RPS 1611 - Functional MRI and diffusion tensor imaging

RPS 1611-1
Resting-state functional magnetic resonance imaging in predicting the long-term functional outcome after acute ischaemic stroke
Purpose: Stroke is one of the main causes of disability in adults. Resting-state functional magnetic resonance imaging (rs-fMRI) is able to map functional-anatomic networks by analysing spontaneously correlated low-frequency activity fluctuations across the brain. However, the role of rs-fMRI to predict the functional outcome after acute stroke remains unclear. We aimed to evaluate the impact of rs-fMRI at 72h after stroke symptoms onset to predict the functional outcome at 1-year follow-up.
Methods: 35 reperfused stroke patients (12 female, age: 68±14 years, 3-day national institutes of health stroke scale (NIHSS) score: 6±5) were consecutively scanned 72 hours after symptom onset. A modified Rankin scale (mRS) was used to evaluate functional outcome at 90 days (patients with good functional outcome, mRS ?2; poor outcome, mRS>2). Image pre-processing included motion and slice-timing correction, outliers? detection, brain tissue segmentation, MNI space normalisation, smoothing, and band-pass filtering to remove undesired components. Region-of-interest analyses were performed to calculate the correlation coefficients for every pairwise region and a weighted general linear model was used to discover significative differences (p<0.05 FWE) between groups.
Results: Patients with good outcome presented higher intra-network connectivity, while patients with poor outcome showed lower inter-network connectivity. To predict the 1-year functional outcome after a stroke, the 3-day NIHSS score was the most relevant predictor. An accuracy of 74.3% was obtained through a discriminant model using only clinical scores. Adding anatomical networks increased accuracy to 88.6%, 97.1% (including functional networks), and 100% (with clinical and imaging variables).
Conclusion: These results show the relevance of rs-fMRI in the acute phase to predict the long-term functional outcome in stroke patients.
Limitations: The sample size.
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-2
The application of resting and task state fMRI in common exotropia (recorded)
Purpose: This study applied brain resting and task state fMRI to detect the changes of brain activity and explore the mechanism of neurological damage in adult patients with common exotropia.
Methods: 20 patients (M:10, F:10) and 20 age- and sex-matched controls with normal corrected visual acuity from 18 to 26 years of age were enrolled in this study. Two independent samples t-tests were employed to measure the differences of regional homogeneity (ReHo) and amplitude of low-frequency fluctuation (ALFF) in the resting-state fMRI and the brain-activity difference in the visual stimuli task fMRI of two groups.
Results: Compared with healthy controls, patients had significantly higher ReHo in the right middle occipital gyrus and the left supramarginal gyrus, and lower values in the right cingulate gyrus, the right precentral gyrus, the right superior temporal gyrus, and the left frontal sub-gyral lobe (P<0.05). Patients showed a reduced ALFF in the left superior parietal lobe, the right middle cingulate gyrus, the left anterior cingulate gyrus, and the right inferior temporal gyrus (P<0.05). Moreover, under the condition of binocular 2D visual task stimulus, the brain activity increased in the left superior frontal gyrus, the right superior orbital frontal gyrus, the bilateral inferior orbital frontal gyrus, and the left rectus gyrus in the patient group. Meanwhile, the brain activity of the left postcentral gyrus and the left precuneus gyrus increased under binocular stereo-stimulation.
Conclusion: Common exotropia may lead to disorders in the processing of visual-spatial information and the control of emotion and attention.
Limitations: The small case sample.
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-3
BOLD fMRI mapping of the language network: comparative assessment of task-based and resting-state fMRI
Purpose: Task-based fMRI is the method of choice for determining the hemispheric dominance of language function. One important limitation is that the technique depends on the patient?s ability to perform the task.
The aim of our study was to test the feasibility of using resting-state fMRI instead of task-based approaches.
Methods: 15 healthy native English speakers underwent resting-state fMRI and two language fMRI paradigms: a verbal fluency (VF) and one verb generation (VG).
Task-based fMRI was analysed using both a general linear model (GLM) in the SPM software and independent component analysis (ICA).
Resting-state fMRI data was analysed by using both ICA and principal component analysis (PCA) using the SPM CONN toolbox, assuming a fixed number of 20 components. Resting-state networks were extracted by using both an automated template procedure and visually by two experts (VL and LM).
Results: The VG paradigm was more accurate than the VF paradigm or combination of the two and was therefore selected for further analyses.
