Stingers and Burners

A stinger/burner is usually an athletic injury from traction, compression, or direct trauma to the upper brachial plexus or cervical nerve roots.¹

There are three generally accepted mechanisms of injury for stingers/burners.

1. Traction injuries occur when there is contralateral lateral neck flexion and/or ipsilateral shoulder depression.
2. Compression injuries occur when the neck is forced into ipsilateral lateral flexion and/or oblique extension.
3. Direct blow injuries occur when there is a blow, often by an opponent’s helmet or shoulder, directly over the supraclavicular fossa or lower lateral neck.

Stingers/burners are commonly reported in collision sports, most notably football, but also including hockey, lacrosse and rugby. Early literature reported the annual incidence of stingers/burners in contact sports at 49-65%, with recurrence estimated at 87%.^1,2 More recent data from 2012 showed an incidence of 26% and lifetime prevalence of 62% in Canadian college football players.³ Approximately 50-65% of football players and 30-40% of rugby players have reported at least one stinger in their career.^4,5 The true prevalence is unknown  as symptoms are often under-reported by athletes for fear of being removed from play; in one study, 70% of American college football players reporting a stinger/burner did not report this to medical personnel. Injuries were more common in those with previous history of injury, and in the following football positions: linebackers, offensive linemen, and wide receivers.⁶

Primary prevention efforts should focus on proper play techniques and protective equipment. A more upright tackling position can prevent the head from being driven into excessive extension during contact. Higher riding padding and the use of a cervical collar can also help absorb the energy from a blow.⁷

Stingers/burners typically affect the C5 +/- C6 nerve roots or the upper trunk of the brachial plexus. Mild injury may result in neurapraxia and conduction block, leading to temporary sensory deficits and weakness that may last from minutes to weeks. More severe injury may result in axonotmesis or neurotmesis, which can lead to long-term sensorimotor deficits.⁸

The role of intrinsic anatomical abnormalities is controversial. The neuroforamina and the central canal are narrowed when the neck is in extension and rotation.^{6, 7} Cervical canal stenosis , measured by a Torg ratio < 0.8, has been correlated with increased risk of stingers/burners in collegiate athletes. A 1994 study found that college athletes with a Torg ratio <0.8 had a threefold increase in sustaining burners.⁶ Similarly, increased risk of burners has been reported high school athletes with central canal or neuroforaminal stenosis.⁷ More recently, a mean subaxial cervical space available for the cord (MSCSAC) < 5mm has also been shown to have a high sensitivity and specificity for chronic stingers/burners, and may have some predictive value.^{9, 10} However, given the high prevalence of similar anatomy in asymptomatic individuals and the high rates of stingers/burners in those without these anatomic features, the exact role of abnormal cervical vertebral anatomy is controversial.¹¹ Even if these anatomic features are correlated with the development of a stinger/burner, they are most likely only predictive for compression type injuries, and not for those due to traction or direct trauma.

Stingers/burners are usually associated with traumatic events, such as collisions, direct impacts, or falls. In collision sports, improper technique or improper equipment may be responsible. If possible, the mechanism of injury should be noted. Patients will complain of immediate onset of severe, unilateral burning pain radiating down the arm, often with paresthesia and motor weakness.

Physical examination should first focus on ruling out other, more severe injuries. Given the high energy impact involved, immediate assessment of airway, breathing, circulation, cervical spine injuries, or other acute shoulder fractures/dislocations is paramount.  If bilateral upper extremity or concurrent lower extremity symptoms are present, the athlete should be treated for potential cervical spinal cord injury, including immediate cervical spine immobilization, spinal precautions and transport by EMS to a trauma center for further evaluation and care. Once emergent medical diagnoses are ruled out, further assessment of the cervical spine, shoulder and neurovascular structures should be completed.

The diagnosis of stingers/burners is typically made by the history and physical examination. The involved extremity is often braced against the body for comfort, held up by the uninvolved limb to relieve tension or set in a depressed position due to weakness. Close inspection should be performed as ecchymosis, swelling, deformity, or asymmetry of the neck, shoulders, clavicles, and scapulae suggests other causes of injury. Focal tenderness to palpation is also atypical and should alert the clinician to suspect other etiologies. Neck and upper extremity range of motion is generally not helpful in the acute stage of injury, due to protective spasms. A baseline neuromuscular exam should be established, including myotomal strength, dermatomal sensory, reflex and neural root tension testing. Transient, unilateral weakness or sensory abnormalities are often identified on neurologic examination.  Serial exams should be performed to assess for resolution of symptoms or identify late-onset symptoms. Testing should focus on C5 and C6 myotomes (deltoid, biceps and infraspinatus) and dermatomes. Biceps, brachioradialis and Hoffman’s reflexes should be checked but are often normal. Spurling’s maneuver may be positive; it has high specificity but low sensitivity.¹³ While weakness is common, atrophy of the neck, shoulder, or arm is suggestive of a more chronic process, such as a chronic stinger/burner or cervical radiculopathy.

Functional assessments should involve cervical and shoulder range of motion, neuromuscular exam, and sport-specific activities.

