Rees PM. Contemporary issues in mild traumatic brain injury. Arch Phys Med Rehabil 2003;84:1885–94. Objectives To determine (1) minimum criteria in adults for clinical diagnosis of mild traumatic brain injury (TBI) and (2) whether persistent postconcussive syndrome exists as a nosologic entity. Data sources PubMed search by MEDLINE of head injuries from January 1977 to July 2002. Study selection All reviews and studies of mild TBI with special reference to those on persistent postconcussive syndrome having a general trauma cohort as a control comparison. Data extraction Review of design and other methodologic issues. Studies dependent on superior strength of evidence (as defined by the American Academy of Neurology) concerning the biologic nature of persistent postconcussive syndrome. Data synthesis A period of altered awareness with amnesia brought on by a direct craniofacial blow is the starting point in determining whether diffuse mild TBI has occurred. An amnestic scale is more helpful than Glasgow Coma Scale score in grading mild injury and in formulating minimum inclusion criteria for mild TBI. Neuropsychologic test results coupled with self-reported symptoms should not be taken as the primary source of evidence for mild TBI. Prolonged cognitive impairment after injury is not unique to brain trauma. Conclusions Persistent postconcussive syndrome after mild brain trauma, uncomplicated by focal injury, is biologically inseparable from other examples of the posttraumatic syndrome. To account for the persistent cognitive and behavioral sequelae of posttraumatic states, including persistent postconcussive syndrome, we need further studies on the emerging concept of limbic neuronal attrition occurring as a maladaptive response to pain and stress.