MRI language dominance assessment in epilepsy patients at 1.0 T: region of interest analysis and comparison with intracarotid amytal testing

The primary goal of this study was to test the reliability of presurgical language lateralization in epilepsy patients with functional magnetic resonance imaging (fMRI) with a 1.0-T MR scanner using a simple word generation paradigm and conventional equipment. In addition, hemispherical fMRI language lateralization analysis and region of interest (ROI) analysis in the frontal and temporo-parietal regions were compared with the intracarotid amytal test (IAT). Twenty epilepsy patients under presurgical evaluation were prospectively examined by both fMRI and IAT. The fMRI experiment consisted of a word chain task (WCT) using the conventional headphone set and a sparse sequence. In 17 of the 20 patients, data were available for comparison between the two procedures. Fifteen of these 17 patients were categorized as left hemispheric dominant, and 2 patients demonstrated bilateral language representation by both fMRI and IAT. The highest reliability for lateralization was obtained using frontal ROI analysis. Hemispherical analysis was less powerful and reliable in all cases but one, while temporo-parietal ROI analysis was unreliable as a stand-alone analysis when compared with IAT. The effect of statistical threshold on language lateralization prompted for the use of t-value-dependent lateralization index plots. This study illustrates that fMRI-determined language lateralization can be performed reliably in a clinical MR setting operating at a low field strength of 1 T without expensive stimulus presentation systems.     

Translocation of Broca's area to the contralateral hemisphere as the result of the growth of a left inferior frontal glioma

We report a case of a patient with a left inferior frontal glioma in whom language functional magnetic resonance imaging (fMRI) paradigms produced activation of Broca's area on the right and Wernicke's area on the left. We propose that tumor invasion of the left frontal operculum led to cortical reorganization and interhemispheric transfer of Broca's area. This case emphasizes the importance of preoperative fMRI in assessing the location of eloquent cortices adjacent to a tumor and in guiding neurosurgical decision-making.     

失语症病人皮层语言活动的功能MRI初步研究

目的用功能磁共振成像(fMRI)技术研究失语症患者皮层语言功能状态，并探讨该技术临床应用的可行性。方法在6位健康志愿者和3位处于恢复阶段的失语症患者完成词汇联想任务的同时，用fMRI技术测量局部神经元活动引起的脑区信号改变，分析处理成代表语言功能区的统计激活图。结果6例正常志愿者的语言加工活动激活了1个由额叶、顶叶、颞叶和枕叶等许多脑区组成的神经网络。而失语症患者无论左侧额叶有无病变，均无左侧额叶下部的激活。此外，2位患者显示了右侧大脑半球某些区域的激活，而这些区域没有参与正常志愿者的语言加工。结论失语症患者皮层语言功能存在脑内局部病灶的远隔效应和皮层语言功能区的重新分布或重组现象。fMRI技术是评价失语症患者语言功能的有效方法。     

BOLD技术与皮质电刺激定位语言功能区的比较

目的:将语言BOLD与术中皮质电刺激作点对点比较,评价其对语言功能区定位的准确性.材料和方法:12例左侧大脑半球近语言功能区手术病例术前采用词语联想任务进行BOLD扫描,融合在导航序列上进行神经导航手术.在局麻下进行术中皮质电刺激,与导航影像对应,采用完全吻合或相邻1cm以内两种不同的标准来比较BOLD激活区与电刺激阳性区的关系.结果:12例病人共刺激了145个点,其中阳性点27个.与ESM比较,以完全重叠为标准,BOLD敏感性48.1%,特异性83.1%;以相距小于1cm为标准,BOLD敏感性88.9%,特异性75%.良性或低级别肿瘤(9例)BOLD敏感性(95.2%)特异性(80.4%)均高于高级别恶性肿瘤(3例)(敏感性66.7%,特异性68.6%).结论:词语联想任务的BOLD-fMRI与ESM结果有较好的吻合,显示出一定的临床应用价值.     

