Expert Opinion and Controversies in Musculoskeletal and Sports Medicine: Stingers

Article Outline

• Abstract
• Controversies
  • The Site of Injury
  • Diagnostic Evaluation
  • Return-to-Play
• Practical Approaches
  • Where is the Site of Injury?
  • How Do I Evaluate the Athlete With an Acute Stinger on the Field?
  • When Do I Need to Obtain Imaging and, if So, What Type?
  • What is the Role of EDX?
  • What About Longer-Term RTP Considerations for an Athlete With Recurrent Stingers or Persisting Neurological Deficits?
  • Is There a Role for Equipment Modifications in the Prevention of Recurrent Stingers?
• Conclusions
• References
• Copyright

Abstract 

Standaert CJ, Herring SA. Expert opinion and controversies in musculoskeletal and sports medicine: stingers.

Stingers are a common injury in contact sports and are characterized by acute lancinating pain in 1 upper extremity with or without associated weakness and neck pain. Appropriate on-field evaluation is necessary to identify the extent of injury and rule out structural injuries to the head, spine, or shoulder girdle. Although athletes can often return to play after a single acute event that resolves rapidly, those who have recurrent events, persisting pain, or strength deficits require a thorough diagnostic evaluation before return-to-play decisions can be made. In some circumstances, players sustaining a single stinger or multiple recurrent stingers may be permanently removed from participation in collision or contact sports.

Key Words: Neck pain, Radiculopathy, cervical, Brachial plexus, Sports medicine, Rehabilitation

List of Abbreviations: CT, computed tomography, EDX, electrodiagnostic studies/electrodiagnosis, MRI, magnetic resonance imaging, ROM, range of motion, RTP, return-to-play

STINGERS MAY BE THE MOST common upper extremity nerve injury seen in competitive athletes.¹, ² A stinger, also known as a “burner,” is classically thought of as a transient episode of shooting or electrical pain or paresthesias radiating down 1 upper extremity after an acute event, typically one involving significant contact to the head and/or shoulder.³, ⁴, ⁵ The pain or sensory symptoms can be accompanied by varying degrees of weakness. Although the symptoms usually resolve spontaneously in a short amount of time, stingers can result in permanent neurological deficits or become a recurrent problem that may ultimately limit an athlete's ability to continue to play collision or contact sports. Stingers have been reported to occur in up to 50%–65% of collegiate football players over the course of their career, and recurrence rates can be high.⁵ There are a number of diagnostic and treatment options that can be considered for athletes with persisting or recurrent symptoms, although there is a distinct lack of guidelines regarding treatment, prevention, and RTP.

The pathophysiology of stingers remains unclear. Several mechanisms of injury have been proposed, predominantly falling into either tensile or compressive categories.⁶ Tensile injuries may result from traction to either a cervical nerve root or the brachial plexus due to rapid lateral flexion of the neck to the contralateral side of the injury and/or depression of the ipsilateral shoulder. Compressive mechanisms may include injury to the nerve root in the neural foramen caused by rapid extension and lateral flexion to the ipsilateral side of symptoms or direct compression of the brachial plexus.⁴, ⁵, ⁶, ⁷ There is disagreement as to the exact location of injury (ie, cervical root vs brachial plexus), and it may well be difficult to sort this out in many cases.² There may be a number of specific factors predisposing a given athlete to stingers, including equipment and technique issues, and researchers have identified high rates of structural abnormalities in the cervical spine in athletes with recurrent stingers, particularly spinal canal or neural foraminal stenosis.⁴, ⁵ Stingers are associated with unilateral symptoms, and the presence of bilateral upper extremity symptoms after sports trauma should raise concern for a spinal cord process, requiring a very different approach to assessment and management.

