Showing papers on "Neural tract published in 2013"

Prediction of aphasia outcome using diffusion tensor tractography for arcuate fasciculus in stroke.

Abstract: BACKGROUND AND PURPOSE: The AF is an important neural tract in language function. We investigated aphasia outcome according to DTT findings for AF in the early stage of stroke. MATERIALS AND METHODS: Twenty-five consecutive patients with aphasia and stroke and 12 control subjects were recruited. The AQ of K-WAB was used for the assessment of aphasia in the early stage of stroke (10–30 days) and at approximately 6 months after onset. We classified the patients into 3 groups according to the severity of left AF injury: type A, the AF was not reconstructed; type B, the AF was disrupted; and type C, the AF was preserved around the lesion. RESULTS: When comparing AQ among AF types at early evaluation, the type C score (32.84 ± 18.05) was significantly higher than type A (3.60 ± 2.73) ( P P > .05). At late evaluation, the AQ values of types B (52.43 ± 25.75) and C (68.08 ± 15.76) were higher than that of type A (10.98 ± 3.90) ( P CONCLUSIONS: The aphasia outcome of the patients whose left AF could be reconstructed was better than that in patients whose left AF could not be reconstructed, irrespective of its integrity. We believe that evaluation of the left AF by using DTT in the early stage of stroke could be helpful in predicting aphasia outcome in patients with stroke.

A role for the ventral pallidum in context-induced and primed reinstatement of alcohol seeking.

Abstract: The ventral pallidum (VP) is a major target of projections from the nucleus accumbens, and has been implicated in the reinstatement of psychostimulant seeking as part of a cortical-striatal-pallidal 'final common pathway' for relapse. Here, we studied the role of the VP in context-induced and primed reinstatement of alcoholic beer seeking, using a combination of microinjections and tract tracing studies. In experiment 1, rats were trained to respond to alcoholic beer in one context (A), and then extinguished in a second context (B), prior to testing for reinstatement (ABA renewal) and extinction (ABB). VP microinjection of the μ-opioid receptor (MOR) antagonist CTAP prevented reinstatement. In experiment 2, VP microinjection of CTAP also prevented the primed reinstatement of alcoholic beer seeking after rats were trained, extinguished, and tested in the same context. In experiment 3, we employed retrograde neural tract tracing together with c-Fos immunohistochemistry to identify the VP afferents recruited during context-induced reinstatement of alcoholic beer seeking. There was evidence for the recruitment of accumbens core→VP, basolateral amygdala→VP and paraventricular thalamus→VP pathways during context-induced reinstatement. These results indicate that the VP MORs are critical for context-induced reinstatement, and that the VP receives inputs from a number of regions known to be important in reinstatement of drug seeking.

Tractography-guided stimulation of somatosensory fibers for thalamic pain relief

Abstract: Background: The spinothalamocortical tract (STC) is seen as a neural tract responsible for or involved in the generation or transmission of thalamic pain. Either the thalamus itself or the posterior limb of the internal capsule (PLIC) are targets for deep brain stimulation (DBS) in patients with thalamic pain, but due to its low contrast, conventional MRI cannot visualize the STC directly. Objectives: To show the feasibility of integrating diffusion tensor imaging-based tractography into the stereotactic treatment planning for identification of an object-oriented lead trajectory that allows STC-DBS with multiple electrode contacts. Methods: Diffusion tensor imaging was performed in 4 patients with thalamic pain. The STC was modeled and integrated into the stereotactic treatment planning for DBS. DBS-lead implantation was done according to trajectory planning along the modeled STC at the level of the PLIC. Results: After implantation, electrode stimulation was possible over a length of more than 20 mm with a tractography-based trajectory along the PLIC part of the STC. After a follow-up of 12 months, pain relief of more than 40% was achieved in 3 of 4 patients with rating on a visual analogue scale. In 1 patient, stimulation failed to reach any long-lasting positive effects. Conclusions: Integrating tractography data into stereotactic planning of DBS in thalamic pain is technically feasible. It can be used to identify a lead trajectory that allows for multiple contact stimulation along the STC at the level of the PLIC. Due to long-lasting positive stimulation effect, tractography-guided stimulation of sensory fibers seems to be beneficial for thalamic pain relief.