卒中后失语症的BOLD-fMRI研究初探

目的:应用血氧水平功能成像(blood oxygenation level dependent function MRI,BOLD-fMRI)研究卒中后失语的语言功能变化及修复。方法:运用BOLD-fMRI观察10例失语患者治疗前后脑功能区的受损情况及恢复情况。结果:在BOLD-fMRI图像上观察到治疗前语言优势半球激活减少,治疗后语言优势半球、非优势半球及小脑均有激活,以非优势半球及小脑激活为主,且激活区域大于治疗前激活区域。结论:BOLD-fMRI检查可观察到语言功能区域的漂移、代偿及修复。治疗前语言功能激活较少,治疗后主要由非优势半球及小脑代偿语言功能。     

Determination of hemisphere dominance for language: comparison of frontal and temporal fMRI activation with intracarotid amytal testing

The reliability of frontal and temporal fMRI activations for the determination of hemisphere language dominance was evaluated in comparison with intracarotid amytal testing (IAT). Twenty-two patients were studied by IAT (bilateral in 13, unilateral in 9 patients) and fMRI using a paradigm requiring semantic decisions. Global and regional (frontal and temporoparietal) lateralisation indices (LI) were calculated from the number of activated (r>0.4) voxels in both hemispheres. Frontolateral activations associated with the language task were seen in all patients, temporoparietal activations in 20 of 22. Regional LI corresponded better with IAT results than global LI. Frontolateral LI were consistent with IAT in all patients with bilateral IAT (including three patients with right dominant and one patient with bilateral language representation) and were not conflicting in any of the patients with unilateral IAT. Temporoparietal LI were discordant with IAT in two patients with atypical language representation. In the determination of hemisphere dominance for language, regional analysis of fMRI activation is superior to global analysis. In cases with clear-cut fMRI lateralisation, i.e. consistent lateralised activation of frontal and temporoparietal language zones, IAT may be unnecessary. FMRI should be performed prior to IAT in all patients going to be operated in brain regions potentially involved in language.     

Preoperative assessment of language areas in epileptic patients using functional MR imaging

ObjectiveTo determine the role of functional magnetic resonance imaging (fMRI) in assessing hemispheric language dominance in patients with epilepsy who are candidates for surgical treatment.Patients and methodsThis study was conducted on (14) consecutively enrolled epileptic patients (12 males, 2 females; mean age, 21 years; range 16–58 years) who were prospectively examined by the neurologist. Eleven (78.6%) patients were dominantly right handed, three (21.4%) were dominantly left handed. All of them underwent language assessment with fMRI and the results were compared with the intraoperative direct electrical stimulation mapping recordings.ResultsIn all the 14 epilepsy cases, language mapping data was concordant between fMRI and intraoperative direct electrocortical stimulation recordings for language dominance. However, fMRI mapping allowed for discrete, focal localization of regions involved in language processes whereas electrical recordings only delineated hemispheric dominance.ConclusionfMRI is considered as a powerful pre-surgical planning tool that has the potential to replace invasive and costly conventional methods. FMRI maps can easily be uploaded and used intra-operatively during stereotactic neurosurgery for accurate localization of complex brain functions.     

Clinical practice of language fMRI in epilepsy centers: a European survey and conclusions by the ESNR Epilepsy Working Group

To assess current clinical practices throughout Europe with respect to acquisition, implementation, evaluation, and interpretation of language functional MRI (fMRI) in epilepsy patients. An online survey was emailed to all European Society of Neuroradiology members (n = 1662), known associates (n = 6400), and 64 members of European Epilepsy network. The questionnaire featured 40 individual items on demographic data, clinical practice and indications, fMRI paradigms, radiological workflow, data post-processing protocol, and reporting. A total of 49 non-duplicate entries from European centers were received from 20 countries. Of these, 73.5% were board-certified neuroradiologists and 69.4% had an in-house epilepsy surgery program. Seventy-one percent of centers performed fewer than five scans per month for epilepsy. The most frequently used paradigms were phonemic verbal fluency (47.7%) and auditory comprehension (55.6%), but variants of 13 paradigms were described. Most centers assessed the fMRI task performance (75.5%), ensured cognitive-task adjustment (77.6%), trained the patient before scanning (85.7%), and assessed handedness (77.6%), but only 28.6% had special paradigms for patients with cognitive impairments. fMRI was post-processed mainly by neuroradiologists (42.1%), using open-source software (55.0%). Reporting was done primarily by neuroradiologists (74.2%). Interpretation was done mainly by visual inspection (65.3%). Most specialists (81.6%) were able to determine the hemisphere dominance for language in more than 75% of exams, attributing failure to the patient not performing the task correctly. This survey shows that language fMRI is firmly embedded in the preoperative management of epilepsy patients. The wide variety of paradigms and the use of non-CE-marked software underline the need for establishing reference standards.     

