Behavioral and neurocognitive sequelae of concussion in the emergency department

A concussion occurs when the brain is subjected to an acceleration-deceleration force or, as in the case of blast injury, to a pressure wave sufficient to disrupt brain function [1]. The 2013 American Academy of Neurology (AAN) guidelines on the evaluation and management of sports-related concussions define concussion as a "pathophysiologic disturbance in neurologic function characterized by clinical symptoms induced by biomechanical forces, occurring with or without loss of consciousness. Standard structural neuroimaging is normal, and symptoms typically resolve over time [1]." The terms "concussion" and "mild traumatic brain injury" (mTBI) are often used interchangeably in much of the literature and will be used, as well, in this chapter. However, an mTBI diagnosed by a Glasgow Coma Scale (GCS) score of 13-15 simply reflects that the patient at the time of measurement is alert; it is well known that patients can have a significant intracranial lesion, for example, subdural or traumatic subarachnoid, and yet have a GCS of 15. Concussion, on the other hand, implies that not only is the patient awake but also has normal head computed tomography (CT). The International Conference on Concussion in Sport 2012 Zurich Consensus Statement, therefore, describes a concussion as a distinct subtype of mild traumatic brain injury [3]. The decision about which patients should obtain emergent brain imaging in the emergency department is outside the scope of this chapter.