Classification
No single definition of concussion, minor head injury, or mild traumatic brain injury is universally accepted, though a variety of definitions have been offered. In 2001, the first International Symposium on Concussion in Sport was organized by the International Olympic Committee Medical Commission and other sports federations. A group of experts called the Concussion in Sport Group met there and defined concussion as "a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces." They agreed that concussion typically involves temporary impairment of neurological function that heals by itself within time, and that neuroimaging normally shows no gross structural changes to the brain as the result of the condition.
According to the classic definition, no structural brain damage occurs in concussion; it is a functional state, meaning that symptoms are caused primarily by temporary biochemical changes in neurons, taking place for example at their cell membranes and synapses. However, in recent years researchers have included injuries in which structural damage does occur under the rubric of concussion. According to the National Institute for Health and Clinical Excellence definition, concussion may involve a physiological or physical disruption in the brain's synapses.
Definitions of mild traumatic brain injury (M.T.B.I) have been inconsistent since the 1970s, but the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10) described MTBI-related conditions in 1992, providing a consistent, authoritative definition across specialties. In 1993, the American Congress of Rehabilitation Medicine defined MTBI as 30 minutes or fewer of loss of consciousness (LOC), 24 hours or fewer of post-traumatic amnesia (PTA), and a Glasgow Coma Scale (GCS) score of at least 13. In 1994, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders defined MTBI using PTA and LOC. Other definitions of MTBI incorporate focal neurological deficit and altered mental status, in addition to PTA and GCS.
Concussion falls under the classification of mild TBI. It is not clear whether concussion is implied in mild brain injury or mild head injury. "MTBI" and "concussion" are often treated as synonyms in medical literature. However, other injuries such as intracranial hemorrhages (e.g. intra-axial hematoma, epidural hematoma, and subdural hematoma) are not necessarily precluded in MTBI or mild head injury, but they are in concussion. MTBI associated with abnormal neuroimaging may be considered "complicated MTBI". "Concussion" can be considered to imply a state in which brain function is temporarily impaired and "MTBI" to imply a pathophysiological state, but in practice few researchers and clinicians distinguish between the terms. Descriptions of the condition, including the severity and the area of the brain affected, are now used more often than "concussion" in clinical neurology.
Although the term "concussion" is still used in sports literature as interchangeable with "MHI" or "MTBI", the general clinical medical literature now uses "MTBI" instead.
Controversy exists about whether the definition of concussion should include only those injuries in which loss of consciousness occurs.
Historically, by definition, concussion involved a loss of consciousness. However, the definition has evolved over time to include a change in consciousness, such as amnesia. The best-known concussion grading scales count head injuries in which loss of consciousness does not occur to be mild concussions and those in which it does to be more severe. The Zurich Consensus Statement on Concussion in Sport (Nov. 2008) found unanimous agreement to abandon the simple versus complex terminology that had been proposed in the earlier Prague agreement. The conference participants did, however, find unanimous agreement to keep the concept that most (80–90%) concussions resolve in a short period (7–10 days), although the recovery time frame may be longer in children and adolescents.
Read more about this topic: Concussion