Clinical applications of functional magnetic resonance imaging

Despite its immediate success as a tool for basic research, the clinical application of functional MRI(fMRI) is still limited. FMRI has proven useful for presurgical functional mapping of the eloquent cortices. Localization of the sensorimotor cortex by fMRI may be of relatively limited value because the sensorimotor cortex can often be readily localized by means of anatomical methods. In contrast, the language cortices may not be localized anatomically and the language dominant hemisphere has been determined by invasive Wada test. Previous reports have shown that fMRI can be a promising alternative to the Wada test. A recent clinical trial has suggested that fMRI can be used to diagnose Alzheimer's disease in its earliest stage, detecting subclinical deterioration of the memory function. FMRI may be useful to predict the future decline of memory in people with genetic risks. Monitoring of the functional recovery of post-stroke brains may be another promising clinical application of fMRI. FMRI has demonstrated functional reorganization of the brain that may be related to the restoration of motor and language functions.     

Combined task activation display as an effective method to teach introductory fMRI users

Rationale and objectivesInterpreting functional magnetic resonance imaging (fMRI) can be an overwhelming and challenging task for trainees, particularly when post processing, synthesizing and interpreting data from multiple language paradigms. Currently, there is no established best method for teaching fMRI interpretation to new trainees. The purpose of our study is to compare the use of combined task activation display (CTAD) and conventional display of fMRI language paradigms as an effective method to teach fMRI to the introductory learner.Materials and methodsFollowing IRB approval, 43 unique cases (with 10 repeat cases to assess intra-reader variability) were identified based on the inclusion/exclusion criteria. Eight radiology trainees, without prior exposure to fMRI, were asked to determine language lateralization based on activation of Wernicke's area, Broca's area, and the pre-supplementary motor area. Prior to trainee interpretation, a 15-minute training session was conducted to describe the expected anatomic locations of the language centers. Trainees were asked to determine language dominance using either the CTAD or conventional methods. Following a 6-week washout period, the same eight trainees were asked to interpret the cases using the opposite interpretation approach.ResultsInterpreting fMRI with the CTAD method significantly increased trainee accuracy (85.4% vs 70.9% p < 0.001) and trainee confidence (4.3 vs 3.6 p < 0.001), while decreasing time to interpretation (mean difference of 29 min), and intra-reader variability when compared to the conventional approach.ConclusionCombined task activation display is an effective method to teach fMRI to introductory learners.     

Language and memory lateralization and localization using different fMRI paradigms in Arabic speaking patients: Initial experience

Purpose

Presurgical assessment of memory in patients with temporal lesions is essential to evaluate the effect of treatment on cognitive functioning (1). In recent years, there has been an increasing interest in the utility of functional MR imaging (fMRI) for presurgical evaluation of memory (2). There is no established fMRI protocol to evaluate memory functions presurgically (3). The identification of language areas in patients undergoing brain surgery is a major clinical challenge, the gold standard for the identification of essential language areas in neurosurgical patients is intraoperative mapping (IOM) by direct cortical stimulation as used by various groups but other techniques, such as functional imaging, are rapidly evolving (4). Language and also memory paradigms designed for patients speaking languages other than Arabic are not totally applicable for examining Arabic speaking and illiterate patients except after some modifications, the aim of this study is to test the applicability of these modified western designed paradigms for lateralization and localization of cortical brain centres concerned with language and memory in Arabic speaking patients.

Materials and methods

Using a 1.5 T Philips scanner, multiple modified western designed language and memory fMRI paradigms were used to assess the eloquent cortical brain areas in Arabic speaking patients of different levels of education having different lesions mainly brain tumors and epilepsy. These modifications consist mainly of providing simpler paradigms in an easy common Arabic language not in high level traditional Arabic, choosing simplified topics for the less educated patients, avoiding any written paradigms and depending on auditory paradigms in easy common Arabic language and simple pictures for illiterate patients. Images were analyzed using Philips extended MR work space release 2.5.3.0. The results were analyzed and compared to each other as regarding the patient cooperation and the ability to give robust fMRI signal.

