Presurgical Language fMRI in Children, Adolescents and Young Adults : A Validation Study

The long-term negative impact of childhood stroke on language

Objectives

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

Methods

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

Results

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

Conclusion

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

Non-Invasive Mapping of the Neuronal Networks of Language

This review consists of three main sections. In the first, the Introduction, the main theories of the neuronal mediation of linguistic operations, derived mostly from studies of the effects of focal lesions on linguistic performance, are summarized. These models furnish the conceptual framework on which the design of subsequent functional neuroimaging investigations is based. In the second section, the methods of functional neuroimaging, especially those of functional Magnetic Resonance Imaging (fMRI) and of Magnetoencephalography (MEG), are detailed along with the specific activation tasks employed in presurgical functional mapping. The reliability of these non-invasive methods and their validity, judged against the results of the invasive methods, namely, the "Wada" procedure and Cortical Stimulation Mapping (CSM), is assessed and their use in presurgical mapping is justified. In the third and final section, the applications of fMRI and MEG in basic research are surveyed in the following six sub-sections, each dealing with the assessment of the neuronal networks for (1) the acoustic and phonological, (2) for semantic, (3) for syntactic, (4) for prosodic operations, (5) for sign language and (6) for the operations of reading and the mechanisms of dyslexia.

Task-Based and Resting-State Functional MRI in Observing Eloquent Cerebral Areas Personalized for Epilepsy and Surgical Oncology Patients: A Review of the Current Evidence

Functional magnetic resonance imaging (fMRI) is among the newest techniques of advanced neuroimaging that offer the opportunity for neuroradiologists, neurophysiologists, neuro-oncologists, and neurosurgeons to pre-operatively plan and manage different types of brain lesions. Furthermore, it plays a fundamental role in the personalized evaluation of patients with brain tumors or patients with an epileptic focus for preoperative planning. While the implementation of task-based fMRI has increased in recent years, the existing resources and evidence related to this technique are limited. We have, therefore, conducted a comprehensive review of the available resources to compile a detailed resource for physicians who specialize in managing patients with brain tumors and seizure disorders. This review contributes to the existing literature because it highlights the lack of studies on fMRI and its precise role and applicability in observing eloquent cerebral areas in surgical oncology and epilepsy patients, which we believe is underreported. Taking these considerations into account would help to better understand the role of this advanced neuroimaging technique and, ultimately, improve patient life expectancy and quality of life.

Roles of fMRI and Wada tests in the presurgical evaluation of language functions in temporal lobe epilepsy

Surgical treatment of pharmacoresistant temporal lobe epilepsy (TLE) carries risks for language function that can significantly affect the quality of life. Predicting the risks of decline in language functions before surgery is, consequently, just as important as predicting the chances of becoming seizure-free. The intracarotid amobarbital test, generally known as the Wada test (WT), has been traditionally used to determine language lateralization and to estimate their potential decline after surgery. However, the test is invasive and it does not localize the language functions. Therefore, other noninvasive methods have been proposed, of which functional magnetic resonance (fMRI) has the greatest potential. Functional MRI allows localization of language areas. It has good concordance with the WT for language lateralization, and it is of predictive value for postsurgical naming outcomes. Consequently, fMRI has progressively replaced WT for presurgical language evaluation. The objective of this manuscript is to review the most relevant aspects of language functions in TLE and the current role of fMRI and WT in the presurgical evaluation of language. First, we will provide context by revising the language network distribution and the effects of TLE on them. Then, we will assess the functional outcomes following various forms of TLE surgery and measures to reduce postoperative language decline. Finally, we will discuss the current indications for WT and fMRI and the potential usefulness of the resting-state fMRI technique.

