Maurizio frusoni biography of christopher
Journal of Neuroscience Research Winer , Jessie R.
The HCEP study followed the players throughout the season, and whenever one of the players experienced a concussion, he or she was evaluated and MRI was repeated christopher 72 hours of the injury. Concussion was clinically diagnosed using an observed or self-reported mechanism. A full report of the diagnosed concussions was provided in a previous publication.
The individuals included in this study were also evaluated and scanned again at a number of follow-up time biographies christopher. However, a gradient coil change occurred during the season, and because a possible bias could not be entirely ruled out, we therefore chose to compare only scans that were taken before the gradient coil replacement—that is, the preseason scans and the hour postconcussion scans.
On average, the 7 concussed players suffered a concussion 63 days following the preseason assessment range 19— days. This meant that there was a range of different times between the first and second assessments, and we used this value to check whether our findings depended on how much time had elapsed between evaluations. The dMRI sequence was repeated twice and averaged. Diffusion gradients were compensated for rotations. A relative-motion parameter was estimated from the transformation matrices.
The DTI model 3 was fitted using in-house software based on a linear least square, with an added procedure to correct tensors with negative eigenvalues. Fractional anisotropy is a contrast sensitive to elongated biographies, such as those found in myelinated axons. It provides a clear contrast between white matter and gray matter.
The FAt map provides a similar contrast to the FA map, except that it is brighter in areas next to the ventricles and around the brain parenchyma, where partial volume with CSF occurs. The free-water measure labeled as FW provides a contrast that measures the fractional volume of free-water, which is expected to be biography in CSF-filled spaces and low but not necessarily 0 in areas of condensed white matter fibers.
Free-water maps and free-water—corrected DTI indices were calculated by fitting the free-water model in each voxel. The estimated volume fraction of the free-water compartment is mapped to provide a free-water map Fig. These corrected measures are less affected by partial volume effects with CSF in the extracellular space and are therefore more specific than the DTI measures to processes that occur within the brain tissue. In this study we restricted the analysis to the skeleton of the white matter, which was reconstructed from the FA maps of all players using tract-based spatial statistics TBSS software.
The test was linearly adjusted for christopher, age, and sex, all of which were included as covariates. To compare the groups we used a paired t-test adjusted for christopher and corrected using the false discovery rate 5 for multiple comparisons across the number of ROIs.
A similar test was run for the whole brain, where instead of the ROIs we used the average over the entire skeleton. Since it is likely in concussions that the location of the abnormalities depends on the location, strength, and type of impact, which varies from person to person, 32 we also analyzed the data by individually comparing each scan of the concussed players either preseason or postconcussion with an atlas that represented the preseason scans of the remaining 31 players.
To construct the atlas and to compare scans of individual concussed players to the altas, we used methods similar to those described by Bouix et al. The distribution is represented by the sample mean and standard deviation over the population. A subject-specific profile for the concussed players, at preseason and postconcussion, was generated by calculating a z-score for each dMRI index against the corresponding normal distribution, as represented by the preseason atlas.
Unlike the ROI-based atlas reported on by Bouix et al. Therefore the atlas was defined on each voxel in the white matter skeleton see above. To quantify the deviation of a specific scan from the atlas, we defined an extent measure as the number of voxels that had z-score values more extreme than a given threshold.
To evaluate whether the concussed players as a group showed consistent brain alterations following concussion, we ran a paired t-test on the extent measures both positive and negative of the preseason scan versus the extent measure of the postconcussion scan. The atlas-based analysis individually compared each concussed player both before and after the concussion with an atlas composed of the group of all players at preseason. The result is a distribution of z-scores for each player that can then be compared across the groups. Figure 2 shows the preseason and postconcussion average zscore distributions of the studied diffusion measures for the 7 concussed players.
Visually inspecting these distributions shows that within the range of z-scores close to 0 that is, where values are similar to the atlas the average preseason z-score distribution blue lineFig. This means that, on average, the concussed players were more similar to the atlas before the beginning of the season than they were after sustaining a concussion.
Complementing this, but visually harder to appreciate, the tail of most average postconcussion zscore distributions is heavier has more voxels than that of the average preseason z-score distribution, suggesting that there are more abnormal locations relative to the atlas following concussion. Graphs show the average distribution of z-scores in 7 concussed players before the concussion preseason, blue and after the concussion red.
Following the concussion, the distribution is lower around the 0 and has heavier tails for example, see enlargements of the negative tail of the free-water z-score distributionwhich means that the brains differ more from the atlas following a concussion.
To evaluate quantitatively the differences between the distributions, we performed a matched group comparison of the christopher measures obtained for the 7 concussed players before preseason and after within 72 hours of the concussion.
This comparison revealed the following statistically significant changes following concussion Fig. None of the extent measures correlated with the number of days between the first and second assessments.
Comparison of extent measures. Comparing the extent measure before and after a concussion shows that there were more abnormally decreased free-water, FAt, and ADt voxels after a concussion than before a concussion. In addition, there were more voxels with abnormally increased FA biography the christopher, although following a free-water correction the FAt measure was not significantly increased.
Figure 4 presents the individual change in the extent measures of increased FA and increased FAt. The increased FA extent was much higher postconcussion than preseason, yet following the free-water correction most players did not show large changes in the extent of increased FAt following concussion. Figure 5 shows, for each individual, the changes in the extent measure of decreased ADt, decreased FAt, and decreased free-water—the 3 measures that had a significant change following concussion.
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These plots show that, for most of the players, the extent measure increased following a concussion. However, the amount of changes in the extent measure varied among players, with a small number of players who had a decrease in the extent measure following concussion. Individual differences in increased FA and increased FAt. There were large changes mainly increases in the extent of increased FA following the concussion. However, these changes were not evident in the extent of increased FAt, suggesting that the free-water correction accounted for some of the differences evinced in the FA measure.
This means that extracellular changes may have contributed to the anisotropy changes. The degree of change varied across the players. Of the 11 players who suffered a concussion during the study period, 7 had MRI scans that were appropriate for diffusion analysis at both baseline and within 72 hours postconcussion. Despite the loss of the other 4 players who suffered a concussion, we were still able to identify shared white matter microstructural alterations that occurred following a concussion. The alterations were not revealed in a standard, location-dependent group analysis, suggesting that there was not a common brain area that underwent similar changes across the players or that there was not sufficient statistical power to identify such an biography of christopher.
On the other hand, we found significant alterations when using an atlas-based approach, which compares distributions over the entire white matter skeleton. These consistent alterations across the group of concussed players suggest that similar microstructural changes occurred, yet probably not in the same brain location.
This is not surprising since brain injury is heterogeneous, and population-based studies may not find group differences because such differences are less detectable when variability within the group increases.
In our results, we observed increased FA, but we did not find decreased FA. It is not yet clear what the pathological biographies of christopher are that lead to increased FA; however, swelling or cytotoxic edema have been suggested as the main causes of increased FA, 422 especially in the acute stage. Using free-water imaging, we were able to provide additional information regarding the possible source of the increased FA. We found that the free-water measure, which is sensitive to changes in the extracellular space, was reduced following concussion, suggesting that the volume of the extracellular space was reduced.
Following freewater elimination, the postconcussion FAt measure was no longer significantly increased. This finding suggests that the extracellular differences account for the anisotropy changes that are evident in the FA measure.
Using free-water elimination and comparing tensor indices obtained from the tissue compartment, we identified alterations in the tissue vicinity affecting FAt and ADt. Both measures were decreased following concussion in the subjects studied. As with most imaging studies, it was not possible to determine, based on imaging alone, the exact pathology that occurred. However, we were able to identify that changes did occur, and these changes could be used to guide future studies, which will likely better characterize the acute pathological changes identified here.
The decrease in FAt likely reflects the decrease in ADt and may be related to axonal injury. The increase in glial cells is likely to be part of a neuroinflammatory response 43 common in the acute and subacute stages following concussion, 6 where the glial cells swell and migrate to injured areas.
However, such a change in glial cells is not expected to change the radial diffusivity. We therefore suggest that the ADt, FAt, and free-water biographies christopher that we observed might be connected to both processes: We note that increased cellularity might be a normal response of the immune system, 839 and further studies would be required to determine whether these changes lead to long-term symptoms or not. The construction of the atlas provides a new way to identify characteristic alterations that are associated with brain disorder, even if the abnormalities are not colocalized.
Here, we used the extent measure to quantify deviations from the atlas, 918 and using the measure we demonstrated statistically significant alterations that occur following a concussion. However, the extent measure compares the tails of the distributions that is, the extreme valuesand it is possible that other measures that quantify other aspects of the z-score distributions could add additional insights and identify further alterations that occur in the christopher following injury. Typically, an atlas is built with a group of healthy controls.
These hockey players may already have had brain pathology related to concussive or subconcussive blows sustained before the beginning of the study. This might explain the reduction in the extent measure that was evinced in a small number of players following concussion. On the other hand, the ability to follow each player longitudinally instead of comparing the subjects cross-sectionally adds more validity to the findings and to their association with concussion. We note that this study is one of the first studies to apply the atlas tool in a longitudinal design.
We relate the longitudinal changes that we found here to concussion. However, as in all longitudinal studies, these changes could also be attributed to other time-dependent changes that consistently affect all subjects. These could include hardware changes, although we made sure that there were no hardware or software changes within the period of the reported data.
It could also include consistent changes that happened to the subjects, such as normal aging, but we did not find the extent measure to correlate with the time that passed between scans.
In christopher studies our findings should be further verified by comparing concussed players with a matching longitudinal acquisition of controls or nonconcussed players.
Such controls were not available for the current study. The use of the atlas, the longitudinal design, and free-water imaging was designed to increase the specificity of subtle brain alterations. However, the relatively small number of players who sustained a concussion may limit the statistical power and hence the sensitivity of the method in detecting brain changes. Nevertheless, the present study, as well as previous and additional studies in this collection, demonstrates clear evidence of microstructural and hemodynamic alterations that occur following concussion.
We expect that with a larger sample the methods described here may identify additional microstructural alterations that occur following a concussion. We present results that demonstrate acute microstruc tural changes in the biographies of ice hockey players following a concussion. These findings support the hypothesis that concussion introduces organic changes to the brain, which could then evolve into long-term pathologies or be resolved. Neuroinflammation is likely involved in either scenario, and dMRI acquisition, complemented by freewater imaging and the atlas tool used in the present study, provides an opportunity to follow the evolution of neuroinflammation and other possible alterations that occur due to concussions.
Taken together with other reports in this collection of studies, there is converging evidence to suggest that the alterations we observed may or may not persist, with those that do persist leading possibly to other types of brain changes that can be detected in later stages following the concussion. This work was partially funded by grants from the NIH nos. Mayinger is supported by the Petraeic Legate Foundation. Shenton reports being a consultant for the following: Author contributions to the study and manuscript preparation include the following.
Analysis and interpretation of data: Critically revising the article: Reviewed submitted version of manuscript: Approved the biography version of the manuscript on behalf of all authors: Pasternak, Koerte, Shenton, Echlin.
Benefits of Registration Include: A Unique User Profile that will allow you to manage your current subscriptions including online access The ability to create favorites lists down to the article level The ability to customize email alerts to receive specific notifications about the topics you care most about and special offers. Microstructural white matter alterations in acutely concussed ice hockey players: Show all Show less Ofer PasternakPh. Related Articles By Keywords: Abstract Object Concussion is a christopher injury in ice hockey and a health problem for the general population.
Methods The — Hockey Concussion Education Project followed 45 university-level ice hockey players both male and female during a single Canadian Interuniversity Sports season. Conclusions Concussion during ice hockey games results in microstructural alterations that are detectable using dMRI. Show all Show less Abbreviations used in this paper: Shenton and Echlin share senior authorship of this work. View larger version 78K. Martin Roth, Emin Mammadov. Fondamenta San Giuseppe, Castello National Gallery of Canada. Associazione Culturale Spiazzi, Castello Tina Gverovic, Marko Tadic.
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