From The Scientist
On September 13, 1848, a 25-year-old railroad worker named Phineas Gage triggered an explosion that propelled a 3 foot 7 inch iron rod straight through his skull, destroying a good portion of his brain. Luckily, the iron missed the critical blood vessels and parts of the brain necessary for survival, but the injury spurred dramatic behavioral changes and made Gage’s accident one of the most important contributions to modern neurology.This is indeed a very famous incident. From what I've read about Gage, his mental changes did not diminish, but he was able to function reasonably well.
“This was the first case when doctors made a definite connection between an injury to the brain and a change in personality,” says Malcolm Macmillan, a professor of behavioral science at the University of Melbourne in Australia and an expert on Gage. Linking the damage in Gage’s prefrontal cortex to his sudden erratic behavior was one of the first clues that the prefrontal cortex was responsible for personality expression and decision making.
Because Gage made public appearances and worked after the injury, Macmillan hypothesized that his personality change must have been “a temporary one” and “that he made a good psychosocial recovery.” Macmillan found further support for this theory when, in 2008, photographers Jack and Beverly Wilgus from Massachusetts revealed an image of Gage holding the pole that had shot through his brain. The picture, which they had possessed for 30 years but only recently identified as Gage, displays a handsome, proud, and confident-looking man.
“The image suggests that Phineas had adapted to his disfigurement and was not ashamed to display it,” writes Macmillan in an email. Gage’s mental improvement suggests that it’s possible for the brain to recover some of its function after an injury, he adds, although the details of Gage’s recovery remain a mystery.