Multimodal imaging of mild traumatic brain injury and persistent postconcussion syndrome.
BACKGROUND
Persistent postconcussion syndrome (PCS) occurs in around 5-10% of individuals after mild traumatic brain injury (mTBI), but research into the underlying biology of these ongoing symptoms is limited and inconsistent. One reason for this could be the heterogeneity inherent to mTBI, with individualized injury mechanisms and psychological factors. A multimodal imaging study may be able to characterize the injury better.


OBJECTIVE
To look at the relationship between functional (fMRI), structural (diffusion tensor imaging), and metabolic (magnetic resonance spectroscopy) data in the same participants in the long term (>1 year) after injury. It was hypothesized that only those mTBI participants with persistent PCS would show functional changes, and that these changes would be related to reduced structural integrity and altered metabolite concentrations.


METHODS
Functional changes associated with persistent PCS after mTBI (>1 year postinjury) were investigated in participants with and without PCS (both n = 8) and non-head injured participants (n = 9) during performance of working memory and attention/processing speed tasks. Correlation analyses were performed to look at the relationship between the functional data and structural and metabolic alterations in the same participants.


RESULTS
There were no behavioral differences between the groups, but participants with greater PCS symptoms exhibited greater activation in attention-related areas (anterior cingulate), along with reduced activation in temporal, default mode network, and working memory areas (left prefrontal) as cognitive load was increased from the easiest to the most difficult task. Functional changes in these areas correlated with reduced structural integrity in corpus callosum and anterior white matter, and reduced creatine concentration in right dorsolateral prefrontal cortex.


CONCLUSIONS
These data suggest that the top-down attentional regulation and deactivation of task-irrelevant areas may be compensating for the reduction in working memory capacity and variation in white matter transmission caused by the structural and metabolic changes after injury. This may in turn be contributing to secondary PCS symptoms such as fatigue and headache. Further research is required using multimodal data to investigate the mechanisms of injury after mTBI, but also to aid individualized diagnosis and prognosis.
School of Psychology, University Of Surrey Guildford, UK.
Philip Ja
PJ
Dean
Center of Mathematics, Computation and Cognition, Universidade Federal do ABC São Paulo, Brazil ; NIF/LIM44, Departamento de Radiologia da Faculdade de Medicina da Universidade de São Paulo São Paulo, Brazil.
Joao R
JR
Sato
NIF/LIM44, Departamento de Radiologia da Faculdade de Medicina da Universidade de São Paulo São Paulo, Brazil.
Gilson
G
Vieira
School of Psychology, University Of Surrey Guildford, UK.
Adam
A
McNamara
School of Psychology, University Of Surrey Guildford, UK.
Annette
A
Sterr
D000293:Adolescent; D000328:Adult; D001930:Brain Injuries / Q000175:diagnosis*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D064847:Multimodal Imaging; D038223:Post-Concussion Syndrome / Q000175:diagnosis*; D055815:Young Adult
Cognitive tasks; mild traumatic brain injury; neuroimaging