Results

Multiple fMRI paradigms are efficient in lateralization and localization of cortical centres of language and memory yet they are variable in their ability to give robust fMRI signal clusters, also patients with different levels of education and culture differ in their ability to cooperate with the fMRI paradigms thus also affects the results.

Conclusion

Language and memory fMRI paradigms reported in the western literature are applicable to Arabic speaking patients with brain lesions undergoing an fMRI exam for language and/or memory but need some modifications according to background and level of education to get more robust identification of eloquent language and memory cortical centres.     

Functional MRI in symptomatic proliferative angiopathies

Seizures, the main expression of cerebral arteriovenous malformations (AVMs) can be difficult to control medically. We studied fMRI in correlation with clinical findings cerebral activation clusters patterns in relation with singular AVMs (proliferative angiopathy). We carried out blood oxygen-level dependent functional MRI (fMRI) in seven patients with language problems due to capillary ectasia with verbal fluency and repetition language tasks in box-car paradigms. fMRI maps were calculated with cross-correlation coefficients and superimposed on brain anatomy. Five patients had perimalformative and/or contralateral areas of ipsi- and contralateral activation clusters redistribution. One patient who underwent fMRI after a severe focal post-ictal deficit had total hemisphere contralateral activation clusters redistribution.     

Functional magnetic resonance imaging at 3T as a clinical tool in patients with intracranial tumors

Purpose: To investigate the potential of functional magnetic resonance imaging (fMRI) at 3T as a clinical tool in the preoperative evaluation of patients with intracranial tumors. High magnetic field strength such as 3T is of benefit for fMRI because signal-to-noise ratio and sensitivity to susceptibility changes are field-strength-dependent.

Material and Methods: Twenty patients with tumors close to eloquent sensorimotor or language areas were studied. Motor, sensory, and two language paradigms (word generation, rhyming) were used; their effectiveness was determined as the percentage of patients in whom the functional area of interest was activated. Activation maps were calculated and their quality rated as high, adequate, or insufficient. The influence of fMRI on the neurosurgical decision regarding operability, surgical approach, and extent of the resection, was assessed.

Results: Paradigm effectiveness was 90% for motor and 95% for sensory stimulation, and varied from 79% to 95% for word generation and rhyming in combination. Ninety percent of the activation maps held high or adequate quality. fMRI proved useful: in the decision to operate (9 patients), in the surgical approach (13 patients), and in extent of the resection (12 patients).

Conclusion: fMRI at 3T is a clinically applicable tool in the work-up of patients with intracranial tumors.     

Utilization of functional MRI language paradigms for pre-operative mapping: a systematic review

Neuroradiology - Functional MRI (fMRI) can be employed to non-invasively localize brain regions involved in functional areas of language in patients with brain tumour, for applications including...     

fMRI for preoperative neurosurgical mapping of motor cortex and language in a clinical setting

PURPOSE: Identification of the precentral gyrus can be difficult in patients with brain tumors. The purpose of the current study was to evaluate the clinical usefulness of functional MRI (fMRI) in identifying motor cortex and speech areas as a part of preoperative neurosurgical planning. METHOD: fMRI was performed using a 1.5 T MR unit in 41 patients with brain tumors. The motor paradigm was finger tapping and foot movement, whereas the language paradigm consisted of a two word semantic test. Statistical analysis of the data was done using the Kolmogorow-Smirnow test. Plots of signal intensities over time were created. RESULTS: The precentral gyrus was identified in 38 of 41 patients. In two patients, fMRI was not of acceptable quality due to motion artifacts. Speech areas were localized in 33 patients. In a typical clinical setting, the value of the method was graded "high." CONCLUSION: fMRI's efficacy in the preoperative localization of language and motor areas is high. The method should become a routine adjunct for preoperative evaluation of brain tumors in the near future.     

