2.59; P = .101).

CONCLUSION

We show that hemispheric surgery is a highly effective treatment for HME-related DRE. Unilateral ictal electroencephalography changes and using the FH approach as initial surgical management may result in better outcomes due to significantly lower posthemispherectomy hydrocephalus probability. However, larger HME registries are needed to further delineate the predictors of seizure outcomes.

Visual neglect: does it exist in children with unilateral brain lesion? A systematic review

Visual Neglect (VN) is a common neuropsychological disorder in adults with unilateral brain lesion (UBL), characterized by the failure to attend and to report sensory events occurring in one side of space, contralateral to an area of brain damage. Less is known about VN expression in children following brain injury. The aim of this systematic review is to evaluate the presence of VN in UBL children and to identify the best neuropsychological assessment's tool for this population. A comprehensive search of 4 databases (Pubmed, Cochrane Database, SCOPUS, DARE) was undertaken from May 2020 to January 2021. Inclusion criteria were (i) subjects less than 18 years with cerebral lesions and with MRI, (ii) specific neuropsychological assessments for VN, (iii) studies published in English since 2000. A total of 309 articles were found in the initial search but only 10 observational studies met the full inclusion criteria. In these studies, 1051 subjects were evaluated for VN, of them 749 were controls and 302 had brain lesions. The two most common types of neuropsychological tools used in children with unilateral brain damage to assess the presence of VN were target cancellation tests and drawing tests.This review confirms the possibility that children with UBL can develop VN, even if it is not very clear which brain structure's characteristics can increase this risk. Children with right lesion showed visuo-spatial attention deficits focalized on the contralateral side, compatible with diagnosis of VN, while children with left lesion showed more generalized attention difficulties. The overall level of evidence correlating the presence of VN and different types of UBL in children was low and neuropsychological assessment of VN for children are sparse. Some important limitations of this review must be reported: the limited number of studies included, the administration of various types of tests to evaluate VN, the lack of information regarding the cognitive level of children in most of the studies. Further research is needed to understand patterns of VN based on brain structure and time since lesion.Systematic Review Registration: ID on PROSPERO: CRD42021281993.

Pediatric and Adult Low-Grade Gliomas: Where Do the Differences Lie?

Two thirds of pediatric gliomas are classified as low-grade (LGG), while in adults only around 20% of gliomas are low-grade. However, these tumors do not only differ in their incidence but also in their location, behavior and, subsequently, treatment. Pediatric LGG constitute 65% of pilocytic astrocytomas, while in adults the most commonly found histology is diffuse low-grade glioma (WHO II), which mostly occurs in eloquent regions of the brain, while its pediatric counterpart is frequently found in the infratentorial compartment. The different tumor locations require different skillsets from neurosurgeons. In adult LGG, a common practice is awake surgery, which is rarely performed on children. On the other hand, pediatric neurosurgeons are more commonly confronted with infratentorial tumors causing hydrocephalus, which more often require endoscopic or shunt procedures to restore the cerebrospinal fluid flow. In adult and pediatric LGG surgery, gross total excision is the primary treatment strategy. Only tumor recurrences or progression warrant adjuvant therapy with either chemo- or radiotherapy. In pediatric LGG, MEK inhibitors have shown promising initial results in treating recurrent LGG and several ongoing trials are investigating their role and safety. Moreover, predisposition syndromes, such as neurofibromatosis or tuberous sclerosis complex, can increase the risk of developing LGG in children, while in adults, usually no tumor growth in these syndromes is observed. In this review, we discuss and compare the differences between pediatric and adult LGG, emphasizing that pediatric LGG should not be approached and managed in the same way as adult LCG.

Visual Neuropsychology in Development: Anatomo-Functional Brain Mechanisms of Action/Perception Binding in Health and Disease

Vision is the main entrance for environmental input to the human brain. Even if vision is our most used sensory modality, its importance is not limited to environmental exploration. Rather it has strong links to motor competences, further extending to cognitive and social aspects of human life. These multifaceted relationships are particularly important in developmental age and become dramatically evident in presence of complex deficits originating from visual aberrancies. The present review summarizes the available neuropsychological evidence on the development of visual competences, with a particular focus on the associated visuo-motor integration skills in health and disease. With the aim of supporting future research and interventional settings, the goal of the present review is to constitute a solid base to help the translation of neuropsychological hypotheses into straightforward empirical investigations and rehabilitation/training protocols. This approach will further increase the impact, ameliorate the acceptance, and ease the use and implementation of lab-derived intervention protocols in real-life situations.

THE NEUROPHENOMENOLOGY OF OUT-OF-BODY EXPERIENCES INDUCED BY HYPNOTIC SUGGESTIONS

Inducing out-of-body experiences in hypnosis (H-OBEs) offers an almost unique opportunity to investigate them under controlled conditions. OBEs were induced as an imaginative task in a resting condition (I-OBE) or in hypnosis (H-OBE) in a group of 15 high hypnotizable subjects. A 32-channel EEG was recorded, and the spectral power and imaginary coherence of each frequency band and each couple of electrodes were calculated. At the end of each session, the Phenomenology of Consciousness Inventory (PCI) was administered to assess the phenomenological aspects of the subjects' experience. Significantly higher scores in the altered state, positive affect altered experience, and attention subdimensions of the PCI were reported in H-OBE than in I-OBE, which were associated with a significant decrease of power in beta and gamma band activity in right parieto-temporal derivations. These results suggest that the H-OBE may offer a useful experimental model of spontaneous OBEs.

