Traumatic Axonal Injury in Patients with Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) is a subtype of TBI that is classified by the severity of head trauma, whereas traumatic axonal injury (TAI) is a diagnostic term with a pathological meaning. In this chapter, TAI in patients with mild TBI is described in terms of definition, history, and diagnostic approach. The presence of TAI in patients with mild TBI has been demonstrated by autopsy studies since the 1960s. However, because conventional brain CT or MRI are not powered with contrast resolution to determine TAI in mild TBI, diagnosis of TAI in live patients with mild TBI was impossible. Since the introduction of diffusion tensor imaging, hundreds of studies have demonstrated TAI in live patients with mild TBI in the 2000s. The precise diagnosis of TAI in patients with mild TBI is clinically important for proper management and prognosis prediction following mild TBI. Several requirements are necessary for diagnosis of TAI in mild TBI: first, head trauma history; second, development of new clinical symptoms and signs after head trauma; third, evidence of TAI of the neural tracts on diffusion tensor imaging or diffusion tensor tractography; and fourth, coincidence of the newly developed clinical features and the function of injured neural tracts