Crosby injury no easy puzzle to solve

Pittsburgh Penguins captain Sidney Crosby has spent more time off the ice than on it in the past year. Sidelined for the bulk of 2011 following a concussion, Crosby returned to play in November in signature fashion, scoring two goals and adding two assists as the Penguins beat the New York Islanders. But by December, Crosby was sidelined again and he hasn't played since.

Crosby has been experiencing symptoms he has described as similar to those he dealt with following last year's concussion, saying he "just didn't feel right" the day after his last game, Dec. 5 against the Boston Bruins.
Crosby has been followed by his medical team in Pittsburgh and has been undergoing physical therapy, making progress along the way, since that time.

However, after Crosby sought an additional opinion last month at the recommendation of his agent, Pat Brisson, there was suddenly much public discussion about what was the actual nature of Crosby's injury. The final consensus from Crosby's medical team and a third independent party, Philadelphia-based spinal surgeon Dr. Alexander Vaccaro, is that Crosby is dealing with a soft-tissue injury in his neck and he is continuing to progress with his rehabilitation efforts.

So why is this injury, which sounds at once benign (soft tissue) and sinister (neck), so difficult to grasp? And why, if it isn't particularly serious, is it proving to be such a hurdle for Crosby to overcome? The answers are simultaneously straightforward and complex.

Some athletic injuries are just easy to comprehend. Take, for instance, the hamstring strain. This is a classic example of a soft-tissue injury (a term typically used to refer to injury of a muscle, tendon or ligament). Hamstring strains can be mild or severe. At best, an athlete might describe nothing more than "tightness" or "pulling," and would recover in a matter of days. In more serious cases, the athlete might feel a "pop" or experience a "tearing" sensation while collapsing in obvious pain. If the athlete was unable to return to play for multiple weeks -- even months -- after such an injury, it might be frustrating but most would understand. And it would not surprise anyone if the biggest concern was whether returning too soon could lead to reinjury.

But when the injury feels less familiar (as is the case with Crosby's) and the soft-tissue injury is located in that no-man's land of the neck (where there are very important things like the spinal cord, discs, nerves and vertebrae), it somehow casts a shadow of a far more serious condition.

The reality is that there are very reasonable comparisons between soft-tissue injuries in any part of the body. Just as a hamstring injury is a soft tissue injury of the thigh, an injury to the muscles, tendons or ligaments of the cervical spine is a soft tissue injury of the neck. Soft tissue, when damaged, bleeds to varying degrees, resulting in pain and inflammation in the injured area, whether it's the thigh or the neck. If a nerve is affected, either by direct injury or as a result of inflammation or muscle spasm around it, it can cause pain, tingling or numbness in the region. In the thigh, a hamstring injury can affect the sciatic nerve. In the neck, any number of nerves can be affected that course through the shoulder, arm or hand. There are many such parallels between soft-tissue injuries in any region of the body.

To be fair, however, the effects of a significant soft-tissue injury in the neck can be slightly more complex, particularly because of the role of mechanoreceptors, sometimes producing symptoms similar to those experienced following a concussion. If that is indeed the case with Crosby, it might explain his challenges in not only sifting through the symptoms but in returning to his sport.

Mechanoreceptors are present in all joint regions of the body and help provide information to the brain about where the body is in space. When a joint moves in such a way that signals it is veering beyond its normal range, the brain can then respond with corrective action to protect the area by stimulating muscle contraction to either brace or reposition the joint, as necessary. Any injury to these mechanoreceptors results in abnormal or inadequate input to the brain about where the joint is in space. Inadequate information leads to an insufficient response and ultimately sets the individual up for further injury. This is one reason returning to play too quickly following an injury results in an aggravation of that injury, often to a more serious degree.

Take the garden-variety ankle sprain as an example, an injury common among weekend warriors and professional athletes alike. When an athlete rolls his ankle and suffers a sprain, ligaments that support the joint can be stretched or torn. Receptors within those ligaments are damaged at the same time. Rehabilitation exercises include range of motion, strengthening of the muscles that support the ankle and, unsurprisingly, balance and agility exercises designed to retrain the ankle to react to directional changes and sport-specific moves in anticipation of returning to play. This balance and agility component is specifically intended to help retrain that input-output loop from mechanoreceptor to brain to a coordinated neuromuscular response. Failure to adequately retrain this system can result in a sensation of instability at the ankle, a factor that could hamper performance or potentially render the athlete more prone to reinjury.

