Friday, July 15, 2016

The controversial second impact syndrome

Loren A. McLendon BS, Stephen F. Kralik MD, Patricia A. Grayson NP and Meredith R. Golomb MD, MSc. The Controversial Second Impact Syndrome: A Review of the Literature.  Pediatric Neurology.  In press.



Second impact syndrome is a devastating injury that primarily affects athletic children and young adults. It occurs when a second concussion occurs before symptoms from the first concussion have resolved. Diffuse and often catastrophic cerebral edema results. Reports of second impact syndrome are few, and some argue that second impact syndrome is simply diffuse cerebral swelling unrelated to the first concussion.


Ovid and PubMed were searched from years 1946 to 2015 using the terms “second impact syndrome,” “repeat concussion,” and “catastrophic brain injury.” In addition, review articles were found using a combination of the terms, “concussion,” “second impact syndrome,” and “repetitive head trauma.”


Seventeen patients in seven publications met the criteria of having two witnessed hits and persistent symptoms from the first to the second concussion. Ten of the 17 (59%) included individuals were football players. All were male. Ages ranged from 13 to 23 years. All children with poor outcomes (death or permanent disability) were younger than 20 years, while four of the five players with good outcomes were older than 19 years. The lag time from first to second concussion ranged from one hour to four weeks, and in many cases, at least one of the two hits appeared minor.


American football, male gender, and young age appear to be associated with second impact syndrome. Controversies surrounding this syndrome are discussed. There is a need for prospective studies to clarify risk factors and outcomes of second impact syndrome to guide return-to-play recommendations for young athletes.

From the article:

There is disagreement about how far apart the two hits can be when considering second impact syndrome. Bey and Ostick  reported that second impact syndrome only occurs when the second hit occurs within a maximum of ten days from the first hit because of the cascade that is disrupted during the first traumatic brain injury.  However, it is possible that children may be at risk for second impact syndrome as long as postconcussive symptoms persist after the first hit.  Some animal work suggests increased susceptibility to neuronal injury when multiple concussions are closely spaced, which might help explain the pathology behind second impact syndrome. An animal study in juvenile rats showed that young rats that received a second concussion one day after the first had more difficulties with recognition tasks and a decreased cerebral metabolic rate of glucose when compared with rats that suffered a second concussion five days later. This suggests that severity of symptoms and cerebral pathology increased when concussions occurred close together.  A longer window between the first and second hits might decrease risk, but further research on this issue is needed...

Most examples of second impact syndrome have been reported in the United States, leading some to question its existence. In 2001, McCrory suggested that second impact syndrome should have been reported in each country if it truly existed. He noted that no examples of second impact syndrome had been diagnosed among Australian football players in spite of less protective equipment, although some did have diffuse cerebral edema on postmortem examination.  However, this may be a result of different rules, fewer players, and lighter weight players. When compared with Australian-rules football, American-rules football allows harder hits and tackles. In the past few years, there have been about 240,000 adult and child regular Australian rules players a year,  compared with 3.5 million U.S. American rules youth football players. In general, Australian-rule football players have had an average body mass index (BMI) around 24.5  while in American football, linemen are often in the obese range with a BMI greater than 30. Australia is now catching up with American obesity rates, and this may increase their risk of second impact syndrome.  Rugby, another game that is popular in many countries, lacks the protective equipment of American football but also tends to have lower force hits and tackles due to a combination of rules and lower BMI players. ..

Another consideration is that athletes tend to underreport head injury. One survey of American college football players found that, for every one head injury the players reported, there were 27 unreported head injuries. Athletes tend to “play through” the discomfort rather than be removed from the game. For offensive linemen, there are 32 unreported head injuries for every one reported.  Now that recognition of second impact syndrome as a possible entity has increased, there are increasing media reports of it outside the United States, including a male teenage rugby player in Ireland   and a female teenage rugby player in Canada.  We did not incorporate these individuals into the analysis because they appeared in the news media, not the medical literature, and the news reports contained few details. The continued overall rarity of well-documented second impact syndrome in the medical literature despite the high number of student athletes and increasing recognition suggests that there must be additional, possibly genetic, risk factors that play a role in this condition.