Noninvasive Prediction of Language Lateralization Through Arcuate Fasciculus Tractography in Patients With Low-Grade Gliomas: Correlation With The Wada Test

Language lateralization is unique to humans, so clarifying dominant side is helpful for removing gliomas involving language areas. This study investigated the arcuate fasciculus (AF) reconstructed by diffusion tensor imaging–based tractography (DTT) in predicting language lateralization in patients with low-grade gliomas. Wada test was performed to determine the language Dominant Hemisphere (DH) and the Contralateral Hemisphere. DTI data [1.5-T magnetic resonance imaging (MRI)] was used to reconstruct AF by two independent operators using a DTT method. Fiber number, volume, and fractional anisotropy (FA) of bilateral reconstructed AF were measured. Lateralization indexes (LIs), including Number Index (NI), Volume Index (VI), and FA Index (FI), were accordingly calculated by mean values. A total of 21 patients with WHO Grade II gliomas in the left hemisphere were included. Every patient received a successful Wada test and reconstruction of bilateral AF. DTT metrics of reconstructed AF, such as fiber number, volume, and FA, showed significantly asymmetric between hemispheres. All the LI (NI, VI, and FI) values were statistically higher in the DH determined by the Wada test. No discrepancy was found between the prediction using the cutoff values of DTT metrics and the results of WADA test. The Kappa values were 0.829, 0.696, and 0.611, indicating NI and VI as more reliable predictor than FI although FI itself may also be feasible. Compared with the Wada test, we consider that DTT of AF is a non-invasive, simple, relatively accurate, and feasible method in predicting language lateralization in patients with low-grade gliomas.

Cognitive development after perinatal unilateral infarctions: No evidence for preferential sparing of verbal functions

BACKGROUND

Even children with extensive perinatal left-sided lesions have been reported to show normal language functions based on right-hemispheric language reorganization. This reorganization can lead to deficits in originary right hemispheric functions ("crowding hypothesis"). In a previous study, however, we identified epilepsy (even when well-controlled), and not language reorganization, as the major risk factor for impaired nonverbal functions. Here, we asked whether verbal and nonverbal functions develop differently, and whether they share the same risk factors.

METHODS

We investigated 23 patients (11f, Md = 12.56 years) with perinatal strokes (16 left-sided, 8 with epilepsy), and 23 healthy age-matched controls (8 f, Md = 12.42years). Language functions were assessed using the Potsdam Illinois Test of Psycholinguistic Abilities, nonverbal intelligence with the Test of Nonverbal Intelligence, language lateralization with functional MRI, and lesion size with MRI-based volumetry.

RESULTS

We found no systematic difference between verbal and nonverbal skills in our patients or controls [median difference Z(PITPA)-Z(TONI): patients = -0.03, controls = -0.06]. Accordingly, verbal and nonverbal functions were strongly correlated in patients (r = 0.80) and in controls (r = 0.74). Language ability correlated significantly with epilepsy. Furthermore, in patients with epilepsies, verbal skills were significantly lower than in controls.

CONCLUSION

In our cohort, we found no evidence for a differential effect of perinatal strokes on the development of verbal versus nonverbal functions, and, specifically, no evidence for a preferential sparing of verbal functions. Epilepsy, even when well-controlled, was confirmed as a single key risk factor for verbal functions.

Clinical Speech fMRI in Children and Adolescents : Development of an Optimal Protocol and Analysis Algorithm

Purpose

In patients with drug-resistant focal epilepsy, surgical resection is often the only treatment option to achieve long-term seizure control. Prior to brain surgery involving potential language areas, identification of hemispheric language dominance is crucial. Our group developed and validated a functional magnetic resonance imaging (fMRI) battery of four pediatric language tasks. The present study aimed at optimizing fMRI data acquisition and analysis using these tasks.

Methods

We retrospectively analyzed speech fMRI examinations of 114 neuropediatric patients (age range 5.8–17.8 years) who were examined prior to possible epilepsy surgery. In order to evaluate hemispheric language dominance, 1–4 language tasks (vowel identification task VIT, word-chain task WCT, beep-story task BST, synonym task SYT) were measured.

Results

Language dominance was classified using fMRI activation in the 13 validly lateralizing ROIs (VLR) in frontal, temporal and parietal lobes and cerebellum of the recent validation study from our group: 47/114 patients were classified as left-dominant, 34/114 as bilateral and 6/114 as right-dominant. In an attempt to enlarge the set of VLR, we then compared for each task agreement of these ROI activations with the classified language dominance. We found four additional task-specific ROIs showing concordant activation and activation in ≥ 10 sessions, which we termed validly lateralizing (VLR_new). The new VLRs were: for VIT the temporal language area and for SYT the middle frontal gyrus, the intraparietal sulcus and cerebellum. Finally, in order to find the optimal sequence of measuring the different tasks, we analyzed the success rates of single tasks and all possible task combinations. The sequence 1) VIT 2) WCT 3) BST 4) SYT was identified as the optimal sequence, yielding the highest chance to obtain reliable results even when the fMRI examination has to be stopped, e.g., due to lack of cooperation.

