"I won't be witness to the results when I donate my brain, and I hope that day is a long way from today, but I'm hoping that my donation helps change things for the positive," Chastain told the Concussion Legacy Foundation.
"I can't even attempt a guess at how many times I've headed the ball. It's a significant number. It's scary to think about all the heading and potential concussions that were never diagnosed in my life, but it's better to know."
Chronic traumatic encephalopathy, or CTE, is closely linked with the repeated head injuries commonly experienced in contact sports and can lead to aggression and dementia.
Chastain, who made the last of her 192 appearances with the U.S. national team in 2004, is the latest in a growing list of current and former athletes who have agreed to donate their brains after death.
A high incidence of degenerative brain disease in former professional American football players led thousands of National Football League alumni to press for and win a settlement that could cost the league $1 billion.
Chastain is perhaps best remembered for removing her shirt during a memorable and controversial goal celebration after she scored the winning penalty kick that decided the shootout against China in the 1999 Women's World Cup final.
"Brandi Chastain's decision to donate her brain to further research is a powerful and courageous act that will ultimately improve the future health of female athletes, military veterans and other women who experience repetitive brain trauma," Ann McKee, director of Boston University's CTE program, said in a statement.
"We currently know so little about how gender influences outcome after trauma; her pledge marks an important step to expand our knowledge in this critical area."
(Reporting by Frank Pingue in Toronto; Editing by Mark Lamport-Stokes)