Some of the networks labelled as language networks by the software were considered inappropriate and discarded by the experimenters.
There was a poor overlap between resting-state and task-related areas of activation as assessed by calculating the Dice similarity coefficients (mean: 0.1815) using the masks from the VG task GLM analysis, and the selected resting-state components.
The laterality index (LI) values of resting-state networks were significantly lower (mean: -0.0165) than the LI of the VG task map (0.4846).
Conclusion: Our results do not support the use of resting-state fMRI instead of task-based fMRI for hemispheric dominance assessment.
Limitations: Our sample is relatively small and heterogenous.
Ethics: Written informed consent was obtained from all subjects.
Funding: This work was part of the UCLH Project ID number: 09/H0716/18.
RPS 1611-4
Machine learning analysis in the diagnosis of medication overuse headache: a resting-state functional magnetic resonance imaging study (recorded)
Purpose: Medication-overuse headache (MOH) is a psychiatric comorbidity associated with chronic migraine. As machine learning is capable of identifying subtle disease patterns on a single subject level, we sought to determine the differences between MOH patients from healthy controls by using a machine learning classifier on resting-state functional MRIs (rs-fMRI).
Methods: 34 patients with MOH and 41 age and sex-matched healthy controls were recruited. Smooth mean regional homogeneity (smReHo) was obtained via DPARSFA. Support vector machine (SVMs) algorithms based on PRoNTo toolbox were used to explore the utility for smReHo in the differentiation of patients and controls individually. Finally, Pearson's correlation between the MOH patients and clinical measurement was investigated.
Results: The balanced accuracy of the correct classification of MOH and controls was 72.03% for smReHo (p<0.001 during 1,000 permutation testing). Areas contributing to classification accuracy mainly included in right Heschl's gyrus (3.23%), left temporal pole, and right inferior temporal gyrus. The direct comparison showed that MOH patients had significantly decreased smReHo activation in the right Heschl's gyrus (p<0.05, FDR corrected), which was corresponding to the highest weight area by machine learning classifier. A negative correlation was observed between the duration of medication intake and smReHo activation in the right Heschl's gyrus (r=-0.433, p<0.05).
Conclusion: With machine learning computational analyses, our study was able to diagnose MOH patients on a single subject level by demonstrating decreased regional function in MOH patients, notably involving the right Heschl's gyrus, suggesting the right Heschl's gyrus might play an important role in the pathogenesis of MOH.
Limitations: Studies with larger samples may be required for further verification.
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-5
The reorganisation of language networks after temporal lobe epilepsy surgery: a clinical fMRI study
Purpose: The reorganisation of language is common in epilepsy patients and a relevant factor in surgical therapy. The non-invasive gold standard in presurgical evaluation is language fMRI. fMRI network analysis could reveal subtle changes in language network architecture so far invisible with standard analyses and thus provide relevant additional information. We aimed to investigate the reorganisation processes of language networks in surgical patients with temporal lobe epilepsy (TLE) using standard fMRI activation and recent network analysis.
Methods: Task-based language fMRIs were performed on 28 TLE patients (16 right/12 left) before and after surgery, and on 22 healthy controls. FMRI activation analysis, a derived laterality index, and functional connectivity of global and language networks were used to investigate language architecture. Naming, semantic, and phonematic verbal fluency were correlated with imaging parameters.
Results: Both left and right TLE were associated with widespread language network alterations, particularly ipsilesional, before, and more pronounced after surgery. Preoperatively, mesiotemporal connectivity was decreased in left TLE, while postoperatively bihemispheric changes with a shift to more atypical language laterality (especially frontal) occurred. In right TLE, right intrahemispheric frontotemporal functional connectivity was attenuated before and further decreased after surgery, while those patients with stronger connectivity scored worse in semantic verbal fluency. Better postoperative naming ability was generally accompanied by stronger interhemispheric frontal connectivity. In all cases, network analysis revealed more widespread alterations than activation analysis.
Conclusion: The reorganisation of language function is a visualisable phenomenon in left and right TLE, both before and after surgery. Functional connectivity analysis reveals more widespread network changes than fMRI activation analysis and may offer a more comprehensive view on language architecture. Some connectivity measures may serve as biomarkers for language performance.
Limitations: n/a
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-6
Dynamic functional connectivity alterations of trigeminal neuralgia in resting-state fMRIs (recorded)
Purpose: Functional connectivity abnormalities, such as default mode network (DMN), have been reported previously in trigeminal neuralgia (TN) of which chronic pain is a common symptom. However, little is known about the dynamic functional connectivity (dFC) in patients with TN.
