Functional neuroimaging of traumatic brain injury: advances and clinical utility

Figures & data

Table 1 Summary of major clinical goals whose achievement can benefit from functional neuroimaging studies

Clinical goal	Study	Findings and conclusions
Distinguish between vegetative, minimally conscious, and locked-in patients	Garcia-Panach et al^Citation4	• Glucose hypometabolism in the precuneus and temporal cortex of vegetative and minimally-conscious patients • Cortico-thalamo-cortical metabolism correlated with functional outcome • Posttraumatic hypometabolism resolves in tandem with neurological deficits • PET may aid in distinguishing between vegetative-state and minimally-conscious state patients, but future studies should try to ascertain the link between hypometabolism, focal damage, and DAI
	Bruno et al^Citation6	• Patients who exhibit nonbehavioral evidence of consciousness should be assumed to exhibit locked-in syndrome
	Owen and Coleman^Citation7	• TBI patients in vegetative state can exhibit robust activation in parahippocampal and supplementary motor areas
	Schnakers et al^Citation8,Citation9	• Measurements of cerebral blood flow changes, glucose utilization, and electrophysiological activation hold promise for distinguishing between patients who are locked-in, minimally conscious, or in a vegetative state
Design novel interventions to reduce motor deficits after TBI	Kasahara et al^Citation11,Citation23	• Motor function damage after TBI is partially due to DAI and massive reorganization of motor activation cortex • M1, the cerebellum and supplementary motor area, exhibit reduced interhemispheric interaction and abnormal ipsilateral interactions with supramarginal areas • Poor interaction between the cerebellum and M1 suggests that DAI is partly responsible for the loss of motor acuity • Functional deterioration in the supramarginal gyrus may indicate that DMN deterioration leads to motor function loss
	Leunissen et al^Citation10,Citation18	• During motor switching, white matter damage causes overactivation of supplementary motor and inferior frontal areas, and underactivation of subthalamic nuclei
	Babikian et al^Citation19	• Altered interhemispheric communication mediated by the corpus callosum is correlated with changes in neurocognitive function • Multimodal studies using PET and MRS should be prioritized to understand how motor deficits may be alleviated by clinical interventions aiming to maintain metabolic homeostasis
Determine how clinical care can be improved to alleviate memory deficits	Garcia-Panach et al^Citation4	• TBI patients with posttraumatic amnesia exhibit metabolic dysfunction in orbitofrontal and medial temporal areas • Studies are needed to determine whether clinical interventions aimed at minimizing secondary injury to these regions can minimize memory deficits
	Kasahara et al^Citation11,Citation23	• At high memory loads, TBI patients have reduced activation in the left inferior parietal gyrus and increased activation in the right inferior frontal gyrus
	Palacios et al^Citation24,Citation33	• TBI patients have abnormal overlap between working memory networks and the DMN, suggesting that the DMN is altered in patients with poor memory • Though structural alterations in brain connectivity have been implicated in damage to working memory networks, larger samples are needed to evaluate the viability of connectivity analysis and the generalizability of its findings for clinical purposes
	Kim et al^Citation25	• The superior occipital cortex and temporal areas can become functionally overactive during visual attention tasks • Attentional modulation deficits due to TBI exacerbate memory dysfunction
	Marquez de la Plata et al^Citation26	• In TBI patients, the hippocampus and the anterior cingulate cortex exhibit lower interhemispheric connectivity
Identify how rehabilitation can minimize loss of cognitive control after brain injury	Sponheim et al^Citation28	• Brain injury leads to worsening of interhemispheric coordination, which can be quantified using scalp EEG • Damaged frontal lobe connectivity can lead to poor coordination of frontal neural functions independently of mental health symptoms • The relationship between cognitive control and interhemispheric communication is likely significant and should be investigated multimodally
	Pandit et al^Citation34	• Cognitive control networks can lose their small-world characteristics after TBI • When affected by DAI, the posterior cingulate cortex can lose its status as a brain network hub and thereby accelerate the deterioration of cognitive control
Formulate clinical strategies to alleviate personality changes	Choe et al^Citation39	• Subsequent to pediatric TBI, personality deficits may develop long after injury, despite negative findings on conventional CT or MRI scans • Damage due to recurrent concussions during childhood should be investigated using advanced DTI/DSI imaging to alert patients against risky behaviors
	Vaishnavi et al^Citation47	• Because imaging studies have been slow to provide solid empirical findings which can guide patient treatment, research on the relationship between mood disturbance severity and functional brain changes prompted by TBI should be prioritized

Notes: Listed to the right of each goal are a selection of studies discussed in the review as well as their major findings and conclusions. The reader is referred to the text for detailed discussions of each reviewed study.

Abbreviations: CT, computed tomography; DAI, diffuse axonal injury; DMN, default mode network; DTI, diffusion tensor imaging; DSI, diffusion spectrum imaging; EEG, electroencephalography; MRI, magnetic resonance imaging; MRS, magnetic resonance spectroscopy; M1, primary motor cortex; PET, positron emission tomography; TBI, traumatic brain injury.

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