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Controversies 

The Site of Injury 

There is disagreement between authors as to the relevant site of neurologic injury in a stinger. They may represent either nerve root or plexus injuries, and there may be a different distribution of the relative proportions of cervical vs plexus injuries in different age groups. Some authors have suggested that traction to the brachial plexus may be more common in younger athletes while nerve root compression in the neural foramen is more common in older collegiate and professional athletes.⁵

Diagnostic Evaluation 

The indications for spinal imaging in athletes with stingers are not clearly defined. Plain radiographs, flexion/extension views, MRI, and CT with or without myelography may all potentially be useful. EDX may also be helpful in the setting of persisting weakness. The implications of imaging findings are also not always clear, given some of the distinct anatomical and radiographic features associated with high level sports participation. These can range from increased bony and diskogenic abnormalities in the thoracolumbar spine in young athletes to a relatively increased size of the cervical vertebral bodies in professional football players when these athletes are compared with the general population.⁸, ⁹

Return-to-Play 

Decisions need to be made about RTP both within the same game and in subsequent games after a stinger. There is no uniformly agreed-upon limit as to how many stingers a given athlete can safely sustain within a season or a career nor of the precise clinical or diagnostic criteria necessary for decisions about continued sports participation. A variety of diagnostic methods may be helpful in making longer-term decisions.

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Practical Approaches 

Where is the Site of Injury? 

The injury location may vary between athletes. In their study of 190 athletes with peripheral nerve injuries identified on EDX, Krivickas and Wilbourn² identified stingers (or “burners”) in 38. The abnormalities were generally consistent with either C5 or C6 root pathology or an injury to the upper trunk of the brachial plexus. They noted that in most of the cases it was difficult to definitively localize the injury specifically to either a root or the plexus. In a study of 55 athletes with recurrent stingers, Levitz et al⁵ found that the mechanism of injury in 83% involved cervical extension combined with lateral deviation to the symptomatic side, most consistent with a compressive injury to the nerve root in the spine. These athletes were predominantly at the professional or intercollegiate level (mean age of 23), and 93% had disk disease or foraminal narrowing on imaging. The authors felt that these findings suggested a predominance of root-level injuries in intercollegiate or professional athletes. Meyer et al¹⁰ noted similar findings suggestive of a predominantly cervical origin for stingers in their series of collegiate football players. Conversely, other authors have described a predominance of brachial plexus injuries in their case series of stingers that included EDX evaluation.¹¹, ¹², ¹³, ¹⁴

From an anatomic perspective, the cervical nerve roots would seem to be more vulnerable than the plexus to either traction or compression. A number of features make the brachial plexus more resilient to injury, including its plexiform structure and the amount of perineural tissue in the plexus compared with the roots.⁶ The orientation and structure of the cervical roots leaves them more vulnerable to injury, particularly the anterior rootlet, which may account for what clinically seems to be a predominance of motor deficits seen in persistent stingers.⁶

How Do I Evaluate the Athlete With an Acute Stinger on the Field? 

The first step in the acute evaluation of an athlete with a suspected stinger is to ensure that there is no indication of an injury to the spinal cord or brain. Any association of arm pain with headache or altered mental status, or the occurrence of symptoms extending into other extremities should immediately raise concern for a central nervous system injury. The presence of significant neck pain, decreased cervical range of motion, and/or neurological symptoms or pain affecting more than 1 extremity should also raise concern for a cervical spine injury. In these settings, appropriate spine precautions need to be maintained.

Once it is established that the symptoms are isolated to 1 upper extremity with an otherwise normal neurologic status, a more focused exam of the affected limb should be undertaken. The cervical spine, shoulder girdle, and upper limb should be evaluated to exclude an underlying fracture or dislocation as a cause of the neurologic symptoms. Pulses should be checked to ensure there is no concurrent vascular injury. A neurologic examination of the affected upper extremity should be done, including the testing of strength and sensation. Given the predominance of injuries to the C5/C6 roots and the upper trunk of the brachial plexus, particular attention should be paid to motor function served by this distribution, such as elbow flexion, shoulder abduction, and shoulder external rotation. If the symptoms resolve rapidly (seconds to a few minutes), and the athlete is neurovascularly intact, has full cervical and shoulder ROM without pain, and Spurling's test is negative, consideration can be given to returning the athlete to play in the same game (table 1). If the event in question is not the athlete's first stinger of the season or if the athlete has suffered recurrent stingers, strong consideration should be given to withholding the athlete from RTP in the same game. This may be a particularly important consideration in the setting of more severe stingers or those occurring closely together. If there is any question about a persisting neurologic deficit or if there are any deficits in cervical ROM, the athlete should not RTP that game. For athletes with an identified neurological deficit, serial examinations should be performed on the field and, subsequently, in the office over the ensuing days if they persist. Neurologic deterioration should prompt rapid evaluation of the cervical spine, head, or plexus as indicated.