Methods: 29 patients with TN were enrolled in this study and underwent rest-functional MRI scanning along with 24 age-, sex-, and education-matched healthy control (HC) subjects. A sliding-window approach was used to study the dFC based on the GIFT (group ICA of fMRI toolbox).
Results: The functional networks were arranged into DMN, auditory network (AUD), visual network (VIS), and ventral attention network (VAN). Dynamic analysis suggested 4 distinct connectivity ?states? across the entire group (state I for 24%, state II for 16%, state III for 35%, and state IV for 25%) and a larger proportion of state III and a smaller proportion of state IV were observed compared with HC group (p=0.0000 and p=0.0058, respectively). Furthermore, the TN group showed decreased connections between networks (DMN-VIS, AUD-VIS, and VIS-VAN). Our analyses showed that increased dwell time in the state IV was associated with the presence of pain in TN.
Conclusion: Our study indicates that chronic pain in TN is characterised by altered temporal properties in dynamic connectivity. Further studies on dynamic functional connectivity could help to better understand the progressive dysfunction of networks in TN.
Limitations: Correlation analysis is in progress.
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-7
Resting-state network plasticity in low-grade glioma patients before and after resection: maintaining language skills
Purpose: Diffuse low-grade gliomas (DLGG) have a slow infiltrating character, allowing for simultaneous plasticity and maintaining the patients? functional capacity. Here we addressed whether and how anatomical disconnection following left-hemispheric DLGG growth and resection interferes with resting-state connectivity, specifically in relation to language.
Methods: 39 native French persons with a left DLGG were included and underwent awake surgical resection of the tumour. The anatomical disconnectivity risk following the DLGG volume and the resection, and the functional connectivity of resting-state fMRI images in relation to language, were evaluated prior to and three months after surgery. Resting-state connectivity patterns were compared with 19 healthy controls. Language was assessed with a picture-naming task.
Results: Adaptive plasticity was observed in regions around the tumour/cavitas area, with increased connectivity of the left and right inferior parietal lobule with the left inferior temporal gyrus. Picture naming was surprisingly not dependent on the connectivity of the language network, but of the connectivity of regions know to be involved in semantics, in which their specific role could be explained in the light of the broader resting-state network they took part in. Also, the recruitment of the frontoparietal attention network was observed.
Conclusion: A whole-brain approach with specific clinical data input is required for meaningful resting-state analysis in case of lesions. Pre-surgical local plasticity and functional compensation by increased task-directed attention allow a relative high level of performance maintenance after DLGG resection.
Limitations: All participants underwent intensive speech-language rehabilitation post-surgery, which might have trained and strengthened attentional resources. The compensational strategy might thus have been learned.
Ethics: The study received local ethical committee?s approval. Participants gave informed consent.
Funding: LabEx NUMEV (n° AN-10-LABX-20) and CHU Montpellier (AOI n° 2010-A01313-36).
RPS 1611-8
Thalamic structural connectivity abnormalities in minimal hepatic encephalopathy: a probabilistic tractography study (recorded)
Purpose: There have been accumulating studies demonstrating thalamic related structural, functional, and metabolic abnormalities in minimal hepatic encephalopathy (MHE). We conducted the first study to investigate thalamic-related structural connectivity alterations in MHE.
Methods: Diffusion based probabilistic tractography was used to determine the structural connection between the thalamus and the cortical/subcortical regions in 22 cirrhotic patients with MHE, 30 cirrhotic patients without MHE (NHE), and 30 healthy controls. DTI (diffusion tensor imaging) measurements of these thalamic connections, including connectivity strength (CS), fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), were calculated and compared across three groups. Neuropsychological assessment was performed as well. The correlation analysis was conducted to investigate the relationship between neuropsychological performance and the measurements about thalamic connections. Machine-learning classification analysis was performed to estimate whether diffusion measurements can distinguish MHE from NHE.
Results: The probabilistic tractography revealed thalamic structural connection, which was disturbed in cirrhotic patients (reflected by decreased CS/FA and increased MD/AD/RD). Abnormal thalamic connection primarily involved the prefrontal cortex, sensorimotor cortex, parietal cortex, medial temporal cortex, hippocampus, and striatum. Thalamic connectivity abnormalities deteriorated from NHE to MHE and correlated with patients? impaired neuropsychological performance. The relatively high classification accuracy was obtained using CS as a discriminating index.