Imaging should be obtained in the following instances:

• Recurrence of stinger/burner
• Bilateral pain, weakness, or numbness
• Pain, weakness, or numbness lasting more than 24 hours
• Any concern for C-spine injuries

Imaging studies are generally not indicated in the following conditions:

• First incidence of pain
• Unilateral pain
• Symptoms that resolve within 24 hours
• Benign physical examination (without concern for C-spine or shoulder injury)

Imaging should initially consist of: A-P, lateral, and oblique C-spine films. Flexion/extension views can be helpful in demonstrating spinal instability, but should only be done in the hospital setting for acute injuries. If symptoms are bilateral, or there is concern for cervical spine pathology, a C-spine MRI should be obtained to evaluate for spinal cord edema, nerve root integrity, disc herniation, pars interarticularis fractures, ligamentous injury, or foraminal stenosis.

Electrodiagnostic examinations (EDX) can help confirm the diagnosis, define and locate the site and nature of the lesion (axonal, demyelinating), and guide prognosis. EDX can help distinguish between cervical radiculopathy and brachial plexopathy. Decreased conduction velocities, prolonged latencies and proximal conduction blocks on nerve conduction studies are consistent with neurapraxia. If sensory studies are abnormal, this is suggestive of a brachial plexus injury, rather than a radiculopathy, and may suggest a longer recovery process. The presence of positive sharp waves and fibrillation potentials on needle electromyography represents active denervation and axonal injury, which also suggests a longer recovery period; this may take up to three weeks to develop post-injury.¹⁴ Involvement of the cervical paraspinal muscles suggests a nerve root injury rather than plexopathy. While serial EDX can be helpful in case of axonotmesis and neurotmesis to monitor recovery, it is not recommended to base return-to-play decisions on resolution of EDX abnormalities, as functional strength may return prior to the resolution of EDX abnormalities.¹⁵ However, ongoing acute denervation (spontaneous potentials) without evidence of reinnervation (polyphasicity with appropriate recruitment) may suggest that the athlete is not yet ready to return to play.

Given the relatively high incidence of stingers/burners and the rare incidence of permanent disability, the general prognosis appears good. While return to play time can be variable, one report estimated that more than 85% of players did not miss a game or practice after a stinger.³  Lack of prior stingers/burners and rapid resolution of symptoms are considered favorable prognostic factors.¹² In contrast, prior history of a stinger has been shown to strongly correlate with recurrent stingers by more than 50% in some studies.⁶ However, there is no current evidence to suggest that the risk of permanent nerve injury is associated with the number of recurrence.

The patient’s sport, position, and form must be considered when determining return to play, especially for those with recurrent stingers/burners.

Coaches and parents should be educated on injury mechanism and proper sporting technique and equipment. Tackling mechanics should be assessed in defensive football players with recurrent injuries.

If cervical spine injury is considered, spine precautions should be initiated and the patient should be emergently transported to the hospital for more extensive evaluation. The physician must also be aware of the possibility of concurrent or separate shoulder dislocations that can be caused by the same trauma and may present in a similar manner. It would be inappropriate to return athletes to play if they are in need of advanced medical work-up, or have any continued neurologic deficits. Such actions could be a deviation of standard of care and may be considered medical negligence.

There are a number of review articles that outline return to play guideline following burners/stingers.^16-20  While there is variability among these guidelines, all agree that athletes should not return to play until all symptoms have resolved, including full, pain-free cervical ROM, full strength, no tenderness to palpation and normal neurologic examination. Neck pain with decreased ROM, persistent neurologic deficits or evidence of instability are absolute contraindications to return to play. Additional recommendations should consider symptom recurrence and duration:

• First stinger/burner in a season: An athlete may return to play in the same game once they are pain free with a full cervical range of motion, full, symmetric strength in bilateral upper extremities and no neurological symptoms
• Second stinger/burner in a season: An athlete should not return to play in the same game. Formal medical evaluation should be considered. If all symptoms resolve quickly and fully, the athlete may return to subsequent games.
• Third stinger/burner in a season: An athlete should have imaging evaluation before returning to play. Medical personnel should consider having the athlete sit out for the remainder of the season and/or avoiding future contact sports. Three or more stingers, particularly in rapid succession, are often cited as a relative contraindication to return to play. ^{16, 19}
• Any stinger/burner with persistent symptoms requires advanced imaging, medical evaluation and consideration of EMG testing. Return to play should occur only with complete symptom resolution and appropriate medical clearance.

Initial management consists of rest and pain control. Since stingers/burners are generally self-limiting, most patients will quickly return to full participation without any need for pain medications. Ongoing management includes a rehabilitation program that focuses on correcting biomechanical or technical deficits to prevent recurrence. Rehabilitation programs should include cervical ROM and flexibility, shoulder strengthening and stabilization, and correcting muscular imbalances. Proper sporting technique should be reinforced. Protective equipment should be re-evaluated with a focus on improving shoulder padding.

For chronic or recurrent pain, anti-inflammatory or neuropathic pain medications may be helpful but their effects on disease progression are unknown. The role of corticosteroids is controversial.  Physical therapy and a home exercise program may be beneficial and should focus on cervical and shoulder stabilization, ROM, and strengