Transient aphasias after left hemisphere resective surgery

How well can simple clinical features predict long-term language recovery after left-hemisphere glioma surgery?

PURPOSE

Long-term language recovery after left-hemisphere glioma surgery varies substantially across patients. We investigated how well it can be predicted using clinical variables such as the postoperative decline in language processing, tumor grade, resection volume and location, extent of resection, and intraoperative language mapping. Beyond predicting the overall recovery, we examined which domains of language processing are most prone to persistent deficits.

METHODS

Fifty-nine patients with left-hemisphere gliomas completed the Russian Aphasia Test (RAT) before surgery, immediately after surgery, and at follow-up three to seventeen months after surgery. We modeled their average language score (Generalized Aphasia Quotient, GAQ) at follow-up using a cross-validated multiple linear regression and calculated the number of patients showing persistent deficits in each subtest of the RAT.

RESULTS

The difference between GAQ scores at follow-up and before surgery was not significant at the group level but varied substantially across patients (mean -1.3%, range -34.2 - 9.2%). Our best-performing model predicted the follow-up GAQ scores with the mean absolute error of 3.5% (cross-validated R2 = 0.15). A greater decline in language processing immediately after surgery predicted worse recovery, whereas intraoperative language mapping predicted better recovery. Deficits in sentence repetition, verb production, verb and sentence comprehension, and object naming most often persisted at follow-up.

CONCLUSION

The postoperative decline in language processing and intraoperative language mapping explain a substantial amount of variability in long-term language recovery. Verbal working memory and lexical retrieval, particularly that of verbs, are most prone to persistent deficits.

Demystifying visual word form area visual and nonvisual response properties with precision fMRI

The visual word form area (VWFA) is a region in the left ventrotemporal cortex (VTC) whose specificity remains contentious. Using precision fMRI, we examine the VWFA's responses to numerous visual and nonvisual stimuli, comparing them to adjacent category-selective visual regions and regions involved in language and attentional demand. We find that VWFA responds moderately to non-word visual stimuli, but is unique within VTC in its pronounced selectivity for visual words. Interestingly, the VWFA is also the only category-selective visual region engaged in auditory language, unlike the ubiquitous attentional demand effect throughout the VTC. However, this language selectivity is dwarfed by its visual responses even to nonpreferred categories, indicating the VWFA is not a core (amodal) language region. We also observed two additional auditory language VTC clusters, but these had no specificity for visual words. Our detailed investigation clarifies longstanding controversies about the landscape of visual and auditory language functionality within VTC.

Function-guided differences of arcuate fascicle and inferior fronto-occipital fascicle tractography as diagnostic indicators for surgical risk stratification

BACKGROUND

Several patients with language-eloquent gliomas face language deterioration postoperatively. Persistent aphasia is frequently associated with damage to subcortical language pathways. Underlying mechanisms still need to be better understood, complicating preoperative risk assessment. This study compared qualitative and quantitative functionally relevant subcortical differences pre- and directly postoperatively in glioma patients with and without aphasia.

METHODS

Language-relevant cortical sites were defined using navigated transcranial magnetic stimulation (nTMS) language mapping in 74 patients between 07/2016 and 07/2019. Post-hoc nTMS-based diffusion tensor imaging tractography was used to compare a tract's pre- and postoperative visualization, volume and fractional anisotropy (FA), and the preoperative distance between tract and lesion and postoperative overlap with the resection cavity between the following groups: no aphasia (NoA), tumor- or previous resection induced aphasia persistent pre- and postoperatively (TIA_P), and surgery-induced transient or permanent aphasia (SIA_T or SIA_P).

RESULTS

Patients with NoA, TIA_P, SIA_T, and SIA_P showed distinct fasciculus arcuatus (AF) and inferior-fronto-occipital fasciculus (IFOF) properties. The AF was more frequently reconstructable, and the FA of IFOF was higher in NoA than TIA_P cases (all p ≤ 0.03). Simultaneously, SIA_T cases showed higher IFOF fractional anisotropy than TIA_P cases (p < 0.001) and the most considerable AF volume loss overall. While not statistically significant, the four SIA_P cases showed complete loss of ventral language streams postoperatively, the highest resection-cavity-AF-overlap, and the shortest AF to tumor distance.

CONCLUSION

Functionally relevant qualitative and quantitative differences in AF and IFOF provide a pre- and postoperative pathophysiological and clinically relevant diagnostic indicator that supports surgical risk stratification.

The language network as a natural kind within the broader landscape of the human brain

Language behaviour is complex, but neuroscientific evidence disentangles it into distinct components supported by dedicated brain areas or networks. In this Review, we describe the 'core' language network, which includes left-hemisphere frontal and temporal areas, and show that it is strongly interconnected, independent of input and output modalities, causally important for language and language-selective. We discuss evidence that this language network plausibly stores language knowledge and supports core linguistic computations related to accessing words and constructions from memory and combining them to interpret (decode) or generate (encode) linguistic messages. We emphasize that the language network works closely with, but is distinct from, both lower-level - perceptual and motor - mechanisms and higher-level systems of knowledge and reasoning. The perceptual and motor mechanisms process linguistic signals, but, in contrast to the language network, are sensitive only to these signals' surface properties, not their meanings; the systems of knowledge and reasoning (such as the system that supports social reasoning) are sometimes engaged during language use but are not language-selective. This Review lays a foundation both for in-depth investigations of these different components of the language processing pipeline and for probing inter-component interactions.

Intraoperative language mapping guided by real-time visualization of gamma band modulation electrocorticograms: Case report and proof of concept

Background

Electrocorticography (ECoG) language mapping is often performed extraoperatively, frequently involves offline processing, and relationships with direct cortical stimulation (DCS) remain variable. We sought to determine the feasibility and preliminary utility of an intraoperative language mapping approach guided by real-time visualization of electrocorticograms.

Methods

A patient with astrocytoma underwent awake craniotomy with intraoperative language mapping, utilizing a dual iPad stimulus presentation system coupled to a real-time neural signal processing platform capable of both ECoG recording and delivery of DCS. Gamma band modulations in response to 4 language tasks at each electrode were visualized in real-time. Next, DCS was conducted for each neighboring electrode pair during language tasks.

Results

All language tasks resulted in strongest heat map activation at an electrode pair in the anterior to mid superior temporal gyrus. Consistent speech arrest during DCS was observed for Object and Action naming tasks at these same electrodes, indicating good correspondence with ECoG heat map recordings. This region corresponded well with posterior language representation via preoperative functional MRI.

Conclusions

Intraoperative real-time visualization of language task-based ECoG gamma band modulation is feasible and may help identify targets for DCS. If validated, this may improve the efficiency and accuracy of intraoperative language mapping.

Interindividual variability and consistency of language mapping paradigms for presurgical use

Most functional MRI studies of language processing have focussed on group-level inference, but for clinical use, the aim is to predict outcomes at an individual patient level. This requires being able to identify atypical activation and understand how differences relate to language outcomes. A language mapping paradigm that selectively activates left hemisphere language regions in healthy individuals allows atypical activation in a patient to be more easily identified. We investigated the interindividual variability and consistency of language activation in 12 healthy participants using three tasks-verb generation, responsive naming, and sentence comprehension-for future presurgical use. Responsive naming produced the most consistent left-lateralised activation across participants in frontal and temporal regions that postsurgical voxel-based lesion-symptom mapping studies suggest are most critical for language outcomes. Studies with a long-term clinical aim of predicting language outcomes in neurosurgical patients and stroke patients should first establish paradigm validity at an individual level in healthy participants.