Conclusion: Our results demonstrated the altered thalamic structural connectivity with both cortical and subcortical regions in MHE. The disturbed thalamic connectivity may underlie the mechanism about cognitive deficits in MHE and can serve as biomarker for the diagnosis of MHE and monitoring disease progression.
Limitations: The cross-sectional design.
Ethics: The Research Ethics Committee of Fujian Medical University Union Hospital, China.
Each subject provided a written informed consent.
Funding: The National Natural Science Foundation of China (No.81501450).
RPS 1611-9
Assessment of translingual neurostimulation in the treatment of children with cerebral palsy in the late residual stage by means of a functional MRI
Purpose: Constant stimulation of the nervous system is one of the most popular ways to activate neural networks in order to activate the brain and initiate neuroplasticity processes. The purpose of the study was to evaluate the impact of translingual neurostimulation of the brain to balance, coordination of movement, and the ability to form new motor skills in children with cerebral palsy in the late residual stage.
Methods: This study involved 6 children with cerebral palsy, a form of spastic diplegia. Patients had intact intellect and no seizures in anamnesis. All children received standard treatment, including massage, medical-gymnastics with simulators, 10 daily sessions of physical therapy and neurostimulation of the brain (using a device for electrotactile stimulation called PoNS (portable neurostimulator)).
Patients underwent functional MRI of the brain before the start of, and at the end of, the course of treatment. The research was carried out using movement functional paradigms for each extremity (both feet and hands) and an active ?count? paradigm for patients who could perform the task for the count and depending on clinical status, and passive movement or sensory paradigms were performed for those who could not. Postprocessing was carried out using the software package SPM 12.
Results: All patients noted decreased muscle tone and improved balance and coordination functions after neurostimulation. According to obtained fMRI data, patients who underwent translingual neurostimulation showed increased activation in the right-hand motor area and activation in the foot motor area in response to the stimuli.
Conclusion: Translingual neurostimulation is innovative in the field of neurostimulation, non-invasive, and safe and easy to use. fMRI active paradigms, with proper and high-quality implementation, is an auxiliary method for the objective control of treatment efficiency.
Limitations: n/a
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-10
Altered structural and functional connectome in unilateral sudden sensorineural hearing loss
Purpose: To investigate the alterations of brain structural and functional connectome in unilateral sudden sensorineural hearing loss (USSHL) patients.
Methods: We constructed functional-structural connectomes for USSHL patients (41 for the left side and 44 for the right side) and 85 controls. Graph theoretical analysis was employed to evaluate the network properties of functional-structural brain connectome. Moreover, we quantified coupling between functional-structural connectome by the correlation between functional-structural connectome edges within non-zero structural connectivity areas. The coupling of functional-structural brain connectome was compared by using permutation tests. To investigate the clinical relevance of altered brain network topologies in USSHL, Pearson's correlation analysis was performed between the clinical variables and the topological properties.
Results: Compared with the control groups, both groups of USSHL patients exhibited a significantly increased clustering coefficient, global efficiency, and local efficiency, but a significantly decreased characteristic path length in functional brain connectome, while a significant decrease clustering coefficient and local efficiency in structural brain connectome. In addition, the primary increased nodal strength was observed in limbic and paralimbic systems primarily as well as in the auditory network brain areas. More importantly, the coupling strength of structural-functional connectome was decreased and exhibited a negative correlation with some USSHL clinical variables in patients.
Conclusion: Detectable alteration of network organisation already occurred in USSHL patients within the acute period at the global and regional level. The functional connectome is characterised by a shift toward small-worldization while the structural connectome is toward randomisation, which may indicate a plastic reorganisation procedure of the brain to compensate for the loss of hearing in USSHL. Moreover, the degree of coupling between structural-functional connectome was decreased, which may reflect the pathophysiological mechanisms of USSHL.
Limitations: n/a
Ethics: n/a
Funding: NSFC (81701673).
RPS 1611-11
On the relevance of functional-structural correlations in the multimodal MRI workup of neurosurgical cases
Purpose: To investigate whether multimodal network graph analyses are relevant in the discussion of the combined fMRI-DTI pre-surgical evaluation of language networks.