Resting-State Seed-Based Analysis: An Alternative to Task-Based Language fMRI and Its Laterality Index

BACKGROUND AND PURPOSE:Language is a cardinal function that makes human unique. Preservation of language function poses a great challenge for surgeons during resection. The aim of the study was to assess the efficacy of resting-state fMRI in the lateralization of language function in healthy subjects to permit its further testing in patients who are unable to perform task-based fMRI.MATERIALS AND METHODS:Eighteen healthy right-handed volunteers were prospectively evaluated with resting-state fMRI and task-based fMRI to assess language networks. The laterality indices of Broca and Wernicke areas were calculated by using task-based fMRI via a voxel-value approach. We adopted seed-based resting-state fMRI connectivity analysis together with parameters such as amplitude of low-frequency fluctuation and fractional amplitude of low-frequency fluctuation (fALFF). Resting-state fMRI connectivity maps for language networks were obtained from Broca and Wernicke areas in both hemispheres. We performed correlation analysis between the laterality index and the z scores of functional connectivity, amplitude of low-frequency fluctuation, and fALFF.RESULTS:Pearson correlation analysis between signals obtained from the z score of fALFF and the laterality index yielded a correlation coefficient of 0.849 (P < .05). Regression analysis of the fALFF with the laterality index yielded an R² value of 0.721, indicating that 72.1% of the variance in the laterality index of task-based fMRI could be predicted from the fALFF of resting-state fMRI.CONCLUSIONS:The present study demonstrates that fALFF can be used as an alternative to task-based fMRI for assessing language laterality. There was a strong positive correlation between the fALFF of the Broca area of resting-state fMRI with the laterality index of task-based fMRI. Furthermore, we demonstrated the efficacy of fALFF for predicting the laterality of task-based fMRI.

Brain surgery demands preservation of eloquent areas, including the language functional areas. Many studies have illustrated that fMRI is a noninvasive imaging technique that facilitates the lateralization of language function in individual patients.^1–3 The hemispheric language laterality index (LI) is estimated by evaluating the asymmetry in the activation of language areas in the right and left hemispheres of the human brain during a particular task.⁴ The ease of integrating fMRI with other MR imaging techniques allows the correct identification of pathology and its landmark with respect to language areas.^5–7During the acquisition of language fMRI, the subject is instructed to perform particular tasks designed to elicit a response from language functional areas. However, not all subjects, such as those with low intelligence quotients and pediatric patients, will be able to cooperate with the task-based fMRI. Resting-state fMRI (rsfMRI) is gradually evolving as an alternative to task-based fMRI. The rsfMRI technique extracts the low-frequency fluctuations in the blood oxygen level–dependent (BOLD) signal when subjects are instructed to lie relaxed inside the scanner.^7,8Tie et al⁹ extracted language networks from rsfMRI and evaluated the effectiveness of the automatic identification of language components by using independent component analysis. The study separated the activation patterns corresponding to the language network components from individual rsfMRI data. Another study adopted rsfMRI connectivity analysis to examine the degree of hemispheric dominance for language processing in healthy controls and patients with temporal lobe epilepsy.¹⁰ Functional connectivity (FC) analysis of the frontal cortex in the control group revealed a strong correlation with the LI. The authors found a good correlation between the LI and the epileptogenic mesial temporal lobe. Similarly, Pravatà et al¹¹ studied the correlation between the strength of FC between language networks and language performance in healthy controls and patients with epilepsy. They demonstrated an overall reorganization and reduction of the connectivity pattern within the language network of patients with intractable epilepsy. These studies evaluated the FC of language networks rather than regional abnormalities in the low-frequency fluctuations.In rsfMRI, the parameters FC, amplitude of low-frequency fluctuation (ALFF), and fractional amplitude of low-frequency fluctuation (fALFF) are used to examine the network-related and regional characteristics of low-frequency oscillations. FC analysis evaluates the correlation between the time courses of voxels in a seed region with every other region within the brain. The regions with strong correlations will be shown as an FC map.^7,12 ALFF and fALFF are rsfMRI metrics that help in identifying regional BOLD signal changes of rsfMRI fluctuations. ALFF quantifies the amplitude of the low-frequency fluctuations of rsfMRI BOLD signals. fALFF corresponds to the power spectrum of the low-frequency band with respect to all frequencies detectable with the applied time of repetition of the study.^13,14 Different studies reported the clinical application of these metrics.^13,15,16 However, none of the studies considered the accuracy of these metrics in determining the LI.^9–11The objective of our study was to determine the potential of rsfMRI to evaluate language lateralization in comparison with task-based fMRI. In the current study, we evaluated the z scores of FC, ALFF, and fALFF obtained via rsfMRI and assessed the correlations of each of these metrics with the LI of task-based fMRI from individual seed regions. We hypothesized that the metrics of seed-based rsfMRI analysis are strongly correlated with the LI obtained by using task-based fMRI. If this hypothesis is proved, then rsfMRI can be used instead of task-fMRI in patients who cannot perform the task.     