The central role of the left inferior longitudinal fasciculus in the face-name retrieval network

Unsuccessful retrieval of proper names (PNs) is commonly observed in patients suffering from neurological conditions such as stroke or epilepsy. While a large body of works has suggested that PN retrieval relies on a cortical network centered on the left anterior temporal lobe (ATL), much less is known about the white matter connections underpinning this process. Sparse studies provided evidence for a possible role of the uncinate fasciculus, but the inferior longitudinal fasciculus (ILF) might also contribute, since it mainly projects into the ATL, interconnects it with the posterior lexical interface and is engaged in common name (CN) retrieval. To ascertain this hypothesis, we assessed 58 patients having undergone a neurosurgery for a left low-grade glioma by means of a famous face naming (FFN) task. The behavioural data were processed following a multilevel lesion approach, including location-based analyses, voxel-based lesion-symptom mapping (VLSM) and disconnection-symptom mapping. Different statistical models were generated to control for sociodemographic data, familiarity, biographical knowledge and control cognitive performances (i.e., semantic and episodic memory and CN retrieval). Overall, VLSM analyses indicated that damage to the mid-to-anterior part of the ventro-basal temporal cortex was especially associated with PN retrieval deficits. As expected, tract-oriented analyses showed that the left ILF was the most strongly associated pathway. Our results provide evidence for the pivotal role of the ILF in the PN retrieval network. This novel finding paves the way for a better understanding of the pathophysiological bases underlying PN retrieval difficulties in the various neurological conditions marked by white matter abnormalities.

Chronic aphasias after left-hemisphere resective surgery

Surgical resection of brain tumours is associated with an increased risk of aphasia. However, relatively little is known about outcomes in the chronic phase (i.e., >6 months). Using voxel-based lesion symptom mapping (VLSM) in 46 patients, we investigated whether chronic language impairments are related to the location of surgical resection, residual tumour characteristics (e.g., peri-resection treatment effects, progressive infiltration, oedema) or both. Approximately 72% of patients scored below the cut-off for aphasia. Action naming and spoken sentence comprehension deficits were associated with lesions in the left anterior temporal and inferior parietal lobes, respectively. Voxel-wise analyses revealed significant associations between ventral language pathways and action naming deficits. Reading impairments were also associated with increasing disconnection of cerebellar pathways. The results indicate chronic post-surgical aphasias reflect a combination of resected tissue and tumour infiltration of language-related white matter tracts, implicating progressive disconnection as the critical mechanism of impairment.

Dissociation of Broca's area from Broca's aphasia in patients undergoing neurosurgical resections

OBJECTIVE

Broca's aphasia is a syndrome of impaired fluency with retained comprehension. The authors used an unbiased algorithm to examine which neuroanatomical areas are most likely to result in Broca's aphasia following surgical lesions.

METHODS

Patients were prospectively evaluated with standardized language batteries before and after surgery. Broca's area was defined anatomically as the pars opercularis and triangularis of the inferior frontal gyrus. Broca's aphasia was defined by the Western Aphasia Battery language assessment. Resections were outlined from MRI scans to construct 3D volumes of interest. These were aligned using a nonlinear transformation to Montreal Neurological Institute brain space. A voxel-based lesion-symptom mapping (VLSM) algorithm was used to test for areas statistically associated with Broca's aphasia when incorporated into a resection, as well as areas associated with deficits in fluency independent of Western Aphasia Battery classification. Postoperative MRI scans were reviewed in blinded fashion to estimate the percentage resection of Broca's area compared to areas identified using the VLSM algorithm.

RESULTS

A total of 289 patients had early language evaluations, of whom 19 had postoperative Broca's aphasia. VLSM analysis revealed an area that was highly correlated (p < 0.001) with Broca's aphasia, spanning ventral sensorimotor cortex and supramarginal gyri, as well as extending into subcortical white matter tracts. Reduced fluency scores were significantly associated with an overlapping region of interest. The fluency score was negatively correlated with fraction of resected precentral, postcentral, and supramarginal components of the VLSM area.

CONCLUSIONS

Broca's aphasia does not typically arise from neurosurgical resections in Broca's area. When Broca's aphasia does occur after surgery, it is typically in the early postoperative period, improves by 1 month, and is associated with resections of ventral sensorimotor cortex and supramarginal gyri.

Critical role of the ventral temporal lobe in naming

OBJECTIVE

Lexical retrieval deficits are characteristic of a variety of different neurological disorders. However, the exact substrates responsible for this are not known. We studied a large cohort of patients undergoing surgery in the dominant temporal lobe for medically intractable epilepsy (n = 95) to localize brain regions that were associated with anomia.

METHODS

We performed a multivariate voxel-based lesion-symptom mapping analysis to correlate surgical lesions within the temporal lobe with changes in naming ability. Additionally, we used a surface-based mixed-effects multilevel analysis to estimate group-level broadband gamma activity during naming across a subset of patients with electrocorticographic recordings and integrated these results with lesion-deficit findings.

RESULTS

We observed that ventral temporal regions, centered around the middle fusiform gyrus, were significantly associated with a decline in naming. Furthermore, we found that the ventral aspect of temporal lobectomies was linearly correlated to a decline in naming, with a clinically significant decline occurring once the resection extended 6 cm from the anterior tip of the temporal lobe on the ventral surface. On electrocorticography, the majority of these cortical regions were functionally active following visual processing. These loci coincide with the sites of susceptibility artifacts during echoplanar imaging, which may explain why this region has been previously underappreciated as the locus responsible for postoperative naming deficits.

SIGNIFICANCE

Taken together, these data highlight the crucial contribution of the ventral temporal cortex in naming and its important role in the pathophysiology of anomia following temporal lobe resections. As such, surgical strategies should attempt to preserve this region to mitigate postoperative language deficits.

A Neurosurgical Functional Dissection of the Middle Precentral Gyrus during Speech Production

Classical models have traditionally focused on the left posterior inferior frontal gyrus (Broca's area) as a key region for motor planning of speech production. However, converging evidence suggests that it is not critical for either speech motor planning or execution. Alternative cortical areas supporting high-level speech motor planning have yet to be defined. In this review, we focus on the precentral gyrus, whose role in speech production is often thought to be limited to lower-level articulatory muscle control. In particular, we highlight neurosurgical investigations that have shed light on a cortical region anatomically located near the midpoint of the precentral gyrus, hence called the middle precentral gyrus (midPrCG). The midPrCG is functionally located between dorsal hand and ventral orofacial cortical representations and exhibits unique sensorimotor and multisensory functions relevant for speech processing. This includes motor control of the larynx, auditory processing, as well as a role in reading and writing. Furthermore, direct electrical stimulation of midPrCG can evoke complex movements, such as vocalization, and selective injury can cause deficits in verbal fluency, such as pure apraxia of speech. Based on these findings, we propose that midPrCG is essential to phonological-motoric aspects of speech production, especially syllabic-level speech sequencing, a role traditionally ascribed to Broca's area. The midPrCG is a cortical brain area that should be included in contemporary models of speech production with a unique role in speech motor planning and execution.

Presurgical predictors of early cognitive outcome after brain tumor resection in glioma patients

Gliomas are commonly characterized by neurocognitive deficits that strongly impact patients' and caregivers' quality of life. Surgical resection is the mainstay of therapy, and it can also cause cognitive impairment. An important clinical problem is whether patients who undergo surgery will show post-surgical cognitive impairment above and beyond that present before surgery. The relevant rognostic factors are largely unknown. This study aims to quantify the cognitive impairment in glioma patients 1-week after surgery and to compare different pre-surgical information (i.e., cognitive performance, tumor volume, grading, and lesion topography) towards predicting early post-surgical cognitive outcome. We retrospectively recruited a sample of N = 47 patients affected by high-grade and low-grade glioma undergoing brain surgery for tumor resection. Cognitive performance was assessed before and immediately after (∼1 week) surgery with an extensive neurocognitive battery. Multivariate linear regression models highlighted the combination of predictors that best explained post-surgical cognitive impairment. The impact of surgery on cognitive functioning was relatively small (i.e., 85% of test scores across the whole sample indicated no decline), and pre-operative cognitive performance was the main predictor of early post-surgical cognitive outcome above and beyond information from tumor topography and volume. In fact, structural lesion information did not significantly improve the accuracy of prediction made from cognitive data before surgery. Our findings suggest that post-surgery neurocognitive deficits are only partially explained by preoperative brain damage. The present results suggest the possibility to make reliable, individualized, and clinically relevant predictions from relatively easy-to-obtain information.

