Neurapraxia, "stingers," and spinal stenosis in athletes.

Research into the mechanisms of cervical injury in football have led to rule changes, such as the ban on spearing, that in turn have led to a substantial drop in the number of catastrophic cervical spine injuries. Improvements in the coaching of tackling techniques and protocols for field management of cervical injuries have also contributed to increased safety. Despite the decrease in catastrophic events, cervical injuries such as sprains, "stingers," and neurapraxic events, remain prevalent, and present some of the most challenging diagnostic and management problems encountered in the care of athletes.

Cervical Cord Neurapraxia 

Torg et al (1) first described in 32 athletes the syndrome of cervical cord neurapraxia with transient quadriplegia. The symptoms include acute bilateral burning pain, tingling, and loss of sensation involving the upper and lower extremities. Associated motor symptoms vary from weakness to complete paralysis. Neck pain and loss of cervical motion are not experienced at the time of injury. The episodes are transient, with complete recovery usually within minutes, although some patients have gradual recovery that may take up to 48 hours. Radiographs are negative for acute fracture or dislocation. The initial study as well as follow-up reports showed no predisposition in these patients to permanent neurologic damage. (2)

Review of the radiographs in this population demonstrated narrowing of the cervical canal compared to a group of asymptomatic controls. The narrowing was developmental or secondary to degenerative, congenital, or posttraumatic changes. They concluded that this cervical stenosis was the factor that explains the appearance of spinal cord neurapraxia. (2) Forced hyperflexion or hyperextension in a stenotic canal causes additional narrowing and compression of the spinal cord by the pincers mechanism described by Penning. (3) The spinal cord is momentarily pinched between the posteroinferior margin of the superior vertebral body and the anterosuperior lamina of the subjacent vertebra.

The diameter of the spinal canal is assessed on the lateral radiograph by measuring the distance from the posterior aspect of the vertebral body to the most anterior margin of the spinolaminar line. Measurement of this diameter is often inaccurate due to variations in magnification secondary to differences in patient size, target distance, and placement of the film. Torg and Palov (4) proposed that the ratio of canal diameter to vertebral body width is a more reliable method to determine cervical spine stenosis (Fig. 1). This ratio is independent of variations in technique, as both the canal and vertebral body are in the same plane and similarly affected by differences in magnification. The ratio in their asymptomatic controls was one to one. They determined that a ratio of less than 0.8 indicated significant cervical stenosis.

Subsequent studies raised concern about the accuracy of the Torg ratio in identifying football and other types of athletes with significant cervical stenosis. Odor et al (5) observed that one third of asymptomatic professional football players had a Torg ratio of less then 0.8 at one or more levels. Herzog et al (6) found an abnormal Torg ratio in 49% of the professional football players they studied. They determined that Torg ratio was often inaccurate in detecting stenosis because it is influenced by the size of the vertebral bodies. The vertebral bodies of the football players in their study were significantly larger than the controls in Torg's study and artificially lowered the Torg ratio.

Torg reevaluated the population of patients with cervical cord neurapraxia and compared them to a group of asymptomatic college and professional football players. This study again demonstrated a large percentage of asymptomatic athletes with a Torg ratio less than 0.8. Because of the low incidence of cervical cord neurapraxia (7.3 per 10,000 athletes), the positive predictive value of a Torg ratio less than 0.8 for developing cervical cord neurapraxia was 0.2%. It was concluded that the Torg ratio was not a useful screening method for predicting cervical cord neurapraxic events and determining suitability for participation in contact sports. (1)

The management of athletes who have episodes of cervical cord neurapraxia is controversial. The rate of recurrence of episodes of neurapraxia in athletes who return to football is 56%. Torg recommended a relative contraindication to return to play for athletes who experience an episode of cervical cord neurapraxia and have a Torg ratio less than 0.8 or degenerative changes or evidence on magnetic resonance imaging (MRI) of cord deformation. Absolute contraindications include a single neurapraxic event with evidence of cord damage or ligamentous instability, multiple episodes, or episodes with symptoms lasting greater than 36 hours. (7)

Cantu (8) reported one episode of quadriplegia in an athlete with a previous episode of cervical cord neurapraxia. This has led some authors to recommend excluding players from return to contact sport participation after any episode of cervical cord neurapraxia. (9)

"Stingers"

Although screening has not been predictive for central cord neurapraxia, it may be useful in more common conditions. "Stingers" are the most frequent cervical spine-related injury in football. Incidence of stingers has been reported to be 7.7% per year (10) and as high as 65% during a player's career. (11) Stingers (or burners), are a neurapraxia of the brachial plexus or cervical nerve roots. Stingers are characterized by pain and paresthesias in a single upper extremity. Athletes experience burning and tingling radiating from the neck to the shoulder, arm, and hand. The pattern is not dermatomal. (12) Concomitant weakness of deltoid, supraspinatus, and biceps may be present. Symptoms are usually transient with pain resolving in a few minutes. Weakness, when present, resolves within 24 hours. (13) In some cases, weakness may be prolonged for weeks. (14)

