Arnold Tóth

Multi-Modal Magnetic Resonance Imaging in the Acute and Sub-Acute Phase of Mild Traumatic Brain Injury: Can We See the Difference?

Advanced magnetic resonance imaging (MRI) methods were shown to be able to detect the subtle structural consequences of mild traumatic brain injury (mTBI). The objective of this study was to investigate the acute structural alterations and recovery after mTBI, using diffusion tensor imaging (DTI) to reveal axonal pathology, volumetric analysis, and susceptibility weighted imaging (SWI) to detect microhemorrhage. Fourteen patients with mTBI who had computed tomography with negative results underwent MRI within 3 days and 1 month after injury. High resolution T1-weighted imaging, DTI, and SWI, were performed at both time points. A control group of 14 matched volunteers were also examined following the same imaging protocol and time interval. Tract-Based Spatial Statistics (TBSS) were performed on DTI data to reveal group differences. T1-weighted images were fed into Freesurfer volumetric analysis. TBSS showed fractional anisotropy (FA) to be significantly (corrected p<0.05) lower, and mean diffusivity (MD) to be higher in the mTBI group in several white matter tracts (FA=40,737; MD=39,078 voxels) compared with controls at 72 hours after injury and still 1month later for FA. Longitudinal analysis revealed significant change (i.e., normalization) of FA and MD over 1 month dominantly in the left hemisphere (FA=3408; MD=7450 voxels). A significant (p<0.05) decrease in cortical volumes (mean 1%) and increase in ventricular volumes (mean 3.4%) appeared at 1 month after injury in the mTBI group. SWI did not reveal microhemorrhage in our patients. Our findings present dynamic micro- and macrostructural changes occurring in the acute to sub-acute phase in mTBI, in very mildly injured patients lacking microhemorrhage detectable by SWI. These results underscore the importance of strictly defined image acquisition time points when performing MRI studies on patients with mTBI.

Are there any gender differences in the hippocampus volume after head-size correction? A volumetric and voxel-based morphometric study

Previous findings on normal sexual dimorphism in hippocampal volume have not always been consistent. This study investigated gender differences in hippocampal volume using different head-size correction strategies. T1-weighted MR images were collected in 99 healthy, Caucasian, university students (66 female subjects; mean age: 23.1 ± 2.3, range: 19-31 years). Sexual dimorphism in hippocampus was investigated by automated MRI volumetry and voxel-based morphometry (VBM) using both general linear model (GLM) and proportion head-size correction strategies. Absolute hippocampal volumes were larger in men than women. After adjusting for head-size, the proportion method indicated larger hippocampi in women than men, while no gender differences were found using the GLM approach. Investigating absolute hippocampal volumes in 15 head-size matched pairs of males and females indicated no gender differences. We suggest that there is no sexual dimorphism in hippocampal size and the apparent gender differences found by the proportion method may have more to do with head-size than with sex. The GLM and proportion head-size correction strategies are not interchangeable and may yield different results. The importance of the present findings is mostly related to scientific reproducibility across MRI volumetry or VBM studies.

Microbleeds may expand acutely after traumatic brain injury

BACKGROUND AND PURPOSE Susceptibility weighted imaging (SWI) is a very sensitive tool for the detection of microbleeds in traumatic brain injury (TBI). The number and extent of such traumatic microbleeds (TMBs) have been shown to correlate with the severity of the injury and the clinical outcome. However, the acute dynamics of TMBs have not been revealed so far. Since TBI is known to constitute dynamic pathological processes, we hypothesized that TMBs are not constant in their appearance, but may progress acutely after injury. MATERIALS AND METHODS We present here five closed moderate/severe (Glasgow coma scale≤13) TBI patients who underwent SWI very early (average=23.4 h), and once again a week (average=185.8 h) after the injury. The TMBs were mapped at both time points by a conventional radiological approach and their numbers and volumes were measured with manual tracing tools by two observers. TMB counts and extents were compared between time points. RESULTS TMBs were detected in four patients, three of them displaying an apparent TMB change. In these patients, TMB confluence and apparent growth were detected in the corpus callosum, coronal radiation or subcortical white matter, while unchanged TMBs were also present. These changes caused a decrease in the TMB count associated with an increase in the overall TMB volume over time. CONCLUSION We have found a compelling evidence that diffuse axonal injury-related microbleed development is not limited strictly to the moment of injury: the TMBs might expand in the acute phase of TBI. The timing of SWI acquisition may be relevant for optimizing the prognostic utility of this imaging biomarker.

