Poster No:
2152
Submission Type:
Abstract Submission
Authors:
Maggie Baird1, Marc Seal2, Richard Beare2, Joseph Yang2, Jacqueline Anderson3
Institutions:
1The University of Melbourne, Parkville, Victoria, 2Murdoch Children's Research Institute, Melbourne, VIC, 3The University of Melbourne, Melbourne, VIC
First Author:
Maggie Baird
The University of Melbourne
Parkville, Victoria
Co-Author(s):
Marc Seal
Murdoch Children's Research Institute
Melbourne, VIC
Richard Beare
Murdoch Children's Research Institute
Melbourne, VIC
Joseph Yang
Murdoch Children's Research Institute
Melbourne, VIC
Introduction:
Evidence points to the vulnerability of the thalamus in mild traumatic brain injury (mTBI), due to its anatomical position at the brains' centre of mass and abundant cortical connectivity profile. Few studies have systematically investigated the possibility of structural change in the thalamus, nor have they adequately assessed its constituent subnuclei. The treatment of the thalamus as a unitary structure may mask subtle structural changes, which is problematic considering the variable functional contributions of thalamic subnuclei to cognitive, sensory, and motoric functions, Therefore, we aimed to investigate whole and thalamic subnuclei volume following mTBI, using a joint structural MRI (sMRI) and diffusion MRI (dMRI) Bayesian segmentation algorithm to segment the thalamus into subregions.
Methods:
39 mTBI patients and 29 trauma control (TC) patients aged 18 – 60 were recruited as inpatients. Participants were classified into the mTBI group if they fulfilled the World Health Organisation criteria for definition of mTBI, and into the TC group if they sustained a traumatic injury in the absence of a head strike. Participants completed an MRI neuroimaging protocol including both sMRI (MPRAGE) and dMRI (b = 0, b = 1000, b = 3000s/mm2) sequences at 6 – 10 weeks (m = 57 days, sd = 11) following injury. Lateralised whole and regional thalamic volumes were estimated using a Bayesian joint structural and diffusion segmentation method, yielding 25 labels per hemisphere which were merged to create nuclei groups. Bayesian linear models were fitted, with age and estimated intracranial volume (ICV) as covariates. Firstly, the median and 95%Highest Density Interval (HDI) are reported. There is a 95% probability the effect is within this confidence interval. Additionally, three sequential probabilities are reported: of direction, of significance (effect is of sufficient size to be considered non-negligible), and of being large. The thresholds for significant and large effects are 0.05*SDy and 0.3*SDy respectively.
Results:
Analysis revealed some evidence for greater whole thalamic volume and thalamic subnuclei between the groups, although the magnitude of effect varied. Briefly, the effect of Group [TC] on right whole thalamus volume (median = -0.34, 95% CI [-0.64, -0.03]) has a 98.46% probability of being negative, 96.83% of being significant, and 59.33% of being large. The effect of Group [TC] on left whole thalamus volume (median = -0.21, 95% CI [-0.51, 0.09]) has a 92.42% probability of being negative, 86.41% of being significant, and 28.77% of being large. The effect of Group [TC] on right medial thalamus volume (median = -0.58, 95% CI [-0.90, -0.25]) has a 99.95% probability of being negative, 99.8% of being significant, and 95.16% of being large. The effect of Group [TC] on left medial thalamus volume (median = -0.47, 95% CI [-0.81, -0.15] has a 99.74% probability of being negative, 99.4% of being significant, and 85.00% of being large. Other subnuclei groups with a high probability of being significant were the left anterior thalamic nuclei and the right anterior thalamic nuclei, however the probability of being large was small, which indicates posterior is mostly contained between the significance and large thresholds.
Conclusions:
Our findings suggest mTBI is associated with thalamic and thalamic subnuclei abnormality toward the end of what is frequently considered the end of the typical recovery period. Whilst our data suggest bilateral whole thalamus and bilateral anterior thalamus are also larger in the mTBI group, the largest effect was identified in the medial thalamic group. Given the medial thalamus sits closest to the midline of the brain, it may be more vulnerable to injury effects in mTBI. Greater volume may reflect thalamic inflammation, which could serve adaptative or maladaptive mechanisms. Further work should investigate the possible mechanisms underpinning increased volume by applying techniques that can probe additional microstructural metrics.
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Subcortical Structures 1
Novel Imaging Acquisition Methods:
Multi-Modal Imaging 2
Keywords:
MRI
STRUCTURAL MRI
Sub-Cortical
Thalamus
Trauma
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
Other - thalamic subnuclei; segmentation; multimodal imaging; traumatic brain injury
1|2Indicates the priority used for review
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