For many years it has been medical gospel that symptoms of a traumatic brain injury will appear immediately after the impact and will thereafter decrease over the passage of time through recovery. However, more research into the biological impact of TBI at the cellular level suggest that some of the damage to the brain tissue following trauma can continue for months and even years after the time of trauma. There are also other factors which make this a formally “gospel” of symptom onset antiquated and untrue in many cases.
Canadian researchers (Doucher PA, et al. 2010) looked at how even initially mild axon damage tends to worsen in hours, days and even weeks after a head injury. They found that within axon cells (white matter fibers that transmit information between lobes of the brain) trauma adversely affects the crucial pumping systems within the brain cell, throwing the healthy percentage of different chemicals in the cell out of whack, causing cell death. In particular, the sodium, calcium, and potassium levels become excitotoxic, in which the electrical current in the cell is out of whack causing degeneration and death of the cell.
It is well known now that brain atrophy can appear even in the context of a mild traumatic brain injury. Because of brain swelling, there are a few studies which indicate how much brain atrophy occurs within the first two months after injury, but one study suggested that most of the atrophy takes place during this time. However, in cases of moderate and severe TBI, follow up studies have shown that the atrophy in the brain continues occurring at above normal aging rates, for a year and more. Studies of the pathological chemical reactions following traumatic brain injury can continue to be found four years after the initial injury. Using spectroscopy, which measures the exact correlation of chemical products within the brain, they have found that traumatized brains keep this adverse composition of brain matter and thus ongoing symptoms, for years following impact.
Finally, onset is often “delayed” because the victim, post injury, is doing nothing to tax the brain. Two weeks in bed or off work or school, with no multi-tasking or complex social environment to deal with can give the illusion “that all is well.” Even after returning to work or school, it can take months to fully realize or admit that “things are not right.” Often friends and family gently point this out.
Victims should not be penalized by insurance companies for human nature – hoping they will be okay and going back to work. Instead adverse psychological symptoms snowball and become worse. This can also account for reports of significant impairment arising months after trauma
Overall, the research shows delayed biological events in the brain for months or a year post impact. Treating doctors need to be aware of this.