Postconcussional disorder after a relatively mild head injury is common. Although a partial organic etiology is presumed, little imaging evidence exists for this assumption. In this study, patients with mild to moderate brain injury (median Glasgow Coma Scale score of 14) had more parenchymal brain lesions than control subjects (P=0.02). Additionally, the authors investigated the potential of quantifying brain injury by the magnetization transfer ratio (MTR). The curve amplitude of the MTR histogram was used as a measure of normal white matter. Patients had a lower curve amplitude than control subjects (P=0.008). This study provides evidence of persistent traumatic brain alterations in patients who sustained a relatively mild traumatic brain injury.