Diffusion Tensor Imaging Studies on Arcuate Fasciculus in Stroke Patients: A Review

Abstract: Aphasia is one of the most common and devastating sequelae of stroke. The arcuate fasciculus (AF), an important neural tract for language function, connects Broca's and Wernicke's areas. In this review article, previous diffusion tensor imaging (DTI) studies on the AF in stroke patients were reviewed with regard to the usefulness for diagnosis (seven studies), prediction of prognosis (two studies), and recovery of aphasia (three studies). Although scant studies on this topic have been conducted in stroke patients, DTI for the AF appears to provide useful information on the presence or severity of injury of the AF, prognosis prediction of aphasia, and recovery mechanisms of aphasia in stroke patients. Therefore, further DTI studies on these topics should be encouraged, especially studies on prognosis prediction and recovery mechanisms of aphasia. In addition, research on other neural tracts known to be involved in aphasia as well as the AF in both hemispheres should be encouraged.

Neural reorganization following bilateral injury of the fornix crus in a patient with traumatic brain injury.

Abstract: Objective: We report on a patient who appeared to demonstrate neural reorganization after head trauma resulting in bilateral injury of the fornix crus. Case report: A 58-year-old male patient and 8 control subjects were recruited. The patient had undergone head trauma as the result of a car accident and had lost consciousness for 30 min. Brain magnetic resonance imaging, performed 3 years after the head trauma, showed no evidence of abnormality. Results: Discontinuation of both crus in the proximal region was observed on diffusion tensor tractography of the fornix. In the right fornix, an abnormal neural tract originating from the right crus passed through the splenium of the corpus callosum to connect with the right inferior longitudinal fasciculus. By contrast, in the left fornix, another abnormal neural tract originating from the left column passed through the left inferior longitudinal fasciculus and the splenium of the corpus callosum. None of these abnormal neural tracts was observed in normal subjects. Conclusion: We presume that the abnormal neural tracts of the fornix observed in this patient were the result of neural reorganization triggered by bilateral injury of the fornix crus. The results of this study suggest a mechanism for recovery of the injured fornix following head trauma.

Diagnosis, Histopathologic and Genetic Classification of Uveal Melanoma

Abstract: Uveal melanoma (UM) is the most common cause of primary eye cancer in the western world During embryogenesis neural crest cells migrate to the neural tract where they devel‐ op into melanocytes Melanomas of the uvea are derived from these melanocytes UM may arise in the iris (5%), ciliary body (23%) or choroid (72%) Choroidal melanomas are the most common and usually display a discoid, dome-shaped or mushroom shaped growth pattern Approximately 80% of the primary intraocular tumours are diagnosed as UM in patients above the age of 20 years, with a mean age of 60 years (Singh & Topham, 2003) Despite a shift towards more conservative eye treatments, survival has not improved during 1973 to 2008 (Singh et al, 2011) Growth of the primary tumour is related with histopathological fea‐ tures, as well as the genetic changes within these tumours In this chapter we will not dis‐ cuss iris melanoma, as this shows a different clinical and genetic behaviour, compared to ciliary body and choroidal melanoma The clinical features, histopathological profile and ge‐ netic alterations of UM, as well as therapeutic options for primary tumours and metastases will be discussed

Neural Tract Injuries by Penetration of Foreign Body: a Diffusion Tensor Tractography Study

Abstract: We presented with a patient who showed injury of the cingulum and fornix by penetration of a foreign body into the brain on diffusion tensor tractography (DTT). A 63-year-old man suffered a brain injury by a part of a power saw blade that was suddenly detached from a power saw during work. A part of the power saw blade penetrated his right frontal skull and advanced to the right posterior horn of the lateral ventricle. This penetration caused traumatic intracerebral hemorrhage in the right frontal lobe and intraventricular hemorrhage in the lateral ventricle. He underwent craniotomy and removal of intracranial foreign bodies (bony pieces and saw blade). The patient’s Memory Assessment Scale scores were 74 (4%ile) for global memory, 78 (7%ile) for verbal memory, and 80 (9%ile) for visual memory. DTTs showed disruptions in the anterior portion of the fornical body, right fornical crus, the anterior portion of the right cingulum, and the middle portion of the left cingulum, compared to the control. It seems that the sustained memory impairment of this patient might be related to injury of the cingulum and fornix.