Methods: A retrospective cross-sectional evaluation of our 39 consecutive patients who underwent pre-surgical BOLD fMRI with 4 language tasks (TR=3s, 3x3x3 mm voxels) was conducted. DTI (32 encoding directions, b=800 s/mm2, 2 mm isotropic resolution) was done with a standard SPM12 (https://www.fil.ion.ucl.ac.uk/spm) pipeline for fMRI, with the resulting activation maps further analysed using ICN_Atlas (Kozák et al., NeuroImage, 2017) with AAL atlas ROIs (Tzourio-Mazoyer et al., Neuroimage, 2002). DTI data was analysed using ExploreDTI with whole-brain tractography (Leemans et al., ISMRM, 2009) resulting in AAL-based connectivity matrices. Structural connectiome characteristics calculated with the brain connectivity toolbox (Rubinov and Sporns, NeuroImage, 2010) were compared against fMRI-based language network parameters using conventional parametric statistics in Matlab, focusing on Broca?s and Wernicke?s areas bilaterally.
Results: fMRI lateralisation correlated significantly with structural connectome graph parameters in a task-dependent fashion. The temporal lateralisation of speech comprehension and auditory decision and the frontal lateralisation of picture naming and synonym decision showed significant positive correlations with network metrics-based lateralisation parameters of the temporoparietal areas. The lateralisation of frontal language areas was also reflected in the lateralisation of arcuate fasciculus (AF).
Conclusion: The temporal lobe language networks seem to have a defining role in whole-brain language organisation, shown by the observed functional-structural correlations that are in line with previous literature (Wylie and Regner, Neurosci, 2014; Propper er al., Brain Cogn, 2010). A proper multimodal presurgical workup is important for preserving language function.
Limitations: The heterogeneity of age and pathologies, and DTI data instead of HARDI.
Ethics: Semmelweis University IRB #153/2019 (retrospective cross-sectional).
Funding: NRDIO Hungary OTKA-K128040 [LRK, GG]; EFOP-3.6.3-VEKOP-16-2017-00009, ÚNKP-19-3-III [GG].
RPS 1611-12
Diffusion tensor tractography (DTT): an objective method of determining clinically relevant, compressive, spinal cord myelopathy
Purpose: Magnetic resonance imaging (MRI) is the gold-standard imaging tool for compressive spinal cord myelopathy (CSCM). Diffusion tensor imaging (DTI), especially fibre-tracking or tractography (DTT), has been considered superior to routine MRI in predicting prognosis and urgency of decompression. This study aims to evaluate DTT as an advanced dimension of MRI in patients with CSCM in predicting the necessity of decompression management.
Methods: 12 patients with clinical signs of CSCM underwent conventional MRI and DTI examination with a high-resolution matrix on a 1.5T magnet system. 3D-colour-coded maps were obtained in the sagittal and coronal planes. The presence or absence of parenchymal signal alteration and change in colour-code of the neural fibre tracts in the spinal cord, in addition to the integrity and homogeneous thickness of the fibre tracts on DTT, was evaluated.
A near-homogeneous blue colour in the spinal cord and cauda equina was considered normal in our study, with the blue colour representing diffusion in the craniocaudal direction. Alteration in colour, thickness, and integrity, especially at the level of compression on T2W images, was considered significant.
Results: Out of 12 patients, 9 had signs of CSCM secondary to infective spondylodiskitis, 1 secondary to a disk protrusion, 1 secondary to a disk extrusion, and 1 secondary to the metastatic collapse of the vertebra.
In 8/12 patients with no spinal cord parenchymal signal alteration on T2W images, DTT revealed significant alteration in the colour-code both at and above the level of compression, signifying altered diffusion.
Conclusion: DTT is a more sensitive indicator of spinal cord compression than conventional MRI by revealing colour alterations, thinning and loss of integrity of spinal nerve fibre tracts, and providing an easy and fast tool to predict the need for surgical decompression.
Limitations: n/a
Ethics: n/a
Funding: No funding was received for this work.
RPS 1611-13
The role of the waist-to-hip ratio in brain networks: a connectometry study
Purpose: It is known from the literature that BMI influences cerebral networks. The purpose of this study is to evaluate the influence of the waist-to-hip ratio (W-H ratio) on brain networks by using the connectometry technique.
Methods: We recruited 30 healthy subjects (12 males, 18 female; age 25-80). The waist and hip circumferences of every patient were measured in order to calculate the W-H ratio and on the same day an MR examination was performed on a 3T scanner (Vantage Titan 3T, Canon) with a 32 channels head coil. The MR protocol included a 40 directions DW sequence for the connectometry analysis. The connectometry analysis was performed using a linear regression model to consider the effects of the W-H ratio, choosing three different T-score thresholds (T-threshold) values (1, 2, and 3). Results were considered statistically valid for a p-value adjusted for the false discovery rate (p-FDR) <0.05. The network topology analysis measured the influence of the W-H ratio on brain networks.
