Clinical Context and Diagnostic Criteria

TBI is a major cause of morbidity and mortality worldwide. Each year, in the United States alone, more than 2.5 million TBIs occur; over 55,000 individuals die, over 300,000 are hospitalized, and more than 2 million are treated and released from emergency departments.2 An unknown but likely very large number of TBIs are unrecognized or dismissed.3

TBI is commonly classified as to its severity based on clinical examination at the time of injury. This classification, based largely on the Glasgow Coma Scale (GCS; scale range 3-15), delineates severe (GCS 3-8), moderate (GCS 9-12), and mild (GCS 13-15) TBI. This GCS-based classification is an excellent predictor of survival to hospital discharge, but does not effectively predict long-term outcome, especially with more mild degrees of injury.4 Additional factors used for classification include the duration of unconsciousness, the duration of posttraumatic amnesia, and the presence of focal neurological deficits and imaging ab- normalities.56

Mild TBI (mTBI, also termed concussion) is the most common form of TBI.2 Patients with mTBI experience a disturbance of neurocognitive function following the injury, which may include confusion, disorientation, imbalance, and other features. Some, but by no means all, mTBI patients experience actual loss of consciousness.7 Diagnostic criteria for mTBI include no more than 30 minutes of unconsciousness, no more than 24 hours of amnesia, and absence of focal neurological deficits.8 mTBI is typically not associated with abnormalities on conventional computed tomography (CT) and magnetic resonance imaging (MRI).1 Notwithstanding the relatively mild initial clinical features and absence of conventional imaging abnormalities, clinical manifestations of mTBI do arise from brain pathology, particularly traumatic axonal injury (TAI).9

Most patients with mTBI will recover, but a significant minority (15-30%,) will sustain long-term adverse consequences, including persistent post- concussive symptoms, cognitive impairment, and behavioral dysfunction.7 Thus the consequences of “mild” TBI are by no means necessarily mild. High- profile coverage of sports and military-related mTBI and its long-term adverse effects, including delayed neurodegenerative disorders, such as chronic traumatic encephalopathy (CTE),10 have driven increased awareness of mTBI. Patients with GCS scores in the mTBI range (13-15) who do have gross imaging abnormalities are often classified as mild-complicated TBI. These individuals may have worse prognosis for recovery.11

< Prev   CONTENTS   Source   Next >