Neuromonitoring of the language pathways using cortico-cortical evoked potentials: a systematic review and meta-analysis

Cortico-cortical evoked potentials (CCEPs) are a surge in activity of one cortical zone caused by stimulation of another cortical zone. Recording of CCEP may be a useful method of intraoperative monitoring of the brain pathways, particularly of the language-related tracts. We aimed to conduct a systematic review and meta-analysis, dedicated to the clinical question: Does the CCEP recording effectively predict the postoperative speech deficits in neurosurgical patients? We conducted language-restricted PubMed, Google Scholar, Scopus, and Cochrane database search for eligible studies of CCEP published until March 2021. There were 4 articles (3 case series and 1 case report), which met our inclusion/exclusion criteria. A total of 32 patients (30 cases of tumors and 2 cavernomas) included in the analysis were divided into two cohorts - quantitative and qualitative, in accordance with the method of evaluating changes in the amplitude of CCEP after the lesion resection and postoperative alterations in speech function. Quantitative variables were studied using the Spearman rank correlation coefficient. Categorical variables were compared in groups by Fisher's exact test. We found a strong positive correlation between the decrease in the N1 wave amplitude and the severity of postoperative speech deficits (quantitative cohort: r = 0.57, p = 0.01; qualitative cohort: p = 0.02). Thus, the CCEP method using the N1 wave amplitude as a marker enables to effectively predict postoperative speech outcomes. Nevertheless, the low level of evidence for the included works indicated the necessity for additional research on this issue.

'Moderate global aphasia': A generalized decline of language processing caused by glioma surgery but not stroke

Unlike stroke, neurosurgical removal of left-hemisphere gliomas acts upon a reorganized language network and involves brain areas rarely damaged by stroke. We addressed whether this causes the profiles of neurosurgery- and stroke-induced language impairments to be distinct. K-means clustering of language assessment data (neurosurgery cohort: N = 88, stroke cohort: N = 95) identified similar profiles in both cohorts. But critically, a cluster of individuals with specific phonological deficits was only evident in the stroke but not in the neurosurgery cohort. Thus, phonological deficits are less clearly distinguished from other language deficits after glioma surgery compared to stroke. Furthermore, the correlations between language production and comprehension scores at different linguistic levels were more extensive in the neurosurgery than in the stroke cohort. Our findings suggest that neurosurgery-induced language impairments do not correspond to those caused by stroke, but rather manifest as a 'moderate global aphasia' - a generalized decline of language processing abilities.

Resection of dominant fusiform gyrus is associated with decline of naming function when temporal lobe epilepsy manifests after the age of five: A voxel-based lesion-symptom mapping study

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Resection in the dominant fusiform gyrus is associated with an increased risk of postoperative decline in picture naming.

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More temporo-posterior resections in this area results in a greater degree of naming decline.

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Risk of significant naming decline after left temporal surgery increased by 5% with every year of later seizure onset.

Objective

To determine patients’ characteristics and regions in the temporal lobe where resections lead to a decline in picture naming.

Methods

311 patients with left hemispheric dominance for language were included who underwent epilepsy surgery at the Epilepsy Center of Erlangen and whose picture naming scores (Boston Naming Test, BNT) were available preoperatively and 6-months postoperatively. Surgical lesions were mapped to an averaged template based on preoperative and postoperative MRI using voxel-based lesion-symptom mapping (VBLSM). Postoperative brain shifts were corrected. The relationship between lesioned brain areas and the presence of a postoperative naming decline was examined voxel-wise while controlling for effects of overall lesion size at first in the total cohort and then restricted to temporal lobe resections.

Results

In VBLSM in the total sample, a decline in BNT score was significantly related to left temporal surgery. When only considering patients with left temporal lobe resections (n = 121), 40 (33.1%) significantly worsened in BNT postoperatively. VBLSM including all patients with left temporal resections generated no significant results within the temporal lobe. However, naming decline of patients with epilepsy onset after 5 years of age was significantly associated with resections in the left inferior temporal (extent of BNT decline range: 10.8− 14.4%) and fusiform gyrus (decline range: 12.1−18.4%).

Significance

Resections in the posterior part of the dominant fusiform and inferior temporal gyrus was associated with a risk of deterioration in naming performance at six months after surgery in patients with epilepsy onset after 5 years of age but not with earlier epilepsy onset.

Impairment and Plasticity of Language-Related White Matter in Patients With Brain Arteriovenous Malformations

BACKGROUND AND PURPOSE

Language dysfunction is rarely seen in patients with unruptured brain arteriovenous malformation (AVM) albeit the AVM nidus involving language areas, which provides a unique disease model to study language reorganization. The objective of this study was to investigate the impairment and reorganization patterns and characteristics of language-related white matter in AVMs located at different brain areas.

METHODS

Thirty-three patients with AVMs involving language areas were prospectively enrolled. Patients were categorized into 3 groups according to the lesion locations: the frontal (14 patients), temporal (15 patients), and parietal groups (4 patients). Thirty age- and sex-matched healthy controls were enrolled as comparison. All participants underwent diffusion tensor imaging scans, and automated fiber quantification method was applied to quantitatively study the difference of segmented language-related white matter connectivity between 3 AVM groups and control group.

RESULTS

Language functions were normal in all subjects according to Western Aphasia Battery test. In the frontal group, fractional anisotropy (FA) value decreased in the left arcuate fascicle and increased in left superior longitudinal fasciculus and uncinate fascicle; in the temporal group, FA values decreased in left inferior fronto-occipital fascicle and inferior longitudinal fascicle and increased in right anterior thalamic radiation and uncinate fascicle; in the parietal group, FA values decreased in left arcuate fascicle and inferior longitudinal fascicle and increased in bilateral anterior thalamic radiations and uncinate fascicles and right inferior fronto-occipital fascicle. In fascicles with decreased FA values, the increase of radial diffusivity was common, and fascicles with increased FA values usually presented along with increased axial diffusivity values.

CONCLUSIONS

Remodeling of language-related white matter occurs when traditional language areas are involved by AVM nidus, and its reorganization patterns vary with locations of AVM nidus. Fascicle impairment is mainly caused by the myelin deficits, and its plasticity may be dominated by the axon remodeling procedure.

Aphasic status epilepticus after glioma resection: two case reports

Aphasic status epilepticus (ASE) is a subtype of focal nonconvulsive status epilepticus, in which language disturbance is the only objective clinical manifestation. We present two cases of patients who experienced delayed onset of temporal aphasia after the removal of glioma at the language-dominant hemisphere. In both cases, arterial spin labeling was useful for diagnosis and antiepileptic drug was effective. ASE should be considered a cause of persistent aphasia after glioma resection at or near the language area.

Language reorganization after resection of low-grade gliomas: an fMRI task based connectivity study

Few studies addressed the evolution of brain activity before and after brain tumor resection. Using a fMRI naming task, we evaluated possible underlying plasticity phenomena. Thirty-two patients with left low-grade gliomas (16 women; age = 38.6 ± 8.31 years) and 19 healthy controls (7 women; age = 42.4 ± 12.1) were included in the study. An overt picture-naming task (DO80) was performed pre and post (3 months) surgery, as well as within the MRI in a covert manner. Exams included an injected 3DT1, a T2FLAIR, a DTI and a GE-EPI (task) sequence. Activations maps were compared with picture naming score, FA and MD maps were estimated, a VLSM analysis was performed on tumor masks, and disconnectome maps were reconstructed. Pre-surgery, the left parahippocampal gyrus (LPH) was inversely associated with task performance. Increased pre-post surgery left lingual gyrus (LLG) activity was found related to decreased picture naming performance. The evolution of left lingual gyrus (LLG) activity was negatively associated with the evolution of picture naming performance. In controls, the LPH was functionally connected to the right precentral gyrus (RPCG) and slightly to the LLG. This was not clearly retrieved in the patient group. Preoperatively, the LLG was connected to the left planum temporale and to the right lingual gyrus. The same result was found for controls. Postoperatively, the LLG was only connected to the RPCG. No association was found between evolution of FA/MD and evolution of picture naming performance. There is not one unique pattern of pre- and postoperative plasticity concerning picture-naming performance in DLGG patients.