Two main mechanisms of stingers have been described. The first mechanism involves depression of the shoulder and lateral neck bend away from the side of injury. This is commonly seen with a block or tackle in football, but occurs in other sports. This causes a traction injury on the upper trunk of the brachial plexus. Traction injuries are not typically associated with neck pain or loss of cervical motion. (15)

Another mechanism involves neck extension and rotation, or lateral bend towards the symptomatic side. This causes narrowing of the foramen and compression of the nerve root(s) on the symptomatic side, similar to the Spurling maneuver. These athletes frequently have neck pain. Extension-compression stingers usually occur in relatively older athletes and are more likely to be problematic or persistent. (15) Meyer (16) reported that 85% of the players with problematic stingers had an extension-compression mechanism. Average time lost for extension-compression stingers was 12.3 days versus 1.5 days for brachial plexus stretch stingers. A review of athletes with chronic burner (stinger) syndrome by Levitz et al (17) documented an extension-compression mechanism in 83% and associated disc disease or degenerative changes in 94%. They concluded that chronic burners are most commonly caused by nerve root compression.

[FIGURE 1 OMITTED]

Athletes who experience stingers may return to play if symptoms resolve quickly and they have full painless motion of the neck, and complete recovery of strength. Relative contraindications to return to play include stinger symptoms prolonged for more than 24 hours, or multiple episodes. These patients should be thoroughly evaluated, including appropriate imaging studies to diagnose underlying pathology. Absolute contraindications to return to participation include persistent neck pain, loss of motion, neurologic deficit, or evidence of cervical myelopathy. (18)

Stingers and Spinal Stenosis 

Cervical stenosis has been associated with a higher incidence of stingers caused by cervical root compression. Meyer reported that 47% of athletes with stingers had a Torg ratio less than 0.8 at one or more levels versus 25% of asymptomatic athletes. Players with a Torg ratio less than 0.8 were three times more likely to have a stinger. Meyer and his coauthors proposed that players with narrow canals would have short pedicles and associated narrowed foramina, predisposing them to nerve root compression. (16) Levitz reported that 53% of patients with chronic burner syndrome had narrowed canals. (17) Kelly et al (19) described a method of assessing foraminal stenosis with a foramen/vertebral body ratio on oblique radiographs. They reported a higher incidence of both cervical and foraminal stenosis in players with burners.

Controversy persists regarding the usefulness of evaluating cervical stenosis as a predictor of stinger experience. Castro et al (10) did not establish a relationship between Torg ratio and initial stinger experience in their review of 165 athletes. While a relationship between stenosis and stingers may exist, certainly many athletes with stenosis never experience stingers. Meyer et al discussed the possibility of using prophylactic equipment, such as a neck collar or more protective shoulder pads, in athletes identified as having cervical stenosis. They cited concerns regarding the cost/benefit ratio and probable compliance with this approach. (16)

In addition, the question of the accuracy of radiographs and the Torg ratio in screening for cervical stenosis applies to this population as well. Castro et al stated that the reportedly high prevalence of cervical stenosis in asymptomatic football players is a misinterpretation of Torg's original definition. These studies labeled athletes as stenotic if they had a Torg ratio less than 0.8 at any level. Castro stated that the threshold level for significant stenosis is an average Torg ratio of less than 0.8 over the entire spinal canal. They recommended a more appropriate threshold for significant stenosis at any level is a Torg ratio less than 0.7. (10)

We reviewed our experience with preparticipation screening radiographs for cervical stenosis at the University of South Carolina. The Torg ratio was measured on 125 football players screening lateral cervical spine radiographs. Players with subsequent cervical spine-related injuries over a three year period were identified and the accuracy of the screening Torg ratio in predicting these injuries was evaluated. There were no players with cervical cord neurapraxia. Fourteen players (11%) developed stingers that resulted in time lost from practice or games. Forty-six players (37%) had a Torg ratio less then 0.8 at one or more levels. Players with a Torg ratio less than 0.8 were four times more likely to experience a stinger. The sensitivity and specificity of a Torg ratio less than 0.8 predicting stinger experience was 71% and 68%, respectively. The positive predictive value of a Torg ratio less than 0.8 for predicting stinger experience was 22%. The average vertebral body size was much larger than the control group in Torg's original cervical neurapraxia study (20.4 mm versus 19.1 mm).

Based on these results, we concluded that the Torg ratio was not accurate in predicting neurapraxia or stinger experience, and was not useful in directing clinical decision making for asymptomatic players. We have discontinued routine screening cervical spine radiographs for incoming players. Current indications for lateral cervical spine radiographs at the University of South Carolina include history of cervical-related injuries in incoming players, cervical sprains, prolonged stinger deficit, multiple stingers, and cervical neurapraxia.

The above discussion is in detail since the area of cervical spine injury is very controversial and multispecialty related. Trainers, orthopaedists and primary care physicians, or even other specialties or emergency medical service personnel can be first responders.