听觉性语言刺激的功能磁共振成像研究

目的用MR血氧水平依赖性(BOLD)技术研究听觉语言的功能磁共振成像(fMRI)。资料与方法23例受试者，其中正常志愿者14例，脑肿瘤患者6例，脑外伤软化灶形成患者3例。进行听觉性语言刺激共25次，采用BOLD技术进行相应脑功能区成像。结果所有受试者均能在MRI检查中表现出局部脑功能活动区规律的信号强度-时间变化曲线，并获得较清晰的图像。功能区附近的占位病变可造成局部功能区的移位和缩小等改变。结论BOLD-fMRI在活体人脑听觉语言的功能区定位方面是一种有效的方法。对需实施手术的颅内占位。病变进行BOLD-MRI检查对指导手术有价值。     

Mapping functionally related regions of brain with functional connectivity MR imaging

BACKGROUND AND PURPOSE: In subjects who are performing no prescribed cognitive task, functional connectivity mapped with MR imaging (fcMRI) shows regions with synchronous fluctuations of cerebral blood flow. When specific tasks are performed, functional MR imaging (fMRI) can map locations in which regional cerebral blood flow increases synchronously with the performance of the task. We tested the hypothesis that fcMRI maps, based on the synchrony of low-frequency blood flow fluctuations, identify brain regions that show activation on fMRI maps of sensorimotor, visual, language, and auditory tasks. METHODS: In four volunteers, task-activation fMRI and functional connectivity (resting-state) fcMRI data were acquired. A small region of interest (in an area that showed maximal task activation) was chosen, and the correlation coefficient of the corresponding resting-state signal with the signal of all other voxels in the resting data set was calculated. The correlation coefficient was decomposed into frequency components and its distribution determined for each fcMRI map. The fcMRI maps were compared with the fMRI maps. RESULTS: For each task, fcMRI maps based on one to four seed voxel(s) produced clusters of voxels in regions of eloquent cortex. For each fMRI map a closely corresponding fcMRI map was obtained. The frequencies that predominated in the cross-correlation coefficients for the functionally related regions were below 0.1 Hz. CONCLUSION: Functionally related brain regions can be identified by means of their synchronous slow fluctuations in signal intensity. Such blood flow synchrony can be detected in sensorimotor areas, expressive and receptive language regions, and the visual cortex by fcMRI. Regions identified by the slow synchronous fluctuations are similar to those activated by motor, language, or visual tasks.     

Implementations of clinical functional magnetic resonance imaging using character-based paradigms for the prediction of Chinese language dominance

PURPOSE: Recently, functional MRI (fMRI) using word generation (WG) tasks has been shown to be effective for mapping the Chinese language-related brain areas. In clinical applications, however, patients' performance cannot be easily monitored during WG tasks. In this study, we evaluated the feasibility of a word choice (WC) paradigm in the clinical setting and compared the results with those from WG tasks. METHOD: Intrasubject comparisons of fMRI with both WG and WC paradigms were performed on six normal human subjects and two tumor patients. Subject responses in the WC paradigm, based on semantic judgments, were recorded. Activation strength, extent, and laterality were evaluated and compared. RESULTS: Our results showed that fMRI with the WC paradigm evoked weaker neuronal activation than that with the WG paradigm in Chinese language-related brain areas. It was sufficient to reveal language laterality for clinical use, however. In addition, it resulted in less nonlanguage-specific brain activation. CONCLUSION: Results from the patient data demonstrated strong evidence for the necessity of incorporating response monitoring during fMRI studies, which suggested that fMRI with the WC paradigm is more appropriate to be implemented for the prediction of Chinese language dominance in clinical environments.