Traumatic brain injury and reserve.

The potential role of brain and cognitive reserve in traumatic brain injury (TBI) is reviewed. Brain reserve capacity (BRC) refers to preinjury quantitative measures such as brain size that relate to outcome. Higher BRC implies threshold differences when clinical deficits will become apparent after injury, where those individuals with higher BRC require more pathology to reach that threshold. Cognitive reserve (CR) refers to how flexibly and efficiently the individual makes use of available brain resources. The CR model suggests the brain actively attempts to cope with brain damage by using pre-existing cognitive processing approaches or by enlisting compensatory approaches. Standard proxies for CR include education and IQ although this has expanded to include literacy, occupational attainment, engagement in leisure activities, and the integrity of social networks. Most research on BRC and CR has taken place in aging and degenerative disease but these concepts likely apply to the effects of TBI, especially with regards to recovery. Since high rates of TBI occur in those under age 35, both CR and BRC factors likely relate to how the individual copes with TBI over the lifespan. These factors may be particularly relevant to the relationship of developing dementia in the individual who has sustained a TBI earlier in life.