Advanced Neuroimaging of Mild Traumatic Brain Injury

In the acute clinical setting both computed tomography (CT) and conventional magnetic resonance imaging (MRI) are established imaging modalities to rule out severe complications resulting from traumatic brain injury (TBI) such as skull fracture, intracranial hemorrhage, and brain edema. However, when applied to mild traumatic brain injury (mTBI) only about 10% of CT scans and 30% of MR scans reveal abnormalities such as subdural or subarachnoidal hemorrhage.– Moreover, conventional CT and MRI have proven insensitive to more subtle changes in the brain such as diffuse axonal injury, the most common injury present in mTBI. Furthermore, these conventional imaging modalities do not provide accurate information relevant to long-term prognosis.,,In search of radiological evidence for mTBI, what are needed are highly sensitive, as well as objective measures of early detection (diagnosis) and accurate prognosis. Several promising advances in neuroimaging techniques are currently available and will be evaluated here. We review promising imaging techniques and their application to understanding brain abnormalities following mTBI and repetitive brain trauma. These imaging techniques include techniques to understand brain structure (high-resolution structural MR imaging) and tissue architecture (diffusion tensor imaging), techniques to understand regional blood flow (dynamic susceptibility contrast MR imaging, arterial spin labeling, single photon emission tomography), techniques to evaluate microhemorrhages (susceptibility-weighted imaging), and, finally, techniques used as indirect measures of neuronal activation (functional MR imaging) and brain metabolism (positron-emission tomography, MR spectroscopy).