Mild Traumatic Brain Injury

Abstract

  Mild traumatic brain injury (MTBI) was first advocated by the American Association of Rehabilitation Medicine (ACRM) in 1993 and was defined as an alteration of brain function attributable to external forces with one or more of the following : loss of consciousness for 0-30 minutes, post-traumatic amnesia for less than 24 hours, focal neurologic deficits that may or may not be transient, and an alteration of mental state at the time of the accident, including any confusion, disorientation, or slowed thinking. Per ACRM definition, MTBI is defined mainly for subjective symptoms and does not consider objective findings, such as severity and diagnostic imaging. Because of this confusion, the World Health Organization Collaborating Centre for Neurotrauma Task Force on MTBI proposed its definition based on the review of the literature in 2004. Their criteria are similar to those proposed by ACRM, except they specify the use of a Glasgow Coma Scale score of 13-15 at the presentation time to a healthcare professional instead of restricting it to a score within 30 minutes. Further, a systematic review conducted in 2014 based on this definition reported frequent incidence of cognitive impairment of MTBI for 2 weeks after injury and consciousness disorder. However, MTBI-related cognitive deficits were found to recover within a year after injury, and most of them were cerebral concussions. A concussion is representative of mild head trauma, and a single concussion does not lead to brain dysfunction, such as permanent cognitive impairment. In Japan, the term “MTBI” does not exist as a disease name in neurosurgery, nor is it a medical term with a unified definition. However, MTBI is confused with “mild head injury,” and the term is easily used when claiming damage. Even if a brain injury is present in “mild head trauma,” mild trauma does not cause organic brain injury. In this review, we explain the term “MTBI” and focus on associated cognitive dysfunction from our case studies and literature review.