Several mechanisms for second impact syndrome have been suggested. Bey and Ostick  proposed that diffuse edema after the second hit leads to compression of the parenchyma and vasculature, causing global brain injury. A more widely accepted mechanism is that the brain's vasculature loses its ability to autoregulate after the first traumatic brain injury.  This disruption of autoregulation leads to cerebral edema and engorgement of the vasculature after the second hit because the brain cannot compensate for the edema by decreasing blood flow.  Another suggested mechanism is that shearing forces from the concussion lead to axonal injury, which is then further amplified by multiple mild head blows.  Multiple concussions may cause metabolic disturbances in the brain that make it vulnerable to further injury.  These disturbances include increased metabolism leading to free-radical formation and damage to the neuronal cells.  One marker of high metabolism, N-acetylaspartate, appears to be a possible marker for assessing resolution of concussion.  Metabolic abnormalities after a concussion may leave the brain more susceptible to further injury.  


  1. The two men believe that by its end, the investigation will point to a prime culprit they've been tracking for years, a traumatic brain injury that's very existence is still debated by some scientists, yet one that grows more real with each new casualty – a deadly condition that appears, most cruelly, to prey almost exclusively on young athletes: "second-impact syndrome."

    Its signature is swelling – dramatic swelling, the brain pushing against not just the skull but sometimes down into the spinal column. Most doctors suspect the brain's plumbing breaks, unleashing a flood of blood and fluid, caused – as its name suggests – not by one blow but two: first a malfunction and then a full rupture. The blows can be separated by seconds or by weeks. But much else – from why it occurs to why it seems to strike only young men – remains a mystery…

    Yet for all the uncertainty, one fact seems clear: It is utterly preventable. And that frustrates Dr. Robert Cantu, a leading expert on brain trauma and O'Neil's partner on the project.

    "The same damn thing happens every year, and we're not getting answers," Cantu says…

    Second-impact syndrome would seem an easier fight: Blows too soft to cause concussions can still cause CTE[chronic traumatic encephalopathy], allowing the disease to spread unnoticed for decades – and its connection to football to be denied by coaches, the NFL, the NCAA and youth organizations. Second-impact syndrome, by contrast, appears to require an initial concussion, giving coaches a chance to pull a player – and keep him on the sidelines – before he takes another hit. CTE can't be diagnosed until after death; concussions can be revealed with a quick sideline exam or 30-minute computerized test, which can expose symptoms like headache, nausea or memory loss…

    The pipes that carry blood to the brain – known as arterioles – can expand and contract to regulate blood flow. In second-impact syndrome, however, the arterioles malfunction, dilating and opening a flood that engorges the brain. Among the only treatments is to remove parts of the skull, a strategy that's also used in car crashes. Even then, hope is slim…

    "It's like a leaky faucet, and the water's going everywhere. It's no longer going right out the outlet – it's spraying all over the kitchen," Koroshetz says. "There's no place for the water to go inside the skull, so it just pushes on everything."

    It's a situation that's "often powerless," he says, and "highly fatal."(continued)

  2. (continued)But there seems to be a trend: Many, if not most, victims had suffered a previous concussion – some during that very game, others a few days or few weeks prior but still suffering the symptoms, indicating their brains had not yet healed. In cases where no first impact was apparent, Cantu and O'Neil suspected it may have come during the same game or practice but was masked by the player from his coaches and teammates.

    "These kids are good at hiding it," says O'Neil, whose son, a quarterback at Tufts University, suffered two concussions playing football in high school. "It's another dimension of the whole syndrome: It's really not clinically diagnosable, and if you're good at it and insistent, you can hide the symptoms and stay on the field. And that makes them vulnerable."

    Something seems to break in that second hit, before the brain's had a chance to recover. If that's true, what's unclear is why: the mechanism, that is, that causes the arterioles to malfunction. Nor do doctors know why of the hundreds, if not thousands, of players who surely hide headaches, dizziness and other signs of a concussion from their coaches and trainers every season, only a few suffer second-impact syndrome.

    One survey of college football players from 2014 found that for every head injury an athlete reported, another 27 went unreported. Among offensive linemen, that number rose to 32.

    "There probably are a couple of genetic issues or environmental issues that put a small number of kids at risk, but we don't know what they are," says Dr. Meredith Golomb, associate professor of child neurology at Indiana University School of Medicine.

    Most pressing, neurologists still don't know why only the young seem to succumb to the syndrome…

    What does seem apparent, however, is the danger posed by taking first one hit and then another: It's why, for a condition that's also sometimes known as dysautoregulation or malignant brain edema, so many insist on the term second-impact syndrome.

    "It's telling you that it's preventable. If you had the means to understand that this brain's already been injured, the kid never should be playing," Cantu says. "It implies there's something that can be done about it."…

    Dr. Paul McCrory, a neurologist at the University of Melbourne in Australia, published a paper in 2012 concluding that "scientific evidence to support" the concept of second-impact syndrome is "nonexistent."(continued)

  3. (continued)"It's hard to make guidelines to address it when not all physicians agree it exists," Golomb, of the Indiana University School of Medicine, says. But, she adds, "if you present something new that's frightening, it can be controversial. How many people didn't think smoking caused lung cancer until the evidence became overwhelming?"…

    "I don't think anyone should die from playing football when there's a consistency in the injuries that cause the death," says Andrea Williams, whose 19-year-old brother, Drew, suffered severe brain damage in a game in Chicago in 2013.

    "This level of medical attention is necessary to preserve the game – our children deserve that," she says. "Football adds something to a town, to a high school, to a college. It brings so much goodwill, and the students and the children who are participating and entertaining and drawing crowds are not being paid. They at least deserve the appropriate advocacy and medical attention. We at least owe them that."

  4. The play was a standard corner route: Toran Maronic, rising senior and star receiver of the Bear River High School Bruins, launched up the field, cleats throwing grass and dirt as he cut an angle toward the end zone.

    He'd been getting looks from the nation's top college football programs, letters from premier lacrosse teams – Division I titans with colossal locker rooms and rabid fans and beaming cheerleaders and a path to the pros. A 2-year-old down the block looked to him like a boyfriend, a classmate with autism at Bear River as his best friend, and just about anyone who follows high school sports saw in this teen from just northeast of Sacramento one of the top prospects in the state.

    Thundering toward the far corner on June 24, Toran stretched his arms and dove, reaching for his second touchdown of the game, his fifth in this non-contact weekend tournament. Two spectators standing on the narrow sideline had their backs turned. They were watching a scrimmage on the next field, oblivious as his 180-pound frame sailed toward them.

    Toran slammed into them head-first. Doctors suspect he blacked out before he even hit the ground, his brain smashing against the rough inner surface of his skull. Then it got rocked again, the pivotal blow, when his head, protected by just a soft-shelled helmet, crashed to the turf.

    His father, David, was watching from the sidelines.

    "At first I thought he twisted an ankle or worst-case-scenario broke an arm or leg or something," David says. "And then he just started shaking like crazy, and I took off across the field, and he was in a full seizure and bleeding from the mouth."

    In seconds, Toran, 16, transformed from varsity athlete to trauma victim. Headlines called it a "freak" accident, a terrible injury in a tackle-free tournament. But the outcome was undeniable: Toran, alive yet his brain damaged, was apparently the first boy of the 2016 high school football season to be hurt or killed by head trauma – and still weeks before the official start of preseason camps…

    Toran was among the lucky ones, doctors say. Through hours of speech, physical and occupational therapy, his recovery's outstripped every prognosis. He plans to return to high school this fall to graduate and to return to the field.

    "I'm young so I'm going to play sports again. That's not one of my goals – that's going to happen. I'm going to be on the field on Friday nights again. I'm going to go to college, I'm going to fully recover and I want to repay everyone who's helped me," he says. He ultimately plans to study biology and become a cancer researcher.

    For most others, however, much of what's left is devastation – if not death, long years of rehabilitation and questions of what might have been.