Magnetoencephalography and High-field Diffusion Tensor Magnetic Resonance Imaging of Brain Function and Connectivity in Head Trauma With Post-concussive Syndrome

Pratik Mukherjee, M.D., Ph.D.

University of California

Funded in June, 2006: $100000 for 2 years
LAY SUMMARY . ABSTRACT . HYPOTHESIS .

LAY SUMMARY

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Combining Two Imaging Techniques to Predict Outcomes of Traumatic Brain Injury

The researchers aim to improve the diagnosis and prognosis of traumatic brain injuries.  They will combine two imaging techniques that they anticipate will enable clinicians to directly visualize both the brain’s functioning and its neuronal connections (“wiring”).   

Even mild traumatic brain injuries can produce cognitive deficits and psychiatric disturbances. Currently used CT scans often fail to identify head injury, and MRI scans do not provide information consistently enough to assess a patient’s prognosis.  The researchers hypothesize that long-term cognitive and behavioral effects are due to selective disruption of long-range neural pathways that connect the two cerebral hemispheres, producing functional impairment of the network of brain regions (white matter) that are interconnected by these pathways.

They propose to use diffusion-tensor imaging (DTI) to measure traumatic white matter injury and magnetoencephalography (MEG) to detect impaired cortical activation, and they expect that the combined results will correlate with neurocognitive status and functional recovery following traumatic brain injury. They will compare imaging results from patients experiencing symptoms following head injury, over time, with those from healthy volunteers, to determine whether this combined use of MEG and DTI provide valid biomarkers for predicting long-term outcomes from head injuries.

Significance:  If the combined use of MEG and DTI is found to accurately identify and characterize head injury, this method could become a standard tool for basing decisions on treatment and rehabilitation approaches and for assessing the effectiveness of experimental therapeutic and rehabilitative interventions.

ABSTRACT

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Magnetoencephalography and High-field Diffusion Tensor Magnetic Resonance Imaging of Brain Function and Connectivity in Head Trauma With Post-concussive Syndrome

The overall hypothesis of this project is that the long-term cognitive and behavioral sequelae of traumatic brain injury (TBI) are due to selective disruption of the long association white matter tracts of the cerebral hemispheres, with resulting functional impairment of the network of cortical regions that are interconnected by these long-range association pathways. We propose that traumatic white matter injury can be measured with diffusion tensor imaging (DTI), that the impaired cortical activation can be detected with magnetoencephalography (MEG), and that the results of these imaging examinations will correlate with neurocognitive status and functional recovery after TBI.

The novel aspects of this investigation are twofold. First, damage to white matter tracts will be assessed using a 3 Tesla MR scanner with parallel imaging capability to perform DTI at higher spatial resolution and with better image quality than has been previously achieved in this patient population. Second, a state-of-the-art 275-channel whole-head MEG system will be used to gauge functional brain activation after TBI, employing novel 5-dimensional broadband beamformer reconstruction methods to better localize and more fully characterize event-related activity evoked by well-established stimulation paradigms. The long-term objective of this research is to validate quantitative MEG and DTI biomarkers for predicting patient outcome after TBI, for assessing neuroplasticity during the recovery phase after TBI, and for monitoring the efficacy of therapeutic interventions and rehabilitation.

HYPOTHESIS

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Hypothesis:
The overall hypothesis is that the long-term cognitive and behavioral sequelae of traumatic brain injury (TBI) are due to selective disruption of the long association white matter tracts of the cerebral hemispheres, with resulting functional impairment of the network of cortical regions that are interconnected by these long-range association pathways.

Goals:
1. To measure white matter tract disruption in chronic symptomatic TBI with diffusion tensor imaging (DTI).

2. To detect altered cortical activation related to speech, memory, attention, and cognitive control in symptomatic TBI patients using magnetoencephalography (MEG).

3. To relate the pathology found by DTI and MEG to functional recovery after TBI using neurocognitive and behavioral testing.

Methods:
Traumatic white matter injury will be measured with diffusion tensor imaging (DTI), an advanced form of MRI that can quantitatively assess pathology in functionally specific white matter pathways.  Impaired cortical activation seen in symptomatic TBI will be detected with magnetoencephalography (MEG), which localizes the magnetic field changes associated with neural activity.