The impact of high functional connectivity network hub resection on language task performance in adult low- and high-grade glioma

OBJECTIVE

Gliomas are intrinsic brain tumors with the hallmark of diffuse white matter infiltration, resulting in short- and long-range network dysfunction. Preoperative magnetoencephalography (MEG) can assist in maximizing the extent of resection while minimizing morbidity. While MEG has been validated in motor mapping, its role in speech mapping remains less well studied. The authors assessed how the resection of intraoperative electrical stimulation (IES)-negative, high functional connectivity (HFC) network sites, as identified by MEG, impacts language performance.

METHODS

Resting-state, whole-brain MEG recordings were obtained from 26 patients who underwent perioperative language evaluation and glioma resection that was guided by awake language and IES mapping. The functional connectivity of an individual voxel was determined by the imaginary coherence between the index voxel and the rest of the brain, referenced to its contralesional pair. The percentage of resected HFC voxels was correlated with postoperative language outcomes in tasks of increasing complexity: text reading, 4-syllable repetition, picture naming, syntax (SYN), and auditory stimulus naming (AN).

RESULTS

Overall, 70% of patients (14/20) in whom any HFC tissue was resected developed an early postoperative language deficit (mean 2.3 days, range 1-8 days), compared to 33% of patients (2/6) in whom no HFC tissue was resected (p = 0.16). When bifurcated by the amount of HFC tissue that was resected, 100% of patients (3/3) with an HFC resection > 25% displayed deficits in AN, compared to 30% of patients (6/20) with an HFC resection < 25% (p = 0.04). Furthermore, there was a linear correlation between the severity of AN and SYN decline with percentage of HFC sites resected (p = 0.02 and p = 0.04, respectively). By 2.2 months postoperatively (range 1-6 months), the correlation between HFC resection and both AN and SYN decline had resolved (p = 0.94 and p = 1.00, respectively) in all patients (9/9) except two who experienced early postoperative tumor progression or stroke involving inferior frontooccipital fasciculus.

CONCLUSIONS

Imaginary coherence measures of functional connectivity using MEG are able to identify HFC network sites within and around low- and high-grade gliomas. Removal of IES-negative HFC sites results in early transient postoperative decline in AN and SYN, which resolved by 3 months in all patients without stroke or early tumor progression. Measures of functional connectivity may therefore be a useful means of counseling patients about postoperative risk and assist with preoperative surgical planning.

Central Nervous System Plasticity Influences Language and Cognitive Recovery in Adult Glioma

Gliomas exist within the framework of complex neuronal circuitry in which network dynamics influence both tumor biology and cognition. The generalized impairment of cognition or loss of language function is a common occurrence for glioma patients. The interface between intrinsic brain tumors such as gliomas and functional cognitive networks are poorly understood. The ability to communicate effectively is critically important for receiving oncological therapies and maintaining a high quality of life. Although the propensity of gliomas to infiltrate cortical and subcortical structures and disrupt key anatomic language pathways is well documented, there is new evidence offering insight into the network and cellular mechanisms underpinning glioma-related aphasia and aphasia recovery. In this review, we will outline the current understanding of the mechanisms of cognitive dysfunction and recovery, using aphasia as an illustrative model.

Data-Driven, Visual Framework for the Characterization of Aphasias Across Stroke, Post-resective, and Neurodegenerative Disorders Over Time

Aphasia classifications and specialized language batteries differ across the fields of neurodegenerative disorders and lesional brain injuries, resulting in difficult comparisons of language deficits across etiologies. In this study, we present a simplified framework, in which a widely-used aphasia battery captures clinical clusters across disease etiologies and provides a quantitative and visual method to characterize and track patients over time. The framework is used to evaluate populations representing three disease etiologies: stroke, primary progressive aphasia (PPA), and post-operative aphasia. A total of 330 patients across three populations with cerebral injury leading to aphasia were investigated, including 76 patients with stroke, 107 patients meeting criteria for PPA, and 147 patients following left hemispheric resective surgery. Western Aphasia Battery (WAB) measures (Information Content, Fluency, answering Yes/No questions, Auditory Word Recognition, Sequential Commands, and Repetition) were collected across the three populations and analyzed to develop a multi-dimensional aphasia model using dimensionality reduction techniques. Two orthogonal dimensions were found to explain 87% of the variance across aphasia phenotypes and three disease etiologies. The first dimension reflects shared weighting across aphasia subscores and correlated with aphasia severity. The second dimension incorporates fluency and comprehension, thereby separating Wernicke's from Broca's aphasia, and the non-fluent/agrammatic from semantic PPA variants. Clusters representing clinical classifications, including late PPA presentations, were preserved within the two-dimensional space. Early PPA presentations were not classifiable, as specialized batteries are needed for phenotyping. Longitudinal data was further used to visualize the trajectory of aphasias during recovery or disease progression, including the rapid recovery of post-operative aphasic patients. This method has implications for the conceptualization of aphasia as a spectrum disorder across different disease etiology and may serve as a framework to track the trajectories of aphasia progression and recovery.

Clinical Pearls and Methods for Intraoperative Awake Language Mapping

Intraoperative language mapping of tumor and peritumor tissue is a well-established technique for avoiding permanent neurological deficits and maximizing extent of resection. Although there are several components of language that may be tested intraoperatively (eg, naming, writing, reading, and repetition), there is a lack of consistency in how patients are tested intraoperatively as well as the techniques involved to ensure safety during an awake procedure. Here, we review appropriate patient selection, neuroanesthetic techniques, cortical and subcortical language mapping stimulation paradigms, and selection of intraoperative language tasks used during awake craniotomies. We also expand on existing language mapping reviews by considering how intensity and timing of electrical stimulation may impact interpretation of mapping results.

Baseline neuropsychological characteristics in patients with epilepsy with left temporal lobe encephaloceles compared with left mesial temporal sclerosis

BACKGROUND

Temporal lobe encephaloceles (TE) are increasingly recognized as a cause of drug-resistant temporal lobe epilepsy. Improved recognition of these lesions offers an opportunity to treat them with a limited resection sparing the hippocampus. However, as they can be difficult to identify on imaging, additional clues pointing to the diagnosis can be helpful. We sought to understand the baseline cognitive/neuropsychological profile in patients with left temporal lobe epilepsy caused by encephaloceles compared with that caused by mesial temporal sclerosis (MTS), a common entity in the differential diagnosis.

METHODS

Neuropsychological testing, including language (semantic and phonemic fluency and naming), verbal memory, intelligence quotient (IQ), and executive function measures were compared across two groups (five patients with left TE and five age- and gender-matched patients with left MTS). Other clinical variables related to cognition, including patient age, electroencephalographic characteristics, epilepsy duration, and factors related to antiseizure medication dosing, were also compared between groups.

RESULTS

More patients with left MTS had atypical language lateralization (3/5 with right-sided language in the group with MTS compared with 0/5 in the group with TE). Patients with MTS had significantly worse scores on the Verbal Comprehension Index (VCI) subscore of the Wechsler Adult Intelligence Scale (WAIS; p = 0.026). General IQ was also worse in patients with MTS (p = 0.028). There was a trend towards worse executive function in patients with MTS as measured on Trails B (p = 0.096). Other measures related to language and verbal memory did not differ significantly between the groups nor did other relevant clinical variables, except epilepsy duration, which was significantly longer in patients with MTS (p = 0.0001).

