Major or mild NCD due to TBI may be accompanied by disturbances in emotional function
(e.g., irritability, easy frus tration, tension and anxiety, affective lability); personality
changes (e.g., disinhibition, apathy, suspic iousness, aggression); physical disturbances
(e.g., headache, fatigue, slee p disorders, vertigo or dizziness, tinnitus or hyperacusis, pho-
tosensitivity, anosmia, reduced tolerance to psychotropic medication s); and, particularly
in more severe TBI, neurolog ical symptoms and signs (e.g., seizures, hemiparesis, visual
disturbances, cranial nerve deficits) an d evidence of orthopedic injuries.
Prevalence
In the United States, 1.7 million TBIs occur a nnually, resulting in 1.4 million emergency de-
partment visits, 275,000 hospitalizations, and 52,000 deaths. About 2% of the population
lives with TBI-associated disabi lity. Males account for 59% of TBIs in the United States.
The most common etiologies of TBI in the Unit ed States are falls, vehicular accidents, and
being struck on the head. Collisions and blows to the head that occur in the course of con-
tact sports are increasingly re cognized as sources of mild TB I, with a concern that repeated
mild TBI may have cumulatively persisting sequelae.
Development and Course
The severity of a TBI is rated at the time of injury/initial assessment as mild, moderate, or
severe according to the thresholds in Table 2.
The severity rating of the TBI itself does not necessarily correspon d to the severity of
the resulting NCD. The course of recovery fr om TBI is variable, depending not only on the