Much of the recent research concerning mild traumatic brain injury (mTBI) has focused on professional athletes and military veterans. This research may not apply to individuals with mTBI whose injuries result from other causes, including motor vehicle collisions and falls.
Autopsies of individuals with these types of injuries indicate that mTBI causes diffuse axonal injury and micro hemorrhages. Until recently, however, it was not possible to examine microstructural pathology in living persons because of the insufficient sensitivity of computed tomography and conventional magnetic resonance imaging (MRI). Thus, researchers were not able to explore any relationship between mTBI-related structural neuropathology and mTBI-related dysfunction, specifically cognitive impairment.
Technological advances and improved MRI sensitivity now allow researchers to examine microstructural neuropathology in vivo. Within mTBI research, diffusion tensor imaging (DTI) is an MRI-based neuroimaging technique that makes it possible to examine the structural integrity of brain white matter tracts and to estimate the location, orientation, and anisotropy of the white matter tracts. In addition to revealing microstructural damage in vivo after mTBI, these technological advances enable researchers to investigate the in vivo association between mTBI-related structural neuropathology and cognitive dysfunction.
A recent systematic review and meta-analysis of studies examined the relationship between microstructural damage and cognitive function after hospitalized mixed-mechanism mTBI – brain injuries typically caused by motor vehicle collisions and falls – beyond the early acute period. Specific data were extracted from PsycInfo, EMBASE, and MEDLINE including mTBI definitional criteria, descriptive statistics, outcome measures, and results of associations between DTI metrics and cognitive test performance. Of the 248 articles reviewed, eight studies met all inclusion criteria and were included in the meta-analysis.
The meta-analysis revealed statistically significant associations between reduced white matter integrity and poor performance on measures of attention, which persisted beyond one month post-injury.
The findings from the meta-analysis demonstrate for the first time that DTI markers of underlying neuropathology are associated with cognitive function after mTBI. This is the first technique to enable researchers to measure the in vivo relationship between structural neuropathology and cognitive function after mTBI. The results demonstrate that in vivo markers of structural neuropathology are associated with cognitive dysfunction within attention, memory, and executive function.
These findings have important implications for future research and the clinical management of patients with mTBI, especially those patients who do not follow a typical recovery path.