Of the 10,000 cervical spine injuries that occur annually in the United States, approximately 10% are due to athletic pursuits . Injury to the cervical spine is seen at all levels of competition and in a number of contact and collision sports. The incidence of complete quadriplegia in high school and college football players has ranged from a high of 2.5 per 100,000 in 1976 to 0.5 per 100,000 in 1991 . The rate of transient quadriplegia is more difficult to define as many episodes likely go undiagnosed or unreported.
Transient quadriplegia can be defined as a temporary loss of motor and often sensory function in the arms and legs. The injury is typically seen in athletes following a blow to the head or a whiplash injury. The resulting concussive force to the cervical spinal cord results in a disturbance in nerve transmission that usually lasts for several minutes and then gradually improves. Motor symptoms can range from weakness in the arms and legs to complete paralysis. Sensory symptoms may include numbness, tingling, and burning pain. A survey of over 500 National Collegiate Athletic Association football programs (> 39,000 players) found the incidence of an episode of transient weakness and paresthesias at 1.3 per 10,000 participants and the incidence of an episode of transient paresthesias alone at 6.0 per 10,000 participants [3•].
The on-field management of an athlete who is rendered quadriplegic follows the ABCs of advanced trauma life support care. Establishment and maintenance of an adequate airway is the first priority, followed by assessment and maintenance of breathing and circulation. Full spine precautions should be maintained, including cervical immobilization and log rolling for placement onto a backboard. For football players the facemask should be removed for access to the airway; the helmet can be left in place and taped to the board. If the face mask cannot be removed quickly and immediate access is needed to the airway, one person should stabilize the cervical spine while another removes the helmet. The athlete should be transported to the designated medical center for further evaluation and treatment. Whether to institute the steroid protocol is at the discretion of the treating physician.
When faced with an athlete who has sustained an episode of transient quadriplegia, the physician must do a thorough work-up to rule out bone, disc, or ligamentous injury to the spine. Full neurologic examination should be performed and repeated at regular intervals to document any change. Radiologic evaluation usually begins with cervical spine plain radiographs, including flexion and extension views to rule out ligamentous injury provided no fracture is seen. Computed tomography (CT) scan or polytomography is useful to detect more subtle bony injuries. MRI should be obtained to rule out extrinsic spinal cord or nerve root compression or intrinsic cord abnormalities. Somatosensory evoked potentials may prove useful in some settings to document physiologic cord dysfunction. Any intrinsic abnormalities on MRI or documented by somatosensory evoked potentials provides evidence of cord injury and would preclude return to sports. If the athlete has normal, painless cervical spine movement, normal lordotic cervical spine posture, a normal neurologic examination, and no evidence of bone, disc, or spinal cord injury is seen, return to sport is possible. A second episode of transient quadriplegia should initiate another complete work-up. If all studies are normal a return to competition is not precluded, but the recurrent nature of the problem should raise concern and consideration should be given to limiting further athletic activity.
Whether to allow an athlete who has spinal stenosis to participate in contact and collision sports is a controversial subject that has received increasing attention [4,5•,6•,7–10]. Much of the controversy stems from the lack of a consistent definition of what is meant by spinal stenosis. In 1956 Wolfe et al. [11•] randomly studied 200 subjects with lateral cervical spine radiographs at a fixed distance of 72 inches. Based on these subjects they established normal values for the sagittal diameter of the cervical spine. The canal height, or sagittal diameter, was defined as the anteroposterior (AP) diameter from the posterior aspect of the vertebral body to the most anterior point on the spinolaminal line (Fig. 1). Wolfe et al. [11•] found the average AP diameter was 22 mm at C1, 20 mm at C2, and 17 mm from C3 to C7. General consensus since then has been that from C3 to C7 canal heights greater than 15 mm are normal and spinal stenosis is present when the height is less than 13 mm.
Further attempts to radiographically define spinal stenosis were put forth by Torg et al. [3•] in 1986 and Pavlov et al.  in 1987. They described a ratio of the vertebral canal height divided by the vertebral body, based on the lateral cervical spine radiograph. When this ratio was less than 0.8 they defined it as “significant spinal stenosis.” The main limitation with the ratio method has been a lack of specificity. In one study at the Kerlan Jobe Orthopedic Clinic (Los Angeles, CA), radiographs of 124 professional football players were studied and applying the ratio method 33% had spinal stenosis [13•]. Another study found the positive predictive value of the ratio at 12% . It seems that many professional athletes have normal size spinal canals but larger than normal vertebral bodies, leading to a false diagnosis of spinal stenosis by the ratio method.
A more recent attempt to define stenosis is coined “functional cervical spinal stenosis” [15•,16,17]. This definition is based on MRI study in which a functional reserve of cerebral spinal fluid (CSF) remains around the spinal cord at all levels. Functional cervical spinal stenosis is defined as a cervical spinal canal so small as to obliterate the protective cushion of CSF, or in more extreme cases cause deformation of the spinal cord itself (Fig. 1).
For the athlete who has had an episode of transient quadriplegia and is found to have congenital spinal stenosis by plain film measurement, return to competition is a debated subject. Torg et al.  stated that “although it is controversial, we do not believe that individuals who experience uncomplicated cervical cord neuropraxia are at risk of incurring permanent neurologic sequelae.” This statement is based on their finding that of 45 high school, college, and professional athletes who presented with symptoms of temporary spinal cord concussion, none subsequently became quadriplegic, although not all returned to competition.
Brigham and Adamson  recently presented a case of an athlete with congenital stenosis who did suffer permanent injury. A National Football League (NFL) linebacker presented with a 1-week history of tingling in all four extremities with his neck flexed and MRI confirmed congenital spinal stenosis. Subsequently, while making a tackle, the athlete sustained an axial load to the neck producing numbness in all four extremities and burning dyesthesias in both arms. Postinjury MRI did not reveal any acute injury to disc or bone and repeat MRI 3 months later showed increased signal in the spinal cord and the athlete was advised not to return to collision sports. At 2 years postinjury the athlete still has bilateral upper extremity dyesthesias and mild weakness of the biceps and wrist extensors.
It seems intuitive that a stenotic spinal canal is more prone to injury. Data from the National Center for Catastrophic Sports Injury (Chapel Hill, NC) support this notion . Cases of quadriplegia without cervical fracture have only been seen when functional spinal stenosis is present. For athletes that have suffered quadriplegia due to a fracture or dislocation, the rate of complete neurologic recovery is 0% when cervical stenosis is present compared with 21% when it is not.
Relative Contraindications for Return
For patients that have regained full cervical range of motion, have no pain, and a normal neurologic examination, several relative contraindications exist for return (Table 1). The presence of a healed fracture is a relative contraindication against return, provided there is normal alignment and stability. Cervical disc bulging without frank herniation is a relative but not absolute contraindication. An athlete that has sustained two episodes of transient quadriplegia with no stenosis or underlying anatomic abnormalities should consider discontinuing contact and collision sports.
Absolute Contraindications for Return
An athlete that is still symptomatic or has positive neurologic findings on examination should not return to competition. Similar to athletes symptomatic from a cerebral concussion, those that remain symptomatic from a spinal cord injury are likely more vulnerable to repeat and potentially more serious injury if they return to competition. Athletes with MRI evidence of cervical cord defect or edema should not return. Cervical instability is an absolute contraindication for return. This has been defined as more than 11° of angulation or 3.4 mm translation between two adjacent vertebrae on flexion/extension radiographs. Acute or chronic disc herniation with associated neurologic findings or pain is an absolute contraindication. Upper cervical abnormalities such as os odontodeium, atlanto-occipital fusion, and atlantoaxial instability should preclude further participation. Certain congenital abnormalities such as Klippel-Feil type 1 or type 2 fusions are a contraindication. Degenerative changes such as spear tackler's spine should also prevent return (Table 2).
We now present three cases that illustrate acceptable circumstances as well as relative and absolute contraindications for an athlete to return to contact or collision sports after an episode of transient quadriplegia.
This 27-year-old NFL linebacker experienced transient upper and lower extremity paralysis and numbness after an axial load spear tackle of a 255-pound fullback. Paralysis lasted 4 minutes; during the next 10 to 20 minutes, complete motor and sensory function returned beginning in the lower extremities. On arrival at the hospital, neurologic examination was normal. Cervical spine films showed no evidence of fracture, dislocation or subluxation, or degenerative disc disease. The canal height at all levels measured within normal limits (> 15 mm). There was no evidence of fracture, canal compromise, or contusion on CT or MR imaging, and flexion/extension views of the spine showed no instability.
This is an example of an athlete who has no contraindications for returning to his sport, except for the concern that one episode of transient quadriplegia may make him more likely to have a second than an athlete who has never had these symptoms. This athlete had a complete neurologic recovery and full range of cervical spine movement. The AP diameter of the canal was normal at all levels; CT and MR imaging showed no evidence of functional stenosis. Thus, there were no neurologic, mechanical, symptomatic, or structural (functional spinal stenosis) contraindications for returning to competition. The athlete did return to competition in the NFL and had no further symptoms.
This 23-year-old National Hockey League player was rendered transiently quadriplegic while filming a team advertisement. Bending at the waist with his neck flexed, he unexpectedly collided with another player. The top of the patient's helmet struck the other player's abdomen. Each player had taken one stride prior to impact. The patient had immediate neck pain and felt something was wrong with his arms and legs. He fell to his side and rolled over on the ice onto his back. After 1 minute, he was aware he could move his fingers in his gloves and toes in his skates. A pins and needles sensation extended into both hands and, to a lesser degree, his torso and legs. Within minutes he was aware of a rigid, painful neck; upon moving his head, a shock-like sensation traveled down his spine to his buttocks. After several minutes more, he arose from the ice. Neurologic symptoms persisted at highest intensity for approximately 5 minutes, then gradually subsided first in his legs and then in his arms. It was 2 weeks before all paresthesias had disappeared; at that time the patient had normal range of neck motion and a normal neurologic examination. Plain films showed no evidence of degenerative disc disease, subluxation, or fracture. Spinal canal height exceeded 15 mm at all levels. MRI revealed mild disc bulging at C3-C4, but no spinal cord encroachment. A functional reserve of CSF was present around the cord at all levels. This was confirmed with myelography and contrast-enhanced CT scan.
This is an athlete who has two relative contraindications for returning to play: 1) mild disc bulging at C3-C4, and 2) the fact that the impact that produced the transient quadriplegia seemed relatively minor (head to abdomen impact from one stride apart). Because the myelogram and CT scan did not show functional stenosis and his cervical films were normal, there was not an absolute contraindication to return to play. After consideration of the relative contraindications, this athlete chose not to return to professional hockey.
This athlete first injured his neck as a high school football player making a head-up tackle. He fell to his side unable to get up or roll onto his back. Sensation and motor function were absent from the neck down. Gradually, motor function and sensation returned, first in his feet and then his hands. After several minutes, he was able to stand and walk off the field unassisted, although his legs felt very weak. On the sidelines his neck was rigid and he did not return to play. No radiographic studies were obtained at that time and no medical attention was sought. Three weeks after the injury, because of persistent neck pain and stiffness, he sought medical evaluation at a sports medicine facility, where cervical spine radiographs were taken. Subsequent review of these films revealed canal heights of 12 mm, consistent with spinal stenosis. Two weeks thereafter, the patient returned to competition, his neck pain and stiffness relieved. He played throughout his senior season without cervical symptoms.
The following fall, as a college freshman on full athletic scholarship, he was rendered quadriplegic making a face-to-face and chest-to-chest tackle. Over the next few minutes, movement began to return to his right side and patchy sensation to his left side. Neurologic examination at the hospital revealed a Brown-Sequard syndrome with right-sided hemisensory loss and a nearly flaccid left side. Radiographs, CT scans, and MRIs were obtained. The studies revealed cervical stenosis and posterior disc herniation at C3-C4 with displacement of the cord and thecal sac to the right. Edema was found within the spinal cord from C2 to C5. Surgery was performed without complication, but the patient remained paralyzed immediately afterward. At a second exploration no bleeding was found. The patient went to rehabilitation and remained in a wheelchair for 8 months before walking. He has ultimately recovered to a spastic quadriparetic state.
This is an example of an athlete with an absolute contraindication for return to competition. In addition to a stenotic canal with an AP diameter of 12 mm, he had functional stenosis on CT and MRIs with cord displacement and edema secondary to disc herniation. Because studies were not performed following his initial injury, it is not known whether he had cord displacement at that time, but the stenosis was present. This finding should have prompted further evaluation with MRI, myelogram, or contrast-enhanced CT scan, and the likely presence of functional spinal stenosis should have terminated his football career after his initial episode of transient quadriplegia. If he had not had severe spinal stenosis, it is probable that the disc herniation would have produced radicular symptoms alone instead of severe spinal cord injury.
All three athletes suffered a bout of transient quadriplegia. Although such an event may occur following hyperextension or hyperflexion, it most frequently occurs with an axial load injury to the cervical spine, as described by Torg et al. . In all three cases presented here, the symptoms were consistent with variations of the cervical spinal cord syndrome as described by Schneider et al. .
Cervical spinal stenosis is known to increase the risk of permanent neurologic injury. Firooznia et al.  presented the case reports of three patients who became quadriplegic after only minor trauma. Radiologic studies of all three patients showed marked stenosis of the spinal canal. Resnick  stated that CT and myelography are the most sensitive modalities in determining spinal stenosis. He pointed out that plain radiographs fail to appraise the width of the cord and are not useful when stenosis results from ligamentous hypertrophy or discal protrusion. Ladd and Scranton  reported that the AP diameter of the spinal canal is unimportant if there is total impedance of the contrast medium. They argued that a metrizamide-enhanced myelogram is needed in the injured athlete because CT alone fails to adequately reveal dural compression. Perhaps the best study to identify spinal stenosis, especially functional stenosis with loss of the CSF cushion, is MRI. In one study of 11 athletes rendered quadriplegic, MRI revealed six patients had functional spinal stenosis.