CONCLUSIONS

This pilot study demonstrates few significant differences between the groups with left MTS and TE surveyed. A higher rate of atypical language lateralization was noted in patients with left MTS. The higher baseline global IQ and VCI scores in patients with left TE compared with patients with MTS may be attributable to longer duration of epilepsy in patients with left MTS. Future work with a larger sample size will focus on establishing a unique neuropsychological profile related to epilepsy due to TE.

Across-session consistency of context-driven language processing: A magnetoencephalography study

Changes in brain organization following damage are commonly observed, but they remain poorly understood. These changes are often studied with imaging techniques that overlook the temporal granularity at which language processes occur. By contrast, electrophysiological measures provide excellent temporal resolution. To test the suitability of magnetoencephalography (MEG) to track language‐related neuroplasticity, the present study aimed at establishing the spectro‐temporo‐spatial across‐session consistency of context‐driven picture naming in healthy individuals, using MEG in two test–retest sessions. Spectro‐temporo‐spatial test–retest consistency in a healthy population is a prerequisite for studying neuronal changes in clinical populations over time. For this purpose, 15 healthy speakers were tested with MEG while performing a context‐driven picture‐naming task at two time points. Participants read a sentence missing the final word and named a picture completing the sentence. Sentences were constrained or unconstrained toward the picture, such that participants could either retrieve the picture name through sentence context (constrained sentences), or could only name it after the picture appeared (unconstrained sentences). The context effect (constrained versus unconstrained) in picture‐naming times had a strong effect size and high across‐session consistency. The context MEG results revealed alpha–beta power decreases (10–20 Hz) in the left temporal and inferior parietal lobule that were consistent across both sessions. As robust spectro‐temporo‐spatial findings in a healthy population are required for working toward longitudinal patient studies, we conclude that using context‐driven language production and MEG is a suitable way to examine language‐related neuroplasticity after brain damage.

Risk Assessment by Presurgical Tractography Using Navigated TMS Maps in Patients with Highly Motor- or Language-Eloquent Brain Tumors

Patients with functionally eloquent brain lesions are at risk of functional decline in the course of resection. Given tumor-related plastic reshaping and reallocation of function, individual data are needed for patient counseling and risk assessment prior to surgery. This study evaluates the utility of mapping by navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging fiber tracking (DTI FT) for individual risk evaluation of surgery-related decline of motor or language function in the clinical setting. In total, 250 preoperative nTMS mappings (100 language and 150 motor mappings) derived from 216 patients (mean age: 57.0 ± 15.5 years, 58.8% males; glioma World Health Organization (WHO) grade I & II: 4.2%, glioma WHO grade III & IV: 83.4%, arteriovenous malformations: 1.9%, cavernoma: 2.3%, metastasis: 8.2%) were included. Deterministic tractography based on nTMS motor or language maps as seed regions was performed with 25%, 50%, and 75% of the individual fractional anisotropy threshold (FAT). Lesion-to-tract distances (LTDs) were measured between the tumor mass and the corticospinal tract (CST), arcuate fascicle (AF), or other closest language-related tracts. LTDs were compared between patients and correlated to the functional status (no/transient/permanent surgery-related paresis or aphasia). Significant differences were found between patients with no or transient surgery-related deficits and patients with permanent surgery-related deficits regarding LTDs in relation to the CST (p < 0.0001), AF (p ≤ 0.0491), or other closest language-related tracts (p ≤ 0.0435). The cut-off values for surgery-related paresis or aphasia were ≤12 mm (LTD—CST) and ≤16 mm (LTD—AF) or ≤25 mm (LTD—other closest language-related tract), respectively. Moreover, there were significant associations between the status of surgery-related deficits and the LTD when considering the CST (range r: −0.3994 to −0.3910, p < 0.0001) or AF (range r: −0.2918 to −0.2592, p = 0.0135 and p = 0.0473 for 25% and 50% FAT). In conclusion, this is the largest study evaluating the application of both preoperative functional mapping and function-based tractography for motor and language function for risk stratification in patients with functionally eloquent tumors. The LTD may qualify as a viable marker that can be seamlessly assessed in the clinical neurooncological setup.

Post-stroke cognitive deficits rarely come alone: Handling co-morbidity in lesion-behaviour mapping

Post‐stroke behavioural symptoms often correlate and systematically co‐occur with each other, either because they share cognitive processes, or because their neural correlates are often damaged together. Thus, neuropsychological symptoms often share variance. Many previous lesion‐behaviour mapping studies aimed to methodologically consider this shared variance between neuropsychological variables. A first group of studies controlled the behavioural target variable for the variance explained by one or multiple other variables to obtain a more precise mapping of the target variable. A second group of studies focused on the shared variance of multiple variables itself with the aim to map neural correlates of cognitive processes that are shared between the original variables. In the present study, we tested the validity of these methods by using real lesion data and both real and simulated data sets. We show that the variance that is shared between post‐stroke behavioural variables is ambiguous, and that mapping procedures that consider this variance are prone to biases and artefacts. We discuss under which conditions such procedures could still be used and what alternative approaches exist.

Reorganized language network connectivity after left arcuate fasciculus resection: A case study

Understanding the neural mechanisms that support spontaneous recovery of cognitive abilities can place important constraints on mechanistic theories of brain organization and function, and holds potential to inform clinical interventions. Connectivity-based MRI measures have emerged as a way to study how recovery from brain injury is modulated by changes in intra- and inter-hemispheric connectivity. Here we report a detailed and multi-modal case study of a 26 year-old male who presented with a left inferior parietal glioma infiltrating the left arcuate fasciculus. The patient underwent pre- and post-operative functional MRI and Diffusion Tensor Imaging, as well as behavioral assessments of language, motor, vision and praxis. The surgery for removal of the tumor was carried out with the patient awake, and direct electrical stimulation mapping was used to evaluate cortical language centers. The patient developed a specific difficulty with repeating sentences toward the end of the surgery, after resection of the tumor and partial transection of the arcuate fasciculus. The patient recovered from the sentence repetition impairments over several months after the operation. Coincident with the patient's cognitive recovery, we document a pattern whereby intra-hemispheric functional connectivity was reduced in the left hemisphere, while inter-hemispheric connectivity increased between classic left hemisphere language regions and their right hemisphere homologues. These findings suggest that increased synchrony between the two hemispheres, in the setting of focal transection of the left arcuate fasciculus, can facilitate functional recovery.

Mapping eloquent cortex: A voxel-based lesion-symptom mapping study of core speech production capacities in brain tumour patients

This study used voxel-based lesion-symptom mapping to examine the cortical and white matter regions associated with language production impairments in a sample of 63 preoperative tumour patients. We identified four cognitive functions considered crucial for spoken language production: semantic-to-lexical mapping (selecting the appropriate lexical label for the intended concept); phonological encoding (retrieving the word's phonological form); articulatory-motor planning (programming the articulatory motor movements); and goal-driven language selection (exerting top-down control over the words selected for production). Each participant received a score estimating their competence on each function. We then mapped the region(s) where pathology was significantly associated with low scores. For semantic-to-lexical mapping, the critical map encompassed portions of the left posterior middle and inferior temporal gyri, extending into posterior fusiform gyrus, overlapping substantially with the territory of the inferior longitudinal fasciculus. For phonological encoding, the map encompassed the left inferior parietal lobe and posterior middle temporal gyrus, overlapping with the territory of the inferior longitudinal and posterior arcuate fasciculi. For articulatory-motor planning, the map encompassed parts of the left frontal pole, frontal operculum, and inferior frontal gyrus, and overlapped with the territory of the frontal aslant tract. Finally, the map for goal-driven language selection encompassed the left frontal pole and the anterior cingulate cortex. We compare our findings with those from other neuropsychological samples, and conclude that the study of tumour patients offers evidence that complements that available from other populations.

Impact of AVM location on language cortex right-hemisphere reorganization: A voxel-based lesion-symptom mapping study

OBJECTIVES

Cerebral arteriovenous malformations (AVMs) are congenital malformations, and right-sided dominance of the language cortex is not a rare phenomenon for patients with AVM involving language area. We tried to use voxel-based lesion-symptom mapping (VLSM) method to depict the location of AVM nidus and to demonstrate the relationship between AVM location and the pattern of language cortex reorganization.

