Diffusion tensor imaging (DTI) allows in vivo structural brain mapping and detection of microstructural disruption of white matter (WM). One of the commonly used parameters for grading the anisotropic diffusivity in WM is fractional anisotropy (FA). FA value helps to quantify the directionality of the local tract bundle. Therefore, FA images are being used in voxelwise statistical analyses (VSA). The present study used Tract-Based Spatial Statistics (TBSS) of FA images across subjects, and computes the mean skeleton map to detect voxelwise knowledge of the tracts yielding to groupwise comparison. The skeleton image illustrates WM structure and shows any changes caused by brain damage. The microstructure of WM in thalamic stroke is investigated, and the VSA results of healthy control and thalamic stroke patients are reported. It has been shown that several skeleton regions were affected subject to the presence of thalamic stroke (FWE, p < 0.05). Furthermore the correlation of quantitative EEG (qEEG) scores and neurophysiological tests with the FA skeleton for the entire test group is also investigated. We compared measurements that are related to the same fibers across subjects, and discussed implications for VSA of WM in thalamic stroke cases, for the relationship between behavioral tests and FA skeletons, and for the correlation between the FA maps and qEEG scores.Results obtained through the regression analyses did not exceed the corrected statistical threshold values for multiple comparisons (uncorrected, p < 0.05). However, in the regression analysis of FA values and the theta band activity of EEG, cingulum bundle and corpus callosum were found to be related. These areas are parts of the Default Mode Network (DMN) where DMN is known to be involved in resting state EEG theta activity. The relation between the EEG alpha band power values and FA values of the skeleton was found to support the cortico-thalamocortical cycles for both subject groups. Further, the neurophysiological tests including Benton Face Recognition (BFR), Digit Span test (DST), Warrington Topographic Memory test (WTMT), California Verbal Learning test (CVLT) has been regressed with the FA skeleton maps for both subject groups. Our results corresponding to DST task were found to be similar with previously reported findings for working memory and episodic memory tasks. For the WTMT, FA values of the cingulum (right) that plays a role in memory process was found to be related with the behavioral responses. Splenium of corpus callosum was found to be correlated for both subject groups for the BFR.
Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis has been recently identified as a fulminant encephalopathy, presenting with a variety of symptoms including behavioral change, amnesia and seizures suggesting cortical gray matter involvement. A 42-year-old woman presented with acute-onset clinical and magnetic resonance imaging (MRI) findings indicating brainstem and diencephalon involvement. Her neuropsychological examination revealed mild frontal dysfunction with no memory impairment. Detailed diagnostic workup proved negative except for serum/cerebrospinal fluid (CSF) NMDAR-antibodies and increased activity in inguinal and pelvic lymph nodes on positron-emission tomography (PET) examination. The symptoms and MRI findings completely resolved following steroid treatment. A 38-year-old woman presented with migraine-type headache and episodes of forgetfulness. Her brain MRI and neuropsychological examination were normal and diagnostic workup was unremarkable. N-methyl-D-aspartate receptor antibodies were identified in her sera and her symptoms spontaneously resolved within few months. Our cases suggest that anti-NMDAR encephalitis might present with minimal cognitive impairment, no apparent cortical gray matter involvement, a mild clinical course and without the classical clinical features of the disease.
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