Table 1. Return-to-Play After Stingers in the Amateur Athlete

Generalreturn-to-playcriteria

Adequatetimetohealfromprimaryinjury

Absenceofunderlyingconditionsthatposeundueriskoffurtherinjury

Resolutionofallsymptoms

Full,pain-freeROM

Appropriatecardiovascularfitness

Normalstrength

Abilitytoperformsport-specificskillswithoutsymptoms

When Do I Need to Obtain Imaging and, if So, What Type? 

Not every athlete sustaining a stinger needs imaging, but imaging should be considered in the setting of persisting symptoms, neurologic deficits, or recurrent events (2 or more stingers). For a single isolated stinger that resolves rapidly with no sequelae, routine imaging of the cervical spine is not necessary. Routine screening of incoming players with no history of stingers or cervical injuries may also be of limited benefit.¹⁵ In other circumstances, plain radiographs to include flexion/extension views should be obtained to rule out bony foraminal stenosis or instability. MRI can be useful to more specifically identify foraminal narrowing or the presence of a disk herniation when a cervical nerve root origin for the symptoms is suspected. CT myelography may be more sensitive in the identification of foraminal or root involvement at times and may give more accurate detail about the extent of central canal stenosis. It should be noted that although canal stenosis has been described in the setting of recurrent stingers, the presence of central spinal canal stenosis raises more concern for a process affecting the spinal cord than a nerve root, while neural foraminal stenosis is more typically associated with a root process such as a stinger.⁴, ¹⁰ In the setting of what is felt to be a significant or recurrent brachial plexus injury, imaging of that region may also be helpful to exclude a mass lesion or identify any focal abnormalities of the plexus.

In the correct setting, imaging can play an important role in establishing the diagnosis or excluding significant underlying pathology associated with persisting or recurrent stingers. Young athletes with a disk protrusion associated with their symptoms may need to be held out of play past the point of symptom resolution to allow for adequate healing and rehabilitation. Those with significant anatomic issues or instability may be best advised to avoid returning to contact sports altogether (fig 1). Neither of these are decisions to be made lightly, nor can they be made without appropriate diagnostic evaluation.

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• Fig 1. 

  Cervical spine CT of a high school football player with recurrent left upper extremity stingers but no persisting neurological deficits. The athlete was advised to discontinue participation in contact sports. (A) Axial view showing narrowing of the left neural foramen at C6/7. (B) Sagittal view showing congenital fusions of C7/T1 and T2/3 (Klippel-Feil anomaly).

What is the Role of EDX? 

While the overwhelming majority of stingers do not require EDX for assessment, this type of testing can be helpful in the management of an athlete with persisting weakness after a stinger. In general, EDX may be more sensitive in the presence of motor deficits than either pain or isolated sensory findings.¹⁶ The sensitivity of these studies may also be lower in athletes with relatively mild injuries and those with a longer time span from the injury. The optimal time frame in which to study an athlete with persisting signs and symptoms after a stinger is about 2 to 4 weeks from the date of injury.⁶ Although the EDX findings of denervation are generally thought of as more qualitative than quantitative, the presence of residual weakness several weeks to a few months out from injury with minimal or no findings of denervation on EDX may suggest a neuropraxic component to the injury, which would be associated with a more favorable prognosis.