PATIENTS AND METHODS

The authors retrospectively reviewed clinical and imaging data of 70 adult patients with unruptured cerebral AVMs who underwent blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) of language task. All patients were right handed, and all lesions were located in the left cerebral hemisphere. Lateralization indexes (LI) of the BOLD signals were calculated for Broca and Wernicke areas separately and were used to reflect the degree of right-sided dominance of the two language areas. VLSM method was applied to study the relationship between AVM location and LI of language task activations.

RESULTS

Statistical analysis revealed that the change of LI of Broca area was significantly associated with lesions located in the inferior frontal gyrus, pre- and post-central gyrus, supramarginal gyrus and middle frontal gyrus. The change of LI of Wernicke area was significantly associated with lesions located in the left superior, middle, inferior and transverse temporal gyrus.

CONCLUSION

These findings provide new evidence that the language cortex reorganization patterns in AVM patients have anatomic specificity.

Resting state network plasticity related to picture naming in low-grade glioma patients before and after resection

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Patients post DLGG surgery use attentional resources to compensate deficit.

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Functional plasticity occurs at secondary regions at distance from the lesion.

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Picture naming requires the integration of multiple resting-state networks.

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The right hemisphere plays also an important role in language processing.

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A whole brain approach with clinical input in case of lesion is the way forward.

The dynamic connectome perspective states that brain functions arise from the functional integration of distributed and/or partly overlapping networks. Diffuse low-grade gliomas (DLGG) have a slow infiltrating character. Here we addressed whether and how anatomical disconnection following DLGG growth and resection might interfere with functional resting-state connectivity, specifically in relation to picture naming.

Thirty-nine native French persons with a left DLGG were included. All underwent awake surgical resection of the tumor using direct brain electrostimulation to preserve critical eloquent regions. The anatomical disconnectivity risk following the DLGG volume and the resection, and the functional connectivity of resting-state fMRI images in relation to picture naming were evaluated prior to and three months after surgery. Resting-state connectivity patterns were compared with nineteen healthy controls.

It was demonstrated that picture naming was strongly dependent on the semantic network that emerged from the integration and interaction of regions within multiple resting-state brain networks, in which their specific role could be explained in the light of the broader resting-state network they take part in. It emphasized the importance of a whole brain approach with specific clinical data input, during resting-state analysis in case of lesion. Adaptive plasticity was found in secondary regions, functionally connected to regions close to the tumor and/or cavity, marked by an increased connectivity of the right and left inferior parietal lobule with the left inferior temporal gyrus. In addition, an important role was identified for the superior parietal lobe, connected with the frontal operculum, suggesting functional compensation by means of attentional resources in order to name a picture via recruitment of the frontoparietal attention network.

Setup presentation and clinical outcome analysis of treating highly language-eloquent gliomas via preoperative navigated transcranial magnetic stimulation and tractography

OBJECTIVE Awake surgery combined with intraoperative direct electrical stimulation (DES) and intraoperative neuromonitoring (IONM) is considered the gold standard for the resection of highly language-eloquent brain tumors. Different modalities, such as functional magnetic resonance imaging (fMRI) or magnetoencephalography (MEG), are commonly added as adjuncts for preoperative language mapping but have been shown to have relevant limitations. Thus, this study presents a novel multimodal setup consisting of preoperative navigated transcranial magnetic stimulation (nTMS) and nTMS-based diffusion tensor imaging fiber tracking (DTI FT) as an adjunct to awake surgery. METHODS Sixty consecutive patients (63.3% men, mean age 47.6 ± 13.3 years) suffering from highly language-eloquent left-hemispheric low- or high-grade glioma underwent preoperative nTMS language mapping and nTMS-based DTI FT, followed by awake surgery for tumor resection. Both nTMS language mapping and DTI FT data were available for resection planning and intraoperative guidance. Clinical outcome parameters, including craniotomy size, extent of resection (EOR), language deficits at different time points, Karnofsky Performance Scale (KPS) score, duration of surgery, and inpatient stay, were assessed. RESULTS According to postoperative evaluation, 28.3% of patients showed tumor residuals, whereas new surgery-related permanent language deficits occurred in 8.3% of patients. KPS scores remained unchanged (median preoperative score 90, median follow-up score 90). CONCLUSIONS This is the first study to present a clinical outcome analysis of this very modern approach, which is increasingly applied in neurooncological centers worldwide. Although human language function is a highly complex and dynamic cortico-subcortical network, the presented approach offers excellent functional and oncological outcomes in patients undergoing surgery of lesions affecting this network.

Naming fMRI predicts the effect of temporal lobe resection on language decline

OBJECTIVE

To develop language functional MRI (fMRI) methods that accurately predict postsurgical naming decline in temporal lobe epilepsy (TLE).

METHODS

Forty-six patients with TLE (25 left) and 19 controls underwent two overt fMRI paradigms (auditory naming and picture naming, both with active baseline conditions) and one covert task (verbal fluency). Clinical naming performance was assessed preoperatively and 4 months following anterior temporal lobe resection. Preoperative fMRI activations were correlated with postoperative naming decline. Individual laterality indices (LI) were calculated for temporal (auditory and picture naming) and frontal regions (verbal fluency) and were considered as predictors of naming decline in multiple regression models, along with other clinical variables (age at onset of seizures, preoperative naming scores, hippocampal volume, age).

RESULTS

In left TLE patients, activation of the left posterior inferior temporal gyrus during auditory naming and activation of left fusiform gyrus during picture naming were related to greater postoperative naming decline. Activation LI were the best individual predictors of naming decline in a multivariate regression model. For picture naming, an LI of higher than 0.34 gave 100% sensitivity and 92% specificity (positive predictive value (PPV) 91.6%). For auditory naming, a temporal lobe LI higher than 0.18 identified all patients with a clinically significant naming decline with 100% sensitivity and 58% specificity (PPV: 58.3%). No effect was seen for verbal fluency.

INTERPRETATION

Auditory and picture naming fMRI are clinically applicable to predict postoperative naming decline after left temporal lobe resection in individual patients, with picture naming being more specific.

Multivariate Approaches to Understanding Aphasia and its Neural Substrates

PURPOSE OF REVIEW

Aphasia is often characterized in terms of subtype and severity, yet these constructs have limited explanatory power, because aphasia is inherently multifactorial both in its neural substrates and in its symptomatology. The purpose of this review is to survey current and emerging multivariate approaches to understanding aphasia.

RECENT FINDINGS

Techniques such as factor analysis and principal component analysis have been used to define latent underlying factors that can account for performance on batteries of speech and language tests, and for characteristics of spontaneous speech production. Multivariate lesion-symptom mapping has been shown to outperform univariate approaches to lesion-symptom mapping for identifying brain regions where damage is associated with specific speech and language deficits. It is increasingly clear that structural damage results in functional changes in wider neural networks, which mediate speech and language outcomes. Multivariate statistical approaches are essential for understanding the complex relationships between the neural substrates of aphasia, and resultant profiles of speech and language function.

Selection of neuropsychological tasks from a language test battery that optimally related to the function of each cortical area: Toward making a cognitive cortical map

We developed a cortical language map from performance data on a language test battery in patients with brain lesions. The research problem was how to select the subtest that was most related to the function of each cortical area from the battery. When studied by voxel-based lesion-symptom mapping (VLSM), patients were divided into two groups: those with and without a lesion at each particular region. We considered the task that optimally discriminated between the two groups to be the task most related to the function of a given region. One hundred and fifty left-lesioned patients were examined using the Japanese Standard Language Test of Aphasia (SLTA), which is composed of 26 subtests. Using logistic discriminant analysis, we selected the subtest that optimally discriminated the lesioned and non-lesioned groups for each cortical region. Patients with left middle frontal gyrus (area 46) lesions were optimally discriminated from patients without lesions in that area by the speech sound–kana letter choice matching subtest. Patients with lesions in the inferior postcentral gyrus were optimally distinguished by the disturbance of word repetition. Patients with lesions in the anterior cingulate gyrus were characterized by impaired performance on the category fluency subtest. Voxel-based discriminant analysis can thus select the subtest that can be regarded as most related to the function of each cortical area.