Long term neurocognitive improvement after "late" right hemispherectomy: case report and review of the literature

OBJECTIVE

To study the long-term neurocognitive changes of a right-handed girl with intractable epilepsy after late right hemispherectomy and compare them with data in the literature.

METHOD

The girl was affected by an epileptic encephalopathy associated with right fronto-temporo-parietal polymicrogyria; she was submitted to right hemispherectomy at the age of 5 and examined with cognitive and neuropsychological tests at the age of 17 years. The girl took advantage of neurocognitive rehabilitation for several years; she is currently seizure-free and off therapy.

RESULTS

At the end of the follow-up, the full-scale IQ is stable and within the normal range (p = 88). As the discrepancy between verbal IQ (pp = 120) and performance IQ (pp = 71) is significantly high, the girl was subjected to neurocognitive evaluation with the following results: verbal problem solving, verbal short- and long-term memory, and executive functions are within normal range. The most fragile functional areas are visual and spatial reasoning, verbal working memory, short-term visuospatial memory, visual attention, and processing speed, all > 2 SD. The spatial tests, such as coding, matrix reasoning, picture concepts, and arithmetic reasoning (which are favored by other functions such as associative memory and learning ability), are less severely impaired.

CONCLUSIONS

These findings show that good conceptual skills and verbal reasoning can compensate for some deficits in visual-perceptual and visuospatial functions.

Auditory neglect in children following perinatal stroke

Auditory neglect has been found in adults with right hemisphere focal brain lesions following strokes. Visual and tactile neglect has been found in children following both left and right hemisphere lesions resulting from perinatal strokes. The present cross-sectional study assessed auditory neglect in children with early unilateral brain damage from perinatal stroke. Twenty-six children with perinatal stroke and matched controls participated. All were asked to identify the location of a pure tone presented in left or right auditory fields. We found that children who had experienced left hemisphere perinatal strokes were significantly better at localizing sounds on the left side of space than the right side of space, and that response times improved with age on a normal trajectory relative to controls in left hemispace, while they did not improve normally in right hemispace. Children with right hemisphere perinatal strokes were significantly worse at localizing sounds on the right side of space relative to typically developing controls, and did not follow control trajectories for improvement in response times on the left or the right sides of space. Our preliminary results suggest that left hemisphere perinatal strokes may result in contralateral auditory neglect, while right hemisphere perinatal strokes may result in bilateral auditory neglect. Neglect was more severe in children with parietal lobe involvement, suggesting that the parietal lobe may play a dominant role in auditory attention in the developing brain.

Current tests and trends in single-case neuropsychology

In this issue of Cortex, Crawford, Garthwaite and Ryan publish bayesian statistical tests that will enable researchers to take account of covariates when comparing single patients to control samples. In this article, we provide some context for this development, from an audit of the Cortex archives. We suggest that single-case research is alive and well, and more rigorous than ever, and that current practice has been shaped considerably by Crawford and colleagues' statistical refinements over the past 12 years. However, there is scope for further tightening and standardisation of statistical methods and reporting standards. The advantages offered by the new bayesian tests should promote the even wider use of appropriate statistical methods, with benefits for the validity of individual studies, and for cross-comparability in the single-case literature.

Recovery from spatial neglect and hemiplegia in a child despite a large anterior circulation stroke and Wallerian degeneration

Prognosis after stroke in children is difficult given the paucity of literature regarding motor and cognitive recovery. Spatial neglect has been described in children after stroke, yet little evidence exists to guide clinicians and parents regarding its resolution. Wallerian degeneration on magnetic resonance imaging (MRI) suggests poor recovery in neonates and adults. We report near complete resolution of spatial neglect in 4 weeks and significant improvement in hemiplegia in a 9-year-old boy with a right anterior cerebral artery and middle cerebral artery infarction, despite Wallerian degeneration apparent on diffusion-weighted imaging. Serial assessment of neglect documenting the rapid course of recovery is the unique feature of this case and may help serve as a guide to pediatricians and neurologists in assessment of young patients and counseling of parents. The lack of published outcome data suggests a need for larger studies about the recovery of spatial neglect and other cognitive symptoms following pediatric stroke.

Hitting a moving target: Basic mechanisms of recovery from acquired developmental brain injury

Acquired brain injuries represent a major cause of disability in the pediatric population. Understanding responses to developmental acquired brain injuries requires knowledge of the neurobiology of normal development, age-at-injury effects and experience-dependent neuroplasticity. In the developing brain, full recovery cannot be considered as a return to the premorbid baseline, since ongoing maturation means that cerebral functioning in normal individuals will continue to advance. Thus, the recovering immature brain has to 'hit a moving target' to achieve full functional recovery, defined as parity with age-matched uninjured peers. This review will discuss the consequences of developmental injuries such as focal lesions, diffuse hypoxia and traumatic brain injury (TBI). Underlying cellular and physiological mechanisms relevant to age-at-injury effects will be described in considerable detail, including but not limited to alterations in neurotransmission, connectivity/network functioning, the extracellular matrix, response to oxidative stress and changes in cerebral metabolism. Finally, mechanisms of experience-dependent plasticity will be reviewed in conjunction with their effects on neural repair and recovery.