Simplification for small and big stretches
For small strains, the exponential term is very small, thus negligible.
It is frequently stated in the literature and considered to be common knowledge that 15–30% of people with PCS have not recovered by a year after the injury, but this estimate is imprecise because it is based on studies of people admitted to a hospital, the methodologies of which have been criticized. In approximately 15% of people, symptoms may persist for years or be permanent. If symptoms are not resolved by one year, they are likely to be permanent, though improvements may occur after even two or three years, or may suddenly occur after a long time without much improvement. Older people and those who have previously had another head injury are likely to take longer to recover.The way in which children cope with the injury after it occurs may have more of an impact than factors that existed prior to the injury. Childrens mechanisms for dealing with their injuries may have an effect on the duration of symptoms, and parents who do not deal effectively with anxiety about childrens post-injury functioning may be less able to help their children recover.If another blow to the head occurs after a concussion but before its symptoms have gone away, there is a slight risk of developing the serious second-impact syndrome (SIS). In SIS, the brain rapidly swells, greatly increasing intracranial pressure.