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From a cognitive test battery, we selected the subtest most related to the function of each cortical area.

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We conducted voxel-based lesion-symptom mapping using t-test and logistic regression.

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The t-statistic and G-statistic can be used as indicators of differences in task performance.

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This method is useful for clarifying the primary function of each region of cortex.

Health Related Quality of Life in Adult Low and High-Grade Glioma Patients Using the National Institutes of Health Patient Reported Outcomes Measurement Information System (PROMIS) and Neuro-QOL Assessments

Health related quality of life (HRQOL) measures have become increasingly important in the management of glioma patients in both research and clinical practice settings. Functional impairment is common in low-grade and high-grade glioma patients as the disease has both oncological and neurological manifestations. Natural disease history as well as medical or surgical treatment can negatively influence HRQOL. There are no universal standards for HRQOL assessment in glioma patients. In this study, we examine patient perspectives on functional outcome domains and report the prevalence of impairments rates using the National Institutes of Health (NIH) Patient Reported Outcomes Measurement Information System (PROMIS) and Neuro-QOL item banks as measures of HRQOL. Retrospective analysis of a prospectively collected dataset involving 79 glioma patients reveals that quality of life concerns are the most important consideration behind making decisions about treatment in 80.7% of patients. The prevalence of functional impairment by PROMIS and NEURO-QOL assessment is high, ranging from 28.6% in the physical function domain to 43.9% in the cognitive function domain. Pain and anxiety related to physical decline is higher in LGG patients compared to HGG patients. Aphasia severity also impacts HRQOL. The results of this study suggest that the PROMIS and NEURO-QOL assessments may be important HRQOL metrics for future use in larger clinical research and clinical trial settings.

A valid alternative for in-person language assessments in brain tumor patients: feasibility and validity measures of the new TeleLanguage test

BACKGROUND

Although language deficits after awake brain surgery are usually milder than post-stroke, postoperative language assessments are needed to identify these. Follow-up of brain tumor patients in certain geographical regions can be difficult when most patients are not local and come from afar. We developed a short telephone-based test for pre- and postoperative language assessments.

METHODS

The development of the TeleLanguage Test was based on the Dutch Linguistic Intraoperative Protocol and existing standardized English batteries. Two parallel versions were composed and tested in healthy native English speakers. Subsequently, the TeleLanguage Test was administered in a group of 14 tumor patients before surgery and at 1 week, 1 month, and 3 months after surgery. The test includes auditory comprehension, repetition, semantic selection, sentence or story completion, verbal naming, and fluency tests. It takes less than 20 minutes to administer.

RESULTS

Healthy participants had no difficulty performing any of the language tests via the phone, attesting to the feasibility of a phone assessment. In the patient group, all TeleLanguage test scores significantly declined shortly after surgery with a recovery to preoperative levels at 3 months postsurgery for naming and fluency tasks and a recovery to normal levels for the other language tasks. Analysis of the in-person language assessments (until 1 month) revealed a similar profile.

CONCLUSION

The use of the TeleLanguage battery to conduct language assessments from afar can provide convenience, might optimize patient care, and enables longitudinal clinical research. The TeleLanguage is a valid tool for various clinical and scientific purposes.

Parietal association deficits in patients harboring parietal lobe gliomas: a prospective study

OBJECTIVE

Although the parietal lobe is a common site for glioma formation, current literature is scarce, consists of retrospective studies, and lacks consistency with regard to the incidence, nature, and severity of parietal association deficits (PADs). The aim of this study was to assess the characteristics and incidence of PADs in patients suffering from parietal lobe gliomas through a prospective study and a battery of comprehensive neuropsychological tests.

METHODS

Between 2012 and 2016 the authors recruited 38 patients with glioma confined in the parietal lobe. Patients were examined for primary and secondary association deficits with a dedicated battery of neuropsychological tests. The PADs were grouped into 5 categories: visuospatial attention, gnosis, praxis, upper-limb coordination, and language. For descriptive analysis tumors were divided into high- and low-grade gliomas and also according to patient age and tumor size.

RESULTS

Parietal association deficits were elicited in 80% of patients, thus being more common than primary deficits (50%). Apraxia was the most common PAD (47.4%), followed by anomic aphasia and subcomponents of Gerstmann's syndrome (34.2% each). Other deficits such as hemineglect, stereoagnosia, extinction, and visuomotor ataxia were also detected, albeit at lower rates. There was a statistically nonsignificant difference between PADs and sex (72.2% males, 85% females) and age (77.8% at ≤ 60 years, 80% at age > 60 years), but a statistically significant difference between the > 4 cm and the ≤ 4 cm diameter group (p = 0.02, 94.7% vs 63.2%, respectively). There was a tendency (p = 0.094) for low-grade gliomas to present with fewer PADs (50%) than high-grade gliomas (85.7%). Tumor laterality showed a strong correlation with hemineglect (p = 0.004, predilection for right hemisphere), anomia (p = 0.001), and Gerstmann's symptoms (p = 0.01); the last 2 deficits showed a left (dominant) hemispheric preponderance.

CONCLUSIONS

This is the first study to prospectively evaluate the incidence and nature of PADs in patients with parietal gliomas. It could be that the current literature may have underestimated the true incidence of deficits. Dedicated neuropsychological examination detects a high frequency of PADs, the most common being apraxia, followed by anomia and subcomponents of Gerstmann's syndrome. Nevertheless, a direct correlation between the clinical deficit and its anatomical substrate is only possible to a limited extent, highlighting the need for intraoperative cortical and subcortical functional mapping.

Function-specific Tractography of Language Pathways Based on nTMS Mapping in Patients with Supratentorial Lesions

PURPOSE

In patients with supratentorial lesions diffusion tensor imaging fiber tracking (DTI-FT) is increasingly used to visualize subcortical fiber courses. Navigated transcranial magnetic stimulation (nTMS) was applied in this study to reveal specific cortical functions by investigating the particular language errors elicited by stimulation. To make DTI-FT more function-specific, the identified language-positive nTMS spots were used as regions of interest (ROIs).

METHODS

In this study 40 patients (mean age 53.8 ± 16.0 years) harboring language-eloquent left hemispheric lesions underwent preoperative nTMS language mapping. All induced error categories were separately defined as a ROI and used for function-specific nTMS-based DTI-FT. The fractions of patients showing various subcortical language-related pathways and the fibers-per-tract ratio (number of visualized fibers divided by the number of visualized tracts) were evaluated and compared for tractography with the single error types against less specific tractography including all identified cortical language sites (all errors except hesitations).

RESULTS

The nTMS-based DTI-FT using all errors except hesitations led to high fractions of visualized tracts (81.1% of patients), with a fibers-per-tract ratio of 538.4 ± 340.5. When only using performance errors, a predominant visualization of the superior longitudinal fascicle (SLF) occurred, which is known to be involved in articulatory processes. Fibers-per-tract ratios were comparatively stable for all single error categories when compared to all errors except hesitations (p > 0.05).

CONCLUSION

This is one of the first studies aiming on function-specific tractography. The results demonstrated that when using different error categories as ROIs, more detailed nTMS-based DTI-FT and, therefore, potentially superior intraoperative guidance becomes possible.

Neuropsychological outcome after subtemporal versus transsylvian approach for selective amygdalohippocampectomy in patients with mesial temporal lobe epilepsy: a randomised prospective clinical trial

OBJECTIVE

To compare the effects of different surgical approaches for selective amygdalohippocampectomy in patients with pharmacoresistant mesial temporal lobe epilepsy with regard to the neuropsychological outcome and to replicate an earlier study employing a matched-pair design.