Neurosurgeons and additional subspecialty providers all might help with decision making. The final decision frequently is that of the athlete and family.

Music is the only language in which you cannot say a mean or sarcastic
thing.
--John Erskine

Table 1. Symptoms of spine injuries

Cervical cord neurapraxia (a)
  Acute bilateral burning pain
  Tingling
  Loss of sensation in upper and lower extremities
  Weakness to complete paralysis
  Transient
"Stingers"
  Pain and paresthesias in single upper extremity
  Burning and tingling radiating from the neck to shoulder, arm, hand
  Possible concomitant weakness of deltoid, supraspinatus, biceps
  Transient

(a) Radiographs negative for acute fracture or dislocation.

Table 2. Management of spine injuries: absolute contraindications for
return to play

Cervical cord neurapraxia
  Single neurapraxic event with evidence of cord damage
  Ligamentous instability
  Multiple episodes
  Episodes with symptoms lasting more than 36 hours
"Stingers"
  Persistent neck pain
  Loss of motion
  Neurologic deficit
  Evidence of cervical myelopathy

Principles and Guidelines

1.  All neck injuries are to be considered serious until proven
    otherwise.
2.  Cervical spine stenosis is associated with a higher incidence of
    cervical cord neurapraxia and stingers.
3.  Cervical spine stenosis in an asymptomatic player is not a
    contraindication for participation in contact sports.
4.  Return to contact sport after cervical injury at secondary, college,
    or professional level requires decisions involving several
    disciplines as well as the athlete and family.

Fig. 2 Principles and guidelines for response to cervical injuries in
athletes.

Accepted May 21, 2004.

References

1. Torg JS, Naranja RJ Jr, Palov H, et al. The relationship of developmental narrowing of the cervical spine to reversible and irreversible injury of the cervical spinal cord in football players. J Bone Joint Surg Am 1996;78-A:1308-1314

2. Torg JS, Palov H, Genuario SE, Sennett B, et al. Neurapraxia of the cervical spinal cord with transient quadriplegia. J Bone Joint Surg Am 1986;68-A:1354-1370

3. Penning L. Some aspects of plain radiography of the cervical spine in chronic myelopathy. Neurology 1962;12:513-519.

4. Palov H, Torg JS, Robie B, et al. Cervical spinal stenosis: determination with vertebral body ratio method. Radiology 1987;164:771-775.

5. Odor JM, Watkins RG, Dillin WH, et al. Incidence of cervical spinal stenosis in professional and rookie football players. Am J Sports Med 1990;18:507-509.

6. Herzog RJ, Wiens JJ, Dillingham MF, et al. Normal cervical spine morphometry and cervical spine stenosis in asymptomatic professional football players. Spine 1991;16(Suppl 6):S178-S186.

7. Torg JS, Corocoran TA, Thibault LE, et al. Cervical cord neurapraxia: classification, pathomechanics, morbidity, and management guidelines. J Neurosurg 1997;87:843-850.

8. Cantu RC. Cervical spine injuries in the athlete. Semin Neurol 2000;20:173-178.

9. Castro FP. Stingers, cervical cord neurapraxia, and stenosis. Clinics in Sports Med 2003;22:483-492.

10. Castro FP. Stingers, the Torg ratio, and the cervical spine. Am J Sports Med 1997;25:603-608.

11. Sallis RE, Jones K, Knopp W. Burners: offensive strategy in an underreported injury. Phys and Sports Med 1992;20:47-55.

12. Hershman EB. Brachial plexus injuries. Clin Sports Med 1990;9:311-329.

13. Clancy WG, Brand RL, Bergfeld JA. Upper trunk brachial plexus injuries in contact sports. Am J Sports Med 1977;5:209-216.

14. Speer KP, Bassett FH III. The prolonged burner syndrome. Am J Sports Med 1990;18:591-594.

15. Kelly JD. Brachial plexus injuries: evaluating and treating "burners". J Musculoskel Med 1997;14:70-80.

16. Meyer SA, Schulte KR, Callaghan JJ, et al. Cervical spinal stenosis and stingers in collegiate football players. Am J Sports Med 1994;22:158-166.

17. Levitz CL, Reilly PJ, Torg JS. The pathomechanics of chronic, recurrent cervical root neurapraxia. The chronic burner syndrome. Am J Sports Med 1997;25:73-76.

18. Vaccaro AR, et al. Cervical spine injuries in athletes: current return-to-play criteria. Orthopedics 2001;24:699-703.

19. Kelly JD, Aliquo D, Sitler MR, et al. Association of burners with cervical canal and foraminal stenosis. Am J Sports Med 2000; 28(2):214-7

Steve Page, MD, and Jeffrey A. Guy, MD

From the Department of Orthopaedic Surgery, University of South Carolina School of Medicine, Columbia, SC.

Reprint requests to Jeffrey A. Guy, MD, Two Medical Park, Suite 404, Columbia, SC 29203.