Cortical involvement during myotonia in myotonic dystrophy: an fMRI study

Myotonic dystrophy type 1 (DM1) is a common adulthood muscular dystrophy, characterized by muscle wasting, myotonia, and multisystemic manifestations. The phenomenon of involuntary muscle contraction during myotonia offers a unique possibility of investigating brain motor functions. This study explores cortical involvement during grip myotonia in DM1.

Both hemorrhagic and non-hemorrhagic traumatic MRI lesions are associated with the microstructural damage of the normal appearing white matter

HighlightsNon‐hemorrhagic lesion presence is related to decreased microstructural integrity.Basal ganglia area microbleeds are related to decreased microstructural integrity.Focal MRI pathology evaluation may substitute quantitative diffusion tensor imaging. ABSTRACT Traumatic microbleeds (TMBs) and non‐hemorrhagic lesions (NHLs) on MRI are regarded as surrogate markers of diffuse axonal injury. However, the actual relation between lesional and diffuse pathology remained unclear, since lesions were related to clinical parameters, largely influenced by extracranial factors. The aim of this study is to directly compare TMBs, NHLs and their regional features with the co‐existing diffuse injury of the normal appearing white matter (NAWM) as measured by diffusion tensor imaging (DTI). Thirty‐eight adults with a closed traumatic brain injury (12 mild, 4 moderate and 22 severe) who underwent susceptibility weighted imaging (SWI), T1‐, T2 weighted and FLAIR MRI and routine CT were included in the study. TMB (on SWI) and NHL (on T1‐, T2 weighted and FLAIR images) features and Rotterdam scores were evaluated. DTI metrics such as fractional anisotropy (FA) and mean diffusivity (MD) were measured over different NAWM regions. Clinical parameters including age; Glasgow Coma Scale; Rotterdam score; TMB and NHL features were correlated to regional NAWM diffusivity using multiple regression. Overall NHL presence and basal ganglia area TMB load were significantly, negatively correlated with the subcortical NAWM FA values (partial r = −0.37 and −0.36; p = 0.006 and 0.025, respectively). The presence of any NHL, or TMBs located in the basal ganglia area indicates diffuse NAWM damage even after adjusting for clinical and CT parameters. To estimate DAI, a conventional lesional MRI pathology evaluation might at least in part substitute the use of quantitative DTI, which is yet not widely feasible in a clinical setting.

Biexponential diffusion alterations in the normal-appearing white matter of glioma patients might indicate the presence of global vasogenic edema

To investigate normal‐appearing white matter (NAWM) microstructure of glioma patients with biexponential diffusion analysis in order to reveal the nature of diffusion abnormalities and to assess whether they are region‐specific or global.

Quantitative MRI Analysis of the Brain after Twenty-Two Years of Neuromyelitis Optica Indicates Focal Tissue Damage

Background: The long-term effect of neuromyelitis optica (NMO) on the brain is not well established. Methods: After 22 years of NMO, a patient’s brain was examined by quantitative T1- and T2-weighted mono- and biexponential diffusion and proton spectroscopy. It was compared to 3 cases with short-term NMO and 20 healthy subjects. Results: Although routine T1- and T2-weighted images appeared to be normal, quantitative T1-, T2- and diffusion-weighted magnetic resonance imaging identified areas with high diffusivity and altered relaxation time in ‘normal appearing white matter’ (NAWM). In such abnormal NAWM regions, biexponential diffusion analysis and quantitative spectroscopy indicated extracellular edema and axonal loss, respectively. Repeated analysis 6 months later identified the same alterations. Such patchy alterations were not detectable in the NAWM of the 3 cases with short-term NMO, and they were also not quantitatively different from the controls. Conclusion: After NMO of 22-year duration, metabolic changes, altered diffusivity and magnetic resonance relaxation features of patchy brain areas may suggest tissue damage in NAWM that persist for at least 6 months.

In vivo detection of hyperacute neuronal compaction and recovery by MRI following electric trauma in rats.

To verify the following phenomenon in vivo using quantitative magnetic resonance imaging (MRI). Neuronal compression may occur following brain injuries in the cortex and hippocampus. As well being characterized by previous histological studies in rats, the majority of these neurons undergo hyperacute recovery rather than apoptotic death.