METHOD

47 patients were randomised to subtemporal versus transsylvian approaches. Memory, language, attentional and executive functions were assessed before and 1 year after surgery. Multivariate analyses of variance (MANOVAs) with presurgical and postsurgical assessments as within-subject variables and approach and side of surgery as between-subject factors were calculated. Additionally, the frequencies of individual performance changes based on reliable change indices were analysed.

RESULTS

Seizure freedom International League Against Epilepsy (ILAE) 1a, was achieved in 62% of all patients without group difference. MANOVAs revealed no significant effects of approach on cognition. Tested separately for each parameter, verbal recognition memory declined irrespective of approach. Post hoc tests revealed that on group level, the subtemporal approach was associated with a worse outcome for verbal learning and delayed free recall as well as for semantic fluency. Accordingly, on individual level, more patients in the subtemporal group declined in verbal learning. Left side of surgery was associated with decline in naming regardless of approach.

CONCLUSION

The main analysis did not confirm the effects of approach on memory outcome seen in our previous study. Post hoc testing, however, showed greater memory losses with the subtemporal approach. Previous findings were replicated for semantic fluency. The discrepant results are discussed on the background of the different study designs.

The Control of Vocal Pitch in Human Laryngeal Motor Cortex

In speech, the highly flexible modulation of vocal pitch creates intonation patterns that speakers use to convey linguistic meaning. This human ability is unique among primates. Here, we used high-density cortical recordings directly from the human brain to determine the encoding of vocal pitch during natural speech. We found neural populations in bilateral dorsal laryngeal motor cortex (dLMC) that selectively encoded produced pitch but not non-laryngeal articulatory movements. This neural population controlled short pitch accents to express prosodic emphasis on a word in a sentence. Other larynx cortical representations controlling voicing and longer pitch phrase contours were found at separate sites. dLMC sites also encoded vocal pitch during a non-speech singing task. Finally, direct focal stimulation of dLMC evoked laryngeal movements and involuntary vocalization, confirming its causal role in feedforward control. Together, these results reveal the neural basis for the voluntary control of vocal pitch in human speech. VIDEO ABSTRACT.

Selective Interference with Syntactic Encoding during Sentence Production by Direct Electrocortical Stimulation of the Inferior Frontal Gyrus

Cortical stimulation mapping (CSM) has provided important insights into the neuroanatomy of language because of its high spatial and temporal resolution, and the causal relationships that can be inferred from transient disruption of specific functions. Almost all CSM studies to date have focused on word-level processes such as naming, comprehension, and repetition. In this study, we used CSM to identify sites where stimulation interfered selectively with syntactic encoding during sentence production. Fourteen patients undergoing left-hemisphere neurosurgery participated in the study. In 7 of the 14 patients, we identified nine sites where cortical stimulation interfered with syntactic encoding but did not interfere with single word processing. All nine sites were localized to the inferior frontal gyrus, mostly to the pars triangularis and opercularis. Interference with syntactic encoding took several different forms, including misassignment of arguments to grammatical roles, misassignment of nouns to verb slots, omission of function words and inflectional morphology, and various paragrammatic constructions. Our findings suggest that the left inferior frontal gyrus plays an important role in the encoding of syntactic structure during sentence production.

What Do Language Disorders Reveal about Brain-Language Relationships? From Classic Models to Network Approaches

Studies of language disorders have shaped our understanding of brain-language relationships over the last two centuries. This article provides a review of this research and how our thinking has changed over the years regarding how the brain processes language. In the 19th century, a series of famous case studies linked distinct speech and language functions to specific portions of the left hemisphere of the brain, regions that later came to be known as Broca's and Wernicke's areas. One hundred years later, the emergence of new brain imaging tools allowed for the visualization of brain injuries in vivo that ushered in a new era of brain-behavior research and greatly expanded our understanding of the neural processes of language. Toward the end of the 20th century, sophisticated neuroimaging approaches allowed for the visualization of both structural and functional brain activity associated with language processing in both healthy individuals and in those with language disturbance. More recently, language is thought to be mediated by a much broader expanse of neural networks that covers a large number of cortical and subcortical regions and their interconnecting fiber pathways. Injury to both grey and white matter has been seen to affect the complexities of language in unique ways that have altered how we think about brain-language relationships. The findings that support this paradigm shift are described here along with the methodologies that helped to discover them, with some final thoughts on future directions, techniques, and treatment interventions for those with communication impairments. (JINS, 2017, 23, 741-754).

Improving language mapping in clinical fMRI through assessment of grammar

Introduction

Brain surgery in the language dominant hemisphere remains challenging due to unintended post-surgical language deficits, despite using pre-surgical functional magnetic resonance (fMRI) and intraoperative cortical stimulation. Moreover, patients are often recommended not to undergo surgery if the accompanying risk to language appears to be too high. While standard fMRI language mapping protocols may have relatively good predictive value at the group level, they remain sub-optimal on an individual level. The standard tests used typically assess lexico-semantic aspects of language, and they do not accurately reflect the complexity of language either in comprehension or production at the sentence level. Among patients who had left hemisphere language dominance we assessed which tests are best at activating language areas in the brain.

Method

We compared grammar tests (items testing word order in actives and passives, wh-subject and object questions, relativized subject and object clauses and past tense marking) with standard tests (object naming, auditory and visual responsive naming), using pre-operative fMRI. Twenty-five surgical candidates (13 females) participated in this study. Sixteen patients presented with a brain tumor, and nine with epilepsy. All participants underwent two pre-operative fMRI protocols: one including CYCLE-N grammar tests (items testing word order in actives and passives, wh-subject and object questions, relativized subject and object clauses and past tense marking); and a second one with standard fMRI tests (object naming, auditory and visual responsive naming). fMRI activations during performance in both protocols were compared at the group level, as well as in individual candidates.

Results

The grammar tests generated more volume of activation in the left hemisphere (left/right angular gyrus, right anterior/posterior superior temporal gyrus) and identified additional language regions not shown by the standard tests (e.g., left anterior/posterior supramarginal gyrus). The standard tests produced more activation in left BA 47. Ten participants had more robust activations in the left hemisphere in the grammar tests and two in the standard tests. The grammar tests also elicited substantial activations in the right hemisphere and thus turned out to be superior at identifying both right and left hemisphere contribution to language processing.

Conclusion

The grammar tests may be an important addition to the standard pre-operative fMRI testing.

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We added comprehensive grammar tests to standard presurgical fMRI of language.

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The grammar tests generated more volume of activation bilaterally.

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The tests identified additional language regions not shown by the standard tests.

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The grammar tests may be an important addition to standard pre-operative fMRI.

Assessing the Amount of Spontaneous Real-World Spoken Language in Aphasia: Validation of Two Methods

PURPOSE

The purpose of this article is to present the results of a study evaluating the psychometric properties of 2 new measures that exclusively assess the amount of real-world spoken language in patients with aphasia.

METHOD

Forty individuals with aphasia were evaluated on several measures of spoken language in real-world settings. The Verbal Activity Log (VAL; Johnson et al., 2014) has participants, aided by caregivers, indicate current amount and quality of real-world spoken language compared with before stroke. In addition, digital voice recorders objectively measured the amount of real-world spoken language. The Communicative Effectiveness Index (Lomas et al., 1989), a previously validated measure of functional communication, was used as a comparison measure. Nineteen participants received follow-up assessment ≥ 3 weeks later.

RESULTS

Validity was supported by Pearson correlations between spoken language recordings and the VAL, r(38) = .70, p < .001. Likewise, correlation with the Communicative Effectiveness Index was strong, r(38) = .73, p < .001. Test-retest reliability for both VAL and audio recording was high, with intraclass correlations ≥ .96 and .90, respectively.

CONCLUSIONS

These results present preliminary evidence for the reliability and validity of the VAL and spoken language recording for assessment of the amount of real-world spoken language in aphasia. As a simple patient-reported outcome, the VAL may assist diverse therapies for aphasia.