Hidden Truth in Cerebral Concussion—Traumatic Axonal Injury: A Narrative Mini-Review

This study reviewed traumatic axonal injury (TAI) in patients with concussion. Concussion refers to transient changes in the neurological function of the brain resulting from head trauma that should not involve any organic brain injury. On the other hand, TAI has been reported in autopsy studies of the human brain and histopathological studies of animal brains following concussion before the development of diffusion tensor imaging (DTI). The diagnosis of TAI in live patients with concussion is limited because of the low resolution of conventional brain magnetic resonance imaging. Since the first study by Arfanakis et al. in 2002, several hundred studies have reported TAI in patients with concussion using DTI. Furthermore, dozens of studies have demonstrated TAI using diffusion tensor tractography for various neural tracts in individual patients with concussion. Hence, DTI provides valuable data for the diagnosis of TAI in patients with concussion. Nevertheless, the confirmation of TAI in live patients with concussion can be limited because a histopathological study via a brain biopsy is required to confirm TAI. Accordingly, further studies for a diagnostic approach to TAI using DTI without a histopathological test in individual patients with concussion will be necessary in the clinical field.