Question of the day: Did Lou Gehrig really have Lou Gehrig's disease?

Or did the Mayo Clinic make a historic mistake when it made the diagnosis 71 years ago, forever linking the world-famous New York Yankee with an obscure neurological illness?

A new medical study has suddenly cast into doubt whether Gehrig, who died in 1941, ever had the degenerative disease that bears his name -- officially known as amyotrophic lateral sclerosis (ALS).

Researchers at Boston University have found that head injuries -- which Gehrig suffered repeatedly during his baseball career -- can damage the central nervous system in a way that mimics the disease.

And while they didn't study Gehrig himself, the researchers acknowledged that their findings could rewrite the history books about the man who famously stood at Yankee Stadium in 1939, his career cut short by illness, calling himself "the luckiest man on the face of the earth."

"Here he is, the face of his disease, and he may have had a different disease as a result of his athletic experience," said Dr. Ann McKee, director of neuropathology at the New England Veterans Administration Medical Centers, and the lead author on the study published Wednesday.

The Mayo Clinic, however, is remaining mum about Gehrig's condition: patient confidentiality still rules, even for legends. Still, it says there's good reason to worry about the risk of head injuries among athletes, whether or not they played a role in Gehrig's death.

Today, head injuries are taken much more seriously than in Gehrig's day, when baseball players didn't even wear batting helmets. Twins first baseman Justin Morneau has been on the disabled list since July 7, and Pierre-Marc Bouchard of the Wild has been sidelined for a year, both following concussions during games.

Some are misdiagnosed

In recent years, several studies have suggested that professional football and soccer players, as well as combat veterans, have unusually high rates of ALS. Wednesday's study suggests that sports injuries may play an even greater role than previously thought in degenerative diseases.

"People are being misdiagnosed clinically while they're alive as having ALS when in fact they have a different motor-neuron disease," said Dr. Robert Stern, who serves with McKee as co-director of Boston University's Center for the Study of Traumatic Encephalopathy.

For this study, according to the New York Times, scientists tested the spinal cords of two deceased National Football League players and a professional boxer who had been diagnosed with ALS. None of the three had the characteristic markings of ALS, which destroys nerve cells in the brain and spinal cord, the study found. Instead, the scientists concluded that all three -- including Wally Hilgenberg, a linebacker with the Minnesota Vikings in the 1970s -- had a different fatal disease caused by concussion-like trauma.

No such test could be done on Gehrig because his remains were cremated; his name doesn't even appear in the study. But the Yankees legend had a well-documented history of significant concussions on the baseball field, and perhaps others as a football halfback in high school and at Columbia University.

News reports during his career show that he was knocked unconscious at least four times while at bat, playing first base and in a post-game brawl with fellow baseball icon Ty Cobb. Given that, it's possible that Gehrig's renowned commitment to playing through injuries like concussions, which resulted in his legendary streak of playing in 2,130 consecutive games, could have led to his condition.

Gehrig's symptoms first surfaced in 1938 when his hands began to ache and his legs and shoulders gradually weakened. At spring training in 1939, even casual observers could see that something was quite wrong. That May, he missed his first game in 14 years, ending his historic streak, and by June he was headed to the Mayo Clinic in Rochester. At the time, ALS was a virtually unknown disease, and doctors described it as a form of "infantile paralysis" resembling polio. With no known cause or cure, it eventually causes the loss of muscle control throughout the body. ALS had been in the medical books since 1869, but after 1939, everyone knew it as "Lou Gehrig's Disease."

A Mayo mistake?

As a matter of policy, Mayo won't talk about a patient without permission; and Gehrig has no descendents, meaning his medical records likely are sealed forever, said spokeswoman Elizabeth Rice.

But Dr. Eric Sorenson, a Mayo Clinic neurologist and ALS expert, said that even though diagnostic techniques were less precise 70 years ago, they were pretty accurate. Basically, doctors would identify it by the distinct pattern of symptoms and the way the patient got progressively worse. "In most cases, it's not challenging to diagnose," he said. Today, there's also a muscle test to help narrow the diagnosis, but no proof without an autopsy.

Sorenson said he hadn't seen the latest study, although he's eager to do so. He noted that there's still debate about whether athletes actually have higher rates of ALS, because studies have been inconclusive.

But there's no debate, he said, about the danger that head injuries pose to athletes, especially children.

"I think it's very important that we pay very close attention to that," he said.

The study will be published online Wednesday in the Journal of Neuropathology & Experimental Neurology.

Alan Schwarz of the New York Times contributed to this article. Maura Lerner • 612-673-7384