Mechanism of injury is a factor in deciding whether to allow an athlete to return to participation after an episode of transient quadriplegia. Eismont et al.  stated that athletes with cervical stenosis are remarkably susceptible to hyperextension injuries known to produce maximal narrowing (up to 2 mm) of the ventrodorsal diameter of the spinal cord. Torg et al. [3•] noted that hyperextension causes an inward indentation of the ligamentum flavum that can compress the cord. Penning  described a “bony pincers” mechanism in hyperextension in which the cord is compressed between the vertebral body and the closest portion of the spinolaminar line of the inferior vertebra. The patient in Case 3 appeared to suffer a hyperextension injury, making contact with the face mask, and it was spinal stenosis that predisposed him to neurologic injury. The athletes in Case 1 and Case 2 sustained an axial load injury leading to transient quadriplegia. In Case 1 the force was severe enough to dent the athlete's helmet. It was likely that this tremendous impact, rather than any underlying predisposition caused the transient injury, and therefore return to competition was allowed. In Case 2 the force of the blow was not great; however, the contact was not expected and therefore the athlete's neck muscles were relaxed, causing greater transmission of the forces directly onto the spine instead of being dissipated in the muscles. In general, a relatively minor impact that results in transient quadriplegia should raise concern about underlying anatomic abnormality and may be a reason to limit further participation in contact and collision sports.
The three athletes discussed here present a spectrum of when to allow return to competition in contact and collision sports following an episode of transient quadriplegia. It is important to realize that a normal canal size on lateral radiographs does not preclude the possibility of functional spinal stenosis as an absolute contraindication for return to the sport. For this diagnosis contrast-enhanced CT scan or MRI is needed. It is also important to realize that given the infrequent nature of this injury, prospective studies are limited. It is likely that a type II or beta error is present in studies failing to show increased rates of further injury in athletes with anatomic abnormalities, such as stenosis, that return to competition after an episode of transient quadriplegia. Ultimately the recommendations presented here are guidelines and each case should be dealt with on an individual basis.
Participation in contact and collision sports carries inherent risks. Given the popularity of these sports, it is important to try to minimize the more serious injuries that can occur. Transient quadriplegia is an injury that merits aggressive evaluation for underlying structural abnormalities that could cause permanent injury if the athlete returns to competition. Return-to-play decisions are not always clear cut and often require individualization. This article has provided a framework for these decisions. Athletic injury with permanent neurologic impairment precludes the player from further participation in contact sports. Injuries causing transient neurologic disturbance with normal radiographic studies and no evidence of injury on complete work-up would not preclude return to competition once the athlete is symptom free. Athletes with significant bony or ligamentous spinal instability, spinal cord contusion, or functional stenosis are advised not to return to contact sports. Other radiographic abnormalities such as spear-tackler's spine, posterior ligamentous injury, congenital fusion, herniated disc, or degenerative spondylotic disease require consideration on an individual basis.
References and Recommended Reading
Papers of particular interest, published recently, have been highlighted as: • Of importance, •• Of major importance
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Article that presented the Torg ratio of spinal stenosis.
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5.• Vaccaro AR, Klein GR, Ciccoti M, et al.
: Return to play criteria for the athlete with cervical spine injuries resulting in stinger and transient quadriplegia/paresis. Spine J
Review of return-to-play criteria after cervical injury.
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Recent article summarizing the return-to-play considerations after transient quadriplegia.
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: The relationship of developmental narrowing of the cervical spinal canal to reversible and irreversible injury of the cervical spinal cord in football players. An epidemiological study. J Bone Joint Surg Am
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Original article defining cervical stenosis based on radiographs.
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: Incidence of cervical spinal stenosis in professional and rookie football players. Am J Sports Med
Article demonstrating lack of specificity Torg ratio in NFL athletes.
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: Normal cervical spine morphometry and cervical spinal stenosis in asymptomatic professional football players. Spine
15.• Cantu RC: Functional cervical spinal stenosis: a contraindication to participation in contact sports. Med Sci Sports Exerc
Article defining functional cervical spinal stenosis.
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22. Resnick D: Diagnosis of bone and joint disorders.
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24. Eismont FJ, Clifford S, Goldberg M, et al.
: Cervical sagittal spinal canal size in spinal injury. Spine
25. Penning L: Some aspects of plain radiography of the cerebral spine in chronic myelopathy. Neurology