Conclusion

Our suggested task order together with the enlarged set of VLR_new may contribute to optimize pediatric speech fMRI in a clinical setting.

Supplementary Information

The online version of this article (10.1007/s00062-021-01097-z) contains supplementary material, which is available to authorized users.

Perspectives on (A)symmetry of Arcuate Fasciculus. A Short Review About Anatomy, Tractography and TMS for Arcuate Fasciculus Reconstruction in Planning Surgery for Gliomas in Language Areas

Gliomas are brain tumors that are treated with surgical resection. Prognosis is influenced by the extent of resection and postoperative neurological status. As consequence, given the extreme interindividual and interhemispheric variability of subcortical white matter (WM) surgical planning requires to be patient's tailored. According to the “connectionist model,” there is a huge variability among both cortical areas and subcortical WM in all human beings, and it is known that brain is able to reorganize itself and to adapt to WM lesions. Brain magnetic resonance imaging diffusion tensor imaging (DTI) tractography allows visualization of WM bundles. Nowadays DTI tractography is widely available in the clinical setting for presurgical planning. Arcuate fasciculus (AF) is a long WM bundle that connects the Broca's and Wernicke's regions with a complex anatomical architecture and important role in language functions. Thus, its preservation is important for the postoperative outcome, and DTI tractography is usually performed for planning surgery within the language-dominant hemisphere. High variability among individuals and an asymmetrical pattern has been reported for this WM bundle. However, the functional relevance of AF in the contralateral non-dominant hemisphere in case of tumoral or surgical lesion of the language-dominant AF is unclear. This review focuses on AF anatomy with special attention to its asymmetry in both normal and pathological conditions and how it may be explored with preoperative tools for planning surgery on gliomas in language areas. Based on the findings available in literature, we finally speculate about the potential role of preoperative evaluation of the WM contralateral to the surgical site.

Non-verbal Intelligence in Unilateral Perinatal Stroke Patients With and Without Epilepsies

Background: The risk factors for impaired cognitive development after unilateral perinatal stroke are poorly understood. Non-verbal intelligence seems to be at particular risk, since language can shift to the right hemisphere and may thereby reduce the capacity of the right hemisphere for its originary functions. Pharmaco-refractory epilepsies, a frequent complication of perinatal strokes, often lead to impaired intelligence. Yet, the role of well-controlled epilepsies is less well-understood. Here, we investigated whether well-controlled epilepsies, motor impairment, lesion size, lesion side, and lateralization of language functions influence non-verbal functions. Methods: We recruited 8 patients with well-controlled epilepsies (9-26 years), 15 patients without epilepsies (8-23 years), and 23 healthy controls (8-27 years). All underwent the Test of Non-verbal Intelligence, a motor-independent test, which excludes biased results due to motor impairment. Language lateralization was determined with functional MRI, lesion size with MRI-based volumetry, and hand motor impairment with the Jebson-Taylor Hand Function-Test. Results: Patients with epilepsies showed significantly impaired non-verbal intelligence [Md = 89.5, interquartile range (IQR) = 13.5] compared with controls (Md = 103, IQR = 17). In contrast, patients without epilepsies (Md = 97, IQR = 15.0) performed within the range of typically developing children. A multiple regression analysis revealed only epilepsy as a significant risk factor for impaired non-verbal functions. Conclusion: In patients with unilateral perinatal strokes without epilepsies, the neuroplastic potential of one healthy hemisphere is able to support the development of normal non-verbal cognitive abilities, regardless of lesion size, lesion side, or language lateralization. In contrast, epilepsy substantially reduces this neuroplastic potential; even seizure-free patients exhibit below-average non-verbal cognitive functions.