626 Neurocognitive Disorders
Neurobehavioral symptoms tend to be most severe in the immediate aftermath of the
TBI. Except in the case of severe TBI, the typi cal course is that of complete or substantial
improvement in associated neurocognitive, neurological, and psyc hiatric symptoms and
signs. Neurocognitive symptoms associated with mild TBI tend to resolve within days to
weeks after the injury with complete resoluti on typical by 3 months. Other symptoms that
may potentially co-occur with the neurological  symptoms (e.g., depression, irritability,
fatigue, headache, photosensitivity, sleep dist urbance) also tend to resolve in the weeks
following mild TBI. Substantial subsequent deterioration in these areas should trigger con-
sideration of additional diagnoses. However,  repeated mild TBI may be associated with
persisting neurocognitive disturbance. 
With moderate and severe TBI, in addition to persistence of neurocognitive deficits,
there may be associated neurophysiological, emotional, and behavi oral complications.
These include seizures (particula rly in the first year), photosen sitivity, hyperacu sis, irritabil-
ity, aggression, depression, sl eep disturbance, fatigue, apat hy, inability to resume occu-
pational and social functioning at pre-injury level, and deterioration in interpersonal
relationships. Moderate and seve re TBI have been associated with increased risk of depres-
sion, aggression, and possibly  neurodegenerative diseases such as Alzheimer’s disease.
The features of persisting majo r or mild NCD due to TBI will vary by age, specifics of
the injury, and cofactors. Persisting TBI-related impairment in an infant or child may be re-
flected in delays in reaching developmental mi lestones (e.g., language acquisition), worse