Diffusion Tensor Imaging and Neuropsychologic Assessment in Aphasic Stroke

Nunnari, Domenica; Bramantı, Placido; Marıno, Silvia

doi:10.1016/j.jstrokecerebrovasdis.2014.07.047

Cited by 10 publications

(17 citation statements)

References 5 publications

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“…Another important variable that is often discounted is the extent of white matter tract damage, which measures of lesion size and location do not fully account for, but which may significantly impact response to tDCS. A large body of evidence suggests the critical role of white matter damage, especially along the arcuate fasciculus, in both the language deficits and course of recovery in PWA (Naeser et al, 1989 ; Marchina et al, 2011 ; Wang et al, 2013 ; Basilakos et al, 2014 ; Nunnari et al, 2014 ). The emergence of diffusion tensor imaging techniques has greatly simplified computation of the volume of damage within white matter tracts, or lesion load, which can be used to predict response to tDCS montages.…”

Section: Discussionmentioning

confidence: 99%

Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke

Shah-Basak

Norise²,

Garcia

et al. 2015

Front. Hum. Neurosci.

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While evidence suggests that transcranial direct current stimulation (tDCS) may facilitate language recovery in chronic post-stroke aphasia, individual variability in patient response to different patterns of stimulation remains largely unexplored. We sought to characterize this variability among chronic aphasic individuals, and to explore whether repeated stimulation with an individualized optimal montage could lead to persistent reduction of aphasia severity. In a two-phase study, we first stimulated patients with four active montages (left hemispheric anode or cathode; right hemispheric anode or cathode) and one sham montage (Phase 1). We examined changes in picture naming ability to address (1) variability in response to different montages among our patients, and (2) whether individual patients responded optimally to at least one montage. During Phase 2, subjects who responded in Phase 1 were randomized to receive either real-tDCS or to receive sham stimulation (10 days); patients who were randomized to receive sham stimulation first were then crossed over to receive real-tDCS (10 days). In both phases, 2 mA tDCS was administered for 20 min per real-tDCS sessions and patients performed a picture naming task during stimulation. Patients' language ability was re-tested after 2-weeks and 2-months following real and sham tDCS in Phase 2. In Phase 1, despite considerable individual variability, the greatest average improvement was observed after left-cathodal stimulation. Seven out of 12 subjects responded optimally to at least one montage as demonstrated by transient improvement in picture-naming. In Phase 2, aphasia severity improved at 2-weeks and 2-months following real-tDCS but not sham. Despite individual variability with respect to optimal tDCS approach, certain montages result in consistent transient improvement in persons with chronic post-stroke aphasia. This preliminary study supports the notion that individualized tDCS treatment may enhance aphasia recovery in a persistent manner.

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Section: Discussionmentioning

confidence: 99%

Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke

Shah-Basak

Norise²,

Garcia

et al. 2015

Front. Hum. Neurosci.

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“…Additionally, most of the previously mentioned studies evaluated global language ability, or a subtest, and thus cannot reflect comprehension ability. Moreover, previous work has focused on only a few tracts, due to the time-consuming nature of manual tractography ( 15 , 17 , 30 , 31 ), and diffusion characteristic variations along the trajectory of each fascicle have not been explored in subacute aphasic patients after stroke.…”

Section: Introductionmentioning

confidence: 99%

Multifunctional Roles of the Ventral Stream in Language Models: Advanced Segmental Quantification in Post-Stroke Aphasic Patients

et al. 2018

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In the dual-route language model, the dorsal pathway is known for sound-to-motor mapping, but the role of the ventral stream is controversial. With the goal of enhancing our understanding of language models, this study investigated the diffusion characteristics of candidate tracts in aphasic patients. We evaluated 14 subacute aphasic patients post-stroke and 11 healthy controls with language assessment and diffusion magnetic resonance imaging. Voxel-based lesion-symptom mapping found multiple linguistic associations for the ventral stream, while automated fiber quantification (AFQ) showed, via reduced fractional anisotropy (FA) and axial diffusivity with increased radial diffusivity (all corrected p < 0.05), that the integrity of both the left dorsal and ventral streams was compromised. The average diffusion metrics of each fascicle provided by AFQ also confirmed that voxels with significant FA-language correlations were located in the ventral tracts, including the left inferior fronto-occipital fascicle (IFOF) (comprehension: r = 0.839, p = 0.001; repetition: r = 0.845, p = 0.001; naming: r = 0.813, p = 0.002; aphasia quotient: r = 0.847, p = 0.001) and uncinate fascicle (naming: r = 0.948, p = 0.001). Furthermore, point-wise AFQ revealed that the segment of the left IFOF with the strongest correlations was its narrow stem. The temporal segment of the left inferior longitudinal fascicle was also found to correlate significantly with comprehension (r = 0.663, p = 0.03) and repetition (r = 0.742, p = 0.009). This preliminary study suggests that white matter integrity analysis of the ventral stream may have the potential to reveal aphasic severity and guide individualized rehabilitation. The left IFOF, specifically its narrow stem segment, associates with multiple aspects of language, indicating an important role in semantic processing and multimodal linguistic functions.

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“…Classically, the anatomical description of the basal ganglia circuitry has been based on axonal tracing in non-human primates and post-mortem fiber dissection in the human brain. However, in the last 20 years, Diffusion Tensor Imaging (DTI) tractography has been used as an anatomical “virtual dissector” for tracking in vivo and non-invasively neural connectivity in the human brain (Basser et al, 1994 ; Henderson, 2012 ; Nunnari et al, 2014 ), by measuring anisotropy diffusion of water molecules (Mori and Van Zijl, 2002 ).…”

Section: Introductionmentioning

confidence: 99%

A Connectomic Analysis of the Human Basal Ganglia Network

et al. 2017

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The current model of basal ganglia circuits has been introduced almost two decades ago and has settled the basis for our understanding of basal ganglia physiology and movement disorders. Although many questions are yet to be answered, several efforts have been recently made to shed new light on basal ganglia function. The traditional concept of “direct” and “indirect” pathways, obtained from axonal tracing studies in non-human primates and post-mortem fiber dissection in the human brain, still retains a remarkable appeal but is somehow obsolete. Therefore, a better comprehension of human structural basal ganglia connectivity in vivo, in humans, is of uttermost importance given the involvement of these deep brain structures in many motor and non-motor functions as well as in the pathophysiology of several movement disorders. By using diffusion magnetic resonance imaging and tractography, we have recently challenged the traditional model of basal ganglia network by showing the possible existence, in the human brain, of cortico-pallidal, cortico-nigral projections, which could be mono- or polysynaptic, and an extensive subcortical network connecting the cerebellum and basal ganglia. Herein, we aimed at reconstructing the basal ganglia connectome providing a quantitative connectivity analysis of the reconstructed pathways. The present findings reinforce the idea of an intricate, not yet unraveled, network involving the cerebral cortex, basal ganglia, and cerebellum. Our findings may pave the way for a more comprehensive and holistic pathophysiological model of basal ganglia circuits.

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Diffusion Tensor Imaging and Neuropsychologic Assessment in Aphasic Stroke

Cited by 10 publications

References 5 publications

Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke

Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke

Multifunctional Roles of the Ventral Stream in Language Models: Advanced Segmental Quantification in Post-Stroke Aphasic Patients

A Connectomic Analysis of the Human Basal Ganglia Network

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