While past battles with skin cancer has received a great deal of scrutiny, near-fatal aneurysms in 1988 have yet to come under the spotlight.
Soon after ending his first presidential bid that year, Biden, who had been suffering from what he thought were headaches and a pinched nerve, collapsed in a hotel room shortly after giving a speech on foreign policy.
In his book "Promises to Keep," Biden says that he was unconscious for over four hours before he woke up in a hospital in Wilmington, Del. The senator was told that an artery was leaking blood into his brain and he was given his last rites by a priest. He was transferred to Walter Reed Medical Center where it was discovered that he had a second aneurysm on the other side of his brain.
Biden immediately underwent a four-and-a-half-hour operation to remove the leaking aneurysm. He had a second surgery in May to repair the other aneurysm and fully recovered after taking a seven-month leave from his seat as chairman of the Senate Judiciary Committee.
Following the memorial service of Rep. Stephanie Tubbs Jones, who died in August of an aneurysm, Biden said, "I know it sounds corny, it almost sounds maudlin, but you know, here she was one day walking around, just like I was the next day.
"I woke up four hours later on the floor with a hemorrhage. In her case, the same thing happened, only she never made it back."
Dr. Anthony J. Caputy, chairman of the neurology department at George Washington University Hospital, said that after being treated for the aneurysms, Biden is "highly unlikely" to experience the problem again.
"Once they're dealt with, they're dealt with," Caputy said. "The likelihood that he would ever have any trouble is very small, even smaller than the general population."
Biden, now 67 years old, has yet to release his medical history, of which the aneurysms are one of the few known episodes.
Biden's spokesman David Wade told Politico that "we intend to make available his medical history before the election."
He added that "Sen. Biden is in terrific health and he's full of unbridled energy on the campaign trail. He leads an active lifestyle, works out regularly even as he campaigns, and his wife and family always make sure he drinks plenty of water and eats right. After a health scare over 20 years ago, he's been blessed with excellent health."
Like Biden, McCain's running matehas not yet released her medical records. Spokesman Ben Porritt said only "we have no announcement at this time."
McCain, who is four years older than Biden, provided access to nearly 2,000 pages of his recent medical history in May following questions about his history of melanoma and concerns about his age.
McCain has had four procedures to remove melanoma, a type of skin cancer that can be fatal if it spreads to other organs. He has had more than a dozen such patches of abnormal skin removed.
The Republican had his most severe surgery in 2000, when a large Stage IIa melanoma on the left side of his face, along with 38 lymph nodes and a gland that proved to be cancer free, was removed. He has been cancer free since.
The ten-year survival rate of patients who have had a Stage II melanoma is roughly 65 percent.
On a conference call with reporters following the release of McCain's medical records, the senator's personal physician, John Eckstein, said, "Sen. McCain enjoys excellent heath and displays extraordinary energy."
"There is no medical reason or problem that would preclude Sen. McCain from fulfilling all of the duties and obligations as president of the United States."
Still McCain's health has been an issue, especially after selecting Palin as his running mate. Democrats frequently questioned her experience by pointing out that if elcted, she would be "a heartbeat from the presidency," a thinly veiled shot at McCain's age and previous medical concerns.
Soon after the Palin pick, topsurrogate Sen. Claire McCaskill (D-Mo.) invoked McCain's history of skin cancer on ABC's "This Week," telling host George Stephanopoulos, "I think what we're talking about is a reality. Other people talk about his melanoma. We're talking about a reality here that we have to face. This is someone who's going to be one heartbeat away from the presidency. All of us know it. I just think that it's the facts."
Obama released a brief letter summarizing his medical history shortly after McCain made his medical records available. The summary, written by Dr. David L. Scheiner, revealed that Obama had struggled to quit smoking but is overall in "excellent health."
The line most media outlets seized on from the summary is that Obama is "lean and muscular with no excess body fat."
While the short letter released by the Democrat's campaign praised his diet and fitness regime, the full disclosure McCain provided opened him up to some embarrassment. One note in a report from McCain's oncologist, Dr. Suzanne Connolly, drew particular interest: "Buttocks unremarkable except for some very light tan freckling."
By Andy Barr