There’s no escaping the stream of headlines this football season about the effects of repeated concussions on the long-term mental health and mental function of football players. While the concerns behind those headlines focus on concussions involving brain injury, they’re only part of the concussion story in football. Less attention is paid to concussion to the spinal cord — known medically as cervical cord neurapraxia (CCN) — even though CCN has been recognized as a threat of particular concern among football players for over 25 years.
Concussion to the spinal cord
Most cases of CCN occur on the football field and result from severe head collisions where a player’s neck is either compressed or bent far backward or forward with great force. Players in positions that involve high-speed collisions and open-field tackling, like free safety, are most commonly affected.
CCN involves a transient injury to the spinal cord that causes brief disturbance of sensation and/or the ability to move. Symptoms can include numbness and tingling in the hands or feet as well as weakness or even brief complete paralysis. Affected areas can range from a single arm or leg to all four limbs. Episodes last less than 24 hours and often for just a few seconds, after which the individual returns to how he was before the injury.
What You See: A 25-year-old pro football player who had several episodes of leg weakness and unsteady gait after head-on collisions. On the left is an X-ray of his neck showing reversal of the upper spine’s normal protective curvature, resulting in overcurvature. In the middle is an MRI showing a spinal disc herniation with narrowing of the spinal canal. Such narrowing is associated with increased risk of another episode of cervical cord neurapraxia (CCN). On the right is a postoperative X-ray after the player underwent a two-level spinal fusion that eliminated the disc herniation and spinal cord compression. He did not return to football and hasn’t suffered any more leg or walking abnormalities.
The unlikely source of CCN risk
Studies indicate that CCN occurs in about seven out of every 10,000 football players. That doesn’t sound like much until you consider that 1.8 million Americans play football, including 1.5 million junior and senior high school students.
Interestingly, the risk of CCN can be traced to an unlikely source: the modern football helmet. Before the modern helmet emerged in the 1960s, bleeding within the brain from head trauma was the leading head and neck injury in football, explains Gordon Bell, MD, Director of the Center for Spine Health at Cleveland Clinic. After the modern helmet appeared, he adds, bleeding rates fell sharply while rates of CCN, spine fracture/dislocation and quadriplegia soared.
“Paradoxically, the modern helmet’s superior protection of the head and brain promoted playing techniques that put the neck at risk for injury,” says Dr. Bell.
Why spearing was squelched
A chief culprit was “spearing,” the tackling technique of lowering the head and hitting an opponent with the crown of the helmet. “Lowering the head even slightly reverses the spine’s normal curvature,” says Dr. Bell. “This results in a straightened spine that can’t properly absorb the force applied in a collision. Fracture of the vertebrae that surround the spinal cord can result, with possible spinal cord injury.”
As spearing’s effects became better understood, the technique was banned from all levels of football in the 1970s, and rates of quadriplegia and less serious spine injuries in football fell substantially. Rates of CCN likely fell as well, although CCN was not formally recognized until the mid-1980s.
How size matters when it comes to CCN
Yet CCN continues to occur in hundreds, if not thousands, of football players a year, so what should we make of it?
“The long-term effect of one or more episodes of CCN on spinal cord function is unknown,” says Dr. Bell. “Only recently have we begun to appreciate the long-term effect of multiple concussions on brain function. So it seems there’s potential for long-term effects following multiple episodes of CCN.”
The issue of repeat episodes of CCN seems to be key, as about half of all football players who suffer an episode of CCN who return to play will experience a second episode. The risk of a repeat episode is directly related to the diameter of a player’s cervical spinal canal, or the tube formed by the vertebrae in which the spinal cord and its membranes are located in the upper (neck) part of the spine.
“The smaller the spinal canal, the higher the risk of repeat CCN,” says Dr. Bell.
To return to play or not?
For that reason, spinal canal width (which can be determined by MRI) is a key factor considered by doctors when they advise football players whether it’s safe to return to play after a CCN episode.
Dr. Bell says there are no clear guidelines for making these return-to-play decisions, but it’s generally thought that return to play is allowable after a single episode of CCN in a player with normal results on neurologic tests, normal spinal alignment and a normal spinal canal diameter with no evidence of spinal cord compression.
There’s also general agreement that players should not return to football or other collision sports if they have:
- Any lasting neurologic effects or symptoms or any persistent spinal cord damage
- A history of multiple episodes of CCN
- An unhealed spinal fracture or spine instability
- Conditions such as myelomalacia of the spinal cord (which suggests bruising of the spinal cord) or certain congenital abnormalities of the spine
Most controversial is the case of a player who’s suffered a single episode of CCN and has evidence of narrowing of the spinal canal with spinal cord compression. While erring on the side of caution may be easier for players at the recreational or high school level, the call can be tougher at the college or professional levels, where scholarships and financial considerations typically figure in.
Even so, Dr. Bell says he’d be “very reluctant” to give return-to-play clearance following an episode of CCN in an athlete who has significant reduction in spinal canal diameter associated with a reduction or elimination of the cushion of cerebrospinal fluid surrounding the spinal canal. “This can increase the risk of permanent spinal cord injury in the event of another neck injury,” he explains.
For some players who insist on returning to competition, surgery can occasionally reduce the risk of repeat CCN and permanent cord injury, he adds.
Dr. Bell notes that the best defense against CCN in football is for coaches and trainers to stress the importance of proper tackling technique, with the head kept up, and for referees and all observers to show zero tolerance for spearing.