EDX can often help in distinguishing between a cervical radiculopathy and a brachial plexopathy. The presence of electromyographic abnormalities in the paraspinal musculature with correlating myotomal abnormalities in more distally innervated musculature and normal sensory nerve conduction studies is generally consistent with a radiculopathy, while plexus injuries are often associated with abnormalities on sensory conduction studies (loss of amplitude of the evoked response) and the absence of abnormalities in the paraspinal muscles. The pattern of electromyographic abnormalities also may not follow a strictly myotomal distribution in a brachial plexus injury. Although EDX can theoretically be helpful in making this distinction, all the information necessary to do so may not be present in a given person. As mentioned previously, Krivickas and Wilbourn² were unable to identify enough of these characteristic features in many of the athletes that they studied to be able to clearly establish the location of the injury to either the plexus or a cervical root.

Serial or delayed EDX may provide information on the presence and extent of neural recovery. In cases where there is a static neurologic deficit with no substantial ongoing recovery, no significant functional deficit arising from the neurological injury, and no significant structural pathology posing an increased risk for further neural injury, RTP may be considered even when EDX abnormalities persist.

What About Longer-Term RTP Considerations for an Athlete With Recurrent Stingers or Persisting Neurological Deficits? 

There are times when it is clearly in the best interest of the athlete to be removed indefinitely from collision or contact sports. A number of factors have to be considered in order to make this decision (see table 1). In general, athletes should meet defined RTP criteria including adequate healing of the injury, restoration of full cervical ROM, aerobic conditioning and strength, and the ability to perform appropriate sport-specific skills without symptoms.¹⁷ Although there are no formal organizational guidelines published in this regard for athletes sustaining a stinger, authors have included persisting weakness, cervical anomalies, persisting EDX abnormalities, evidence of myelopathy, continued pain, and reduced cervical ROM as absolute contraindications for RTP.³, ⁶, ¹⁵, ¹⁸ An athlete sustaining a single stinger requiring a prolonged time for recovery (weeks or months) with a fixed anatomical defect in their cervical spine, such as significant foraminal stenosis due to osteophyte formation, may be best advised to stop participation in collision or contact sports. The presence of a cervical radiculopathy resulting from a cervical disk herniation, with or without a single level cervical diskectomy and fusion, is not an absolute contraindication for RTP provided the athlete recovers physically and functionally to a degree appropriate for the level of contact and activity anticipated.¹⁸ There may be more concern for an athlete who has undergone an upper cervical fusion than one who has had a lower cervical fusion, however.

The number of stingers that an athlete can safely sustain is not known and probably varies highly between athletes. However, 3 or more significant stingers in a season typically prompts consideration for removal of the athlete from play for the remainder of that season, if not permanently.¹, ⁷, ¹⁷ Decisions in this regard can be aided by the appropriate use of imaging and EDX. If athletes with recurrent episodes, even if they resolve rapidly, have significant anatomic issues that would seem to put them at risk for further episodes and potentially permanent neurological injury, they should be removed from participation in collision or contact sports.

Is There a Role for Equipment Modifications in the Prevention of Recurrent Stingers? 

Cervical collars are intended to prevent recurrent cervical injuries by limiting cervical extension and lateral flexion. There is little in the way of clinical data on their effectiveness, however. In a laboratory study of 3 different cervical collars, Gorden et al¹⁹ found that all three of the collars they tested restricted cervical hyperextension more than just a standard helmet and shoulder pads. None of the collars restricted passive lateral cervical flexion, however, and there were no data on the effects of the collars during live-time play. A lack of ability to control lateral flexion would seem to present limitations of the ability of collars to prevent recurrent stingers. Any potential benefit that collars may offer in limiting cervical extension also has to be weighed against the risks of the corollary of this effect, namely the potential for keeping the cervical spine in a relatively flexed position during impact, which may increase the risk for injury to the spinal column. Limiting a player's overall cervical ROM on the field may also limit their effectiveness.

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Conclusions 

Stingers are a common injury affecting young athletes in contact sports. Although symptoms almost always resolve rapidly, some athletes will have ongoing or recurrent problems. Athletes sustaining a stinger should have appropriate evaluation on the field. Those with persisting pain, neurological deficits, or recurrent events warrant a thorough diagnostic evaluation. RTP considerations need to be based on the persistence of symptoms, the extent and subsequent recovery of any associated neurological loss, the pattern of recurrence, and underlying anatomic considerations.

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