Results: The connectometry analysis identified several white matter bundles negatively correlated to the W-H score for T-threshold=2 and 3. Several properties of the network were influenced in the network topology analysis.
Conclusion: The W-H ratio influences brain networks. More studies are needed in order to fully understand these results.
Limitations: The small number of patients recruited and the DW parameters adopted, in particular, the low b-values.
Ethics: The study was approved by the local ethical committee. Informed consent was obtained.
Funding: No funding was received for this work.
RPS 1611-14
Neural correlates of insight and analytical anagram solving: fMRI study
Purpose: Insight is the sudden and unpredictable appearance of a problem's solution. The role of various brain structures in the generation of the insight phenomenon remains poorly understood. We aimed to study the neural correlates of the insight process during fMRI.
Methods: We performed fMRIs in 32 healthy subjects with a paradigm that involved solving anagrams. After giving an answer, the participants labelled their strategy as ?insight? or ?analytical?. The data was analysed using a GLM with predictors corresponding to different stimulus types and button presses. A random-effects analysis for the population was performed using a t-test over the individual contrast images.
Results: Areas activated during ?insight? problem-solving compared to rest included bilateral middle/superior frontal gyri, bilateral anterior insula, left frontal operculum, left precentral gyrus, left supplementary motor cortex, left superior parietal lobule, left putamen, left pallidum, right cerebellum, and bilateral inferior occipital gyri. Areas activated during ?analytical? problem-solving compared to rest included right superior frontal gyrus, bilateral anterior insula, left frontal operculum, left precentral gyrus, left supplementary motor cortex, bilateral superior parietal lobules, right cerebellum, left putamen, and bilateral inferior occipital gyri. Activation of the left precentral gyrus, left supplementary motor cortex, and right cerebellum during both insight and analytical solving can be attributed to right-hand movement for keystroke at the "solving" moment. The contrast between the ?insight? and ?analytical? problem-solving did not contain significant clusters at FWE<0.05.
Conclusion: Both analytical and insight solving are associated with the activation of multiple brain regions without significant difference in activation areas between strategies. Future studies using different paradigms and combined methods (fMRI, EEG, NIBS, etc.) are needed to elucidate neural correlates of insight.
Limitations: n/a
Ethics: Ethics committee approval obtained.
Funding: RFBR according to research project ? 18-00-01100 (?) (18-00-01078).
RPS 1611-15
Language lateralisation in tumour patients and healthy controls using functional MRI and diffusion tractography
Purpose: Our retrospective study investigates whether a correlation exists between functional language lateralisation using fMRI and structural lateralisation using diffusion data of language tracts in controls and tumour patients.
Methods: 15 controls and 61 patients were included and underwent structural, functional, and diffusion imaging on 3T MRI. Subjects performed verbal fluency and verb generation language fMRI tasks, and a laterality index (LI) was calculated using data from the cerebral hemisphere and the contralateral cerebellar hemisphere. The diffusion tracts included the long fibres of the arcuate fasciculus, anterior and posterior short fibres of the arcuate fasciculus, uncinate fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, and frontal aslant tract. An asymmetry index (AI) for each fibre pair was calculated using the tract volume derived from single tensor (ST) and spherical deconvolution (SD) diffusion data, as well as using the hindrance modulated orientational anisotropy (HMOA) derived from the SD method. A linear regression analysis between fMRI LI and DTI AI was performed.
Results: In all subjects, there was no significant correlation between fMRI LI and DTI AI for any of the tracts.
Conclusion: Our results do not justify replacing fMRI with tractography in the assessment of language lateralisation. The discordant results between ST- and SD-based asymmetry indices indicate that the structural lateralisation is less robust than the functional one.
Limitations: The predominately left-sided tumour distribution is due to the retrospective design, as included patients had all been selected clinically for presurgical assessment. The number of right-handed, left-handed, and ambidextrous subjects was not balanced. Disrupted or infiltrated fibres were excluded.
Ethics: The National Hospital for Neurology and Neurosurgery and Institute of Neurology Joint Research Ethics Committee approval was obtained.
Funding: No funding was received for this work.


Dorothee Auer (United Kingdom)

Eyal Lotan (Israel)

European Society of Radiology

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