Magnetic resonance microscopy of Aplysia neurons : studying neurotransmitter-modulated transport and response to stress

Abstract: Recent progress in magnetic resonance imaging (MRI) has opened the way for micron-scale resolution, and thus for imaging biological cells. In this thesis work, we performed magnetic resonance microscopy (MRM) on the nervous system of Aplysia californica, a model particularly suited due to its simplicity and to its very large neuronal cell bodies, in the aim of studying cellular-scale processes with various MR contrasts. Experiments were performed on a 17.2 Tesla horizontal magnet, at resolutions down to 25 µm isotropic. Initial work consisted in conceiving and building radiofrequency microcoils adapted to the size of single neurons and ganglia. The first major part of the project consisted in using the manganese ion (Mn2+) as neural tract tracer in the buccal ganglia of Aplysia. Manganese is an MR contrast agent that enters neurons via voltage-gated calcium channels. We performed the mapping of axonal projections from motor neurons into the peripheral nerves of the buccal ganglia. We also confirmed the existence of active Mn2+ transport inside the neural network upon activation with the neurotransmitter dopamine. In the second major part of the project, we tested the potential of two diffusion MRI sequences for microscopy. On the one hand, we explored a very original mechanism for diffusion weighting, DESIRE (Diffusion Enhancement of SIgnal and REsolution), particularly suited for small samples. The two-dimensional DESIRE sequence was implemented and successfully tested on phantoms. The measured enhancement was consistent with theoretical predictions. Using this sequence to produce diffusion weighted images with an unprecedented contrast in biological tissue remains a challenge. On the other hand, a more “standard” sequence was implemented to measure the apparent diffusion coefficient (ADC) in nervous tissue with MRM. This sequence was a three-dimensional DP-FISP (Diffusion Prepared Fast Imaging with Steady-state free Precession), which met criteria for high resolution in a short acquisition time, with minimal artifacts. Using this sequence, we studied the changes in water ADC at different scales in the nervous system, triggered by cellular challenges. The challenges were hypotonic shock or exposure to ouabain. ADC measurements were performed on single isolated neuronal bodies and on ganglia tissue, before and after challenge. Both types of stress produced an ADC increase inside the cell and an ADC decrease at tissue level. The results favor the hypothesis that the increase in membrane surface area associated with cell swelling is responsible for the decrease of water ADC in tissue, typically measured in ischemia or other conditions associated with cell swelling.

Recovering local neural tract directions and reconstructing neural pathways in high angular resolution diffusion mri

Abstract: OF DISSERTATION RECOVERING LOCAL NEURAL TRACT DIRECTIONS AND RECONSTRUCTING NEURAL PATHWAYS IN HIGH ANGULAR RESOLUTION DIFFUSION MRI Magnetic resonance imaging (MRI) is an imaging technique to visualize internal structures of the body. Diffusion MRI is an MRI modality that measures overall diffusion effect of molecules in vivo and non-invasively. Diffusion tensor imaging (DTI) is an extended technique of diffusion MRI. The major application of DTI is to measure the location, orientation and anisotropy of fiber tracts in white matter. It enables non-invasive investigation of major neural pathways of human brain, namely tractography. As spatial resolution of MRI is limited, it is possible that there are multiple fiber bundles within the same voxel. However, diffusion tensor model is only capable of resolving a single direction. The goal of this dissertation is to investigate complex anatomical structures using high angular resolution diffusion imaging (HARDI) data without any assumption on the parameters. The dissertation starts with a study of the noise distribution of truncated MRI data. The noise is often not an issue in diffusion tensor model. However, in HARDI studies, with many more gradient directions being scanned, the number of repetitions of each gradient direction is often small to restrict total acquisition time, making signal-to-noise ratio (SNR) lower. Fitting complex diffusion models to data with reduced SNR is a major interest of this study. We focus on fitting diffusion models to data using maximum likelihood estimation (MLE) method, in which the noise distribution is used to maximize the likelihood. In addition to the parameters being estimated, we use likelihood values for model selection when multiple models are fit to the same data. The advantage of carrying out model selection after fitting the models is that both the quality of data and the quality of fitting results are taken into account. When it comes to tractography, we extend streamline method by using covariance of the estimated parameters to generate probabilistic tracts according to the uncertainty of local tract orientations.