Evaluation of the cognitive outcome after out-of-hospital cardiac arrest: The role of thalamus.

Cardiac arrest survivors develop a variety of neuropsychological impairments and neuroanatomical lesions. The goal of this study is to evaluate if brain voxel-based morphometry and lesional Magnetic Resonance Imaging (MRI) analyses performed in the acute phase of an Out-of-Hospital Cardiac Arrest (OHCA) can be sensitive enough to predict the persistence of neuropsychological disorders beyond 3 months. Survivors underwent a prospective brain MRI during the first month after an OHCA and performed neuropsychological assessments at 1 and 3 months. According to the second neuropsychological assessment, survivors were separated into two subgroups, a deficit subgroup with persistent memory, executive functions, attention and/or praxis disorders (n = 11) and a preserved subgroup, disorders free (n = 14). Brain vascular lesion images were investigated, and volumetric changes were compared with healthy controls. Correlations were discussed between brain MRI results, OHCA data and the second neuropsychological assessment. Analyses of acute ischemic lesions did not reveal significant differences between the two subgroups (p = .35), and correlations with cognitive impairments could not be assessed. voxel-based morphometry analyses revealed a global cerebral volume reduction for the two subgroups and a clear decrease of the right thalamic volume for the deficit subgroup. It was associated with a cognitive dysexecutive syndrome represented by four executive indexes according to the 'Groupe de Réflexion pour l'Evaluation des Fonctions EXécutives' criteria. The right thalamus atrophy seems to be more predictive than the vascular lesions and more specific than a global cerebral volume reduction of post-OHCA neuropsychological executive disorders.

White matter tracts lesions and decline of verbal fluency after deep brain stimulation in Parkinson's disease.

Decline of verbal fluency (VF) performance is one of the most systematically reported neuropsychological adverse effects after subthalamic nucleus deep brain stimulation (STN-DBS). It has been suggested that this worsening of VF may be related to a microlesion due to the electrode trajectories. We describe the disruption of surrounding white matter tracts following electrode implantation in Parkinson's disease (PD) patients with STN-DBS and assess whether damage of fiber pathways is associated with VF impairment after surgery. We retrospectively analyzed 48 PD patients undergoing bilateral STN DBS. The lesion mask along the electrode trajectory transformed into the MNI 152 coordinate system, was compared with white matter tract atlas in Tractotron software, which provides a probability and proportion of fibers disconnection. Combining tract- and atlas-based analysis reveals that the trajectory of the electrodes intersected successively with the frontal aslant tract, anterior segment of arcuate tract, the long segment of arcuate tract, the inferior longitudinal fasciculus, the superior longitudinal fasciculus, the anterior thalamic radiation, and the fronto striatal tract. We found no association between the proportion fiber disconnection and the severity of VF impairment 6 months after surgery. Our findings demonstrated that microstructural injury associated with electrode trajectories involved white matter bundles implicated in VF networks.

Diffusion tensor imaging in acute pyelonephritis in children.

BACKGROUND: Diffusion-weighted imaging plays a key role in the imaging of acute pyelonephritis by MRI. However the use of respiratory triggering is challenging and time-consuming in children. Diffusion tensor imaging without respiratory triggering might provide satisfying images of the moving kidneys. OBJECTIVE: To compare mean diffusivity diffusion tensor images obtained with free breathing with diffusion-weighted images obtained with respiratory triggering. MATERIALS AND METHODS: Thirty-one children with suspected acute pyelonephritis underwent axial diffusion tensor imaging acquisition with free breathing and axial and coronal diffusion-weighted imaging acquisitions with respiratory triggering. We compared image quality and detection of nephritis between the two sequences. RESULTS: Diffusion tensor imaging demonstrated agreement with diffusion-weighted imaging in all cases, with no difference in the detection of nephritis areas. The image quality was significantly better with diffusion tensor imaging (P<0.01). CONCLUSION: Diffusion tensor imaging could replace diffusion-weighted imaging for diagnosis of acute pyelonephritis.

Mirrored and rotated stimuli are not the same: A neuropsychological and lesion mapping study.

Agnosia for mirrored stimuli is a rare clinical deficit. Only eight patients have been reported in the literature so far and little is known about the neural substrates of this agnosia. Using a previously developed experimental test designed to assess this agnosia, namely the Mirror and Orientation Agnosia Test (MOAT), as well as voxel-lesion symptom mapping (VLSM), we tested the hypothesis that focal brain-injured patients with right parietal damage would be impaired in the discrimination between the canonical view of a visual object and its mirrored and rotated images. Thirty-four consecutively recruited patients with a stroke involving the right or left parietal lobe have been included: twenty patients (59%) had a deficit on at least one of the six conditions of the MOAT, fourteen patients (41%) had a deficit on the mirror condition, twelve patients (35%) had a deficit on at least one the four rotated conditions and one had a truly selective agnosia for mirrored stimuli. A lesion analysis showed that discrimination of mirrored stimuli was correlated to the mesial part of the posterior superior temporal gyrus and the lateral part of the inferior parietal lobule, while discrimination of rotated stimuli was correlated to the lateral part of the posterior superior temporal gyrus and the mesial part of the inferior parietal lobule, with only a small overlap between the two. These data suggest that the right visual 'dorsal' pathway is essential for accurate perception of mirrored and rotated stimuli, with a selective cognitive process and anatomical network underlying our ability to discriminate between mirrored images, different from the process of discriminating between rotated images.