The neck is no different in this regard. The neck, or cervical spine, is made up of the first seven vertebrae beneath the head, all of which are intricately connected by ligaments and supported by muscles, constituting multiple joints. A soft-tissue injury of the neck can yield the same result as a cavalcade of ankle sprains in one concentrated area … only worse. The potential for more problematic symptoms following a neck injury has to do, in part, with the more significant role the mechanoreceptors play in this area. Like their counterparts in the ankle, they contribute to joint stability, but they also play a key role in maintaining posture along with control of head and eye movements. Information from receptors in the neck, especially the upper neck, converges with information from the eyes (visual) and inner ears (vestibular -- balance and equilibrium) so that the body consistently adjusts to being in the right position at the right time, whether moving or standing still.

But what if one of these systems is not functioning properly? Dr. Rob Landel, director of physical therapy and residency programs at the University of Southern California, says this exact scenario creates a "sensory mismatch," which can be extremely debilitating, especially for an athlete. Landel, who has extensive experience in the area of cervicogenic dizziness (or dizziness originating from dysfunction in the neck), says muscular damage in the neck can result in misinformation being sent to the brain about where the head is positioned.

"If you turn your head 10 degrees and your eyes say it's 10 degrees, your ears say it's 10 degrees, but your neck says it's 5 or 15 degrees, then there is a mismatch of information going to the brain," Landel says. "You literally don't know where your head is in space."

He says the symptoms that result are often similar to motion sickness or seasickness, more so than true dizziness. In fact, Landel says when he hears someone describe vague symptoms of feeling "off," "foggy," or like their "head is floating," he immediately suspects the neck as a possible culprit. These symptoms are not unlike postconcussion symptoms, particularly when the vestibular system (the system responsible for how the brain processes motion) is affected. If, like with Crosby, concussion-related tests such as ImPACT are normal, then the neck becomes a more likely source. It is not terribly surprising that there is often overlay between the two because many times in the presence of a head injury the neck has also suffered trauma, often in the form of a whiplash.

Landel points out that injuries involving receptors in the neck can make it difficult to reposition the head in space, track a moving target, maintain balance while holding the head in different positions and contribute to decreased endurance of some of the postural muscles that extend the neck. The demands of hockey require that an athlete be able to perform all of these skills at a high rate of speed while maneuvering around other players on the ice.

"Imagine as a hockey player you're often in a semi-crouched position yet have to keep your head and neck up, track a moving puck and turn your head to varying degrees, all while moving your body at a high rate of speed on a slippery surface," Landel says. "It places an exceptionally high demand on the system."

And just as one might suspect, it takes time to retrain the body to perform these tasks that once seemed so effortless. Each time there is a setback, the recovery process must be revisited in a stepwise fashion, just as Crosby and his medical team are doing now, just as they have been doing since he last played Dec. 5.

Frustration is inevitable, especially for the athlete, since there is no definitive timetable for recovery with these types of injuries, no visible way to measure whether the system has fully repaired itself. The ultimate tests for readiness to return to sport are gradually increasing levels of exertion followed by anxiety-producing waiting periods after exercise to see if symptoms creep back. In a world in which many everyday questions are readily answered via an Internet search engine, often within a fraction of a second, uncertainty and ambiguity often border on the unacceptable. While many looking in from the outside might feel that way, Crosby seems to recognize that such is the nature of these injuries and this latest episode is just another chapter in the story of his career, one that he hopes to turn the page on soon so he can get back to playing hockey.

Although Crosby has shown enough progress to resume skating, he acknowledges he is not yet symptom-free. But as Crosby recently told reporters, "As soon as I am, hopefully I'll be out there. That's where I want to be."

Stephania Bell is a senior writer for ESPN.com, a certified orthopedic clinical specialist and a strength and conditioning specialist.