Excessive brain cell growth after head injury bad for brain

Turning conventional wisdom on its head, researchers including one of Indian-origin, have found that the excessive burst of new brain cells after a traumatic head injury that scientists have traditionally believed helped in recovery could instead lead to epileptic seizures and long-term cognitive decline.

The findings published in the journal Stem Cell Reports suggest that memory decline after head injury may be prevented by slowing brain cell growth. 

"There is an initial increase in birth of new neurons after a brain injury but within weeks, there is a dramatic decrease in the normal rate at which neurons are born, depleting brain cells that under normal circumstances should be there to replace damaged cells and repair the brain's network," said Vijayalakshmi Santhakumar, Associate Professor at Rutgers New Jersey Medical School in the US. 

"The excess new neurons lead to epileptic seizures and could contribute to cognitive decline," she added.

Symptoms of traumatic brain injury can include impaired thinking or memory, personality changes and depression and vision and hearing problems as well as epilepsy. 

About 80 percent of those who develop epilepsy after a brain injury have seizures within the first two years after the damage occurs.

While researchers who study epilepsy have started to look more closely at how preventing excessive neurogenesis (the birth of new brain cells) after brain injury could prevent seizures, neuroscientists have traditionally viewed the process as helpful to overall brain recovery, Santhakumar said. 

Studying laboratory rats, the scientists found that within a month after experimental brain injury, the number of new brain cells declined dramatically, below the numbers of new neurons that would have been detected if an injury had not occurred.

When scientists were able to prevent the excessive neurogenesis which occurs within days of the injury with a drug similar to one under trial for chemotherapy treatments, the rate of birth of new brain cells went back to normal levels and risk for seizures was reduced.

"That's why we believe that limiting this process might be beneficial to stopping seizures after brain injury," Santhakumar said.

While the regenerative capability of brain cells, in the hippocampus -- the part of the brain responsible for learning and memory -- slows down as part of the ageing process, the scientists determined that the process that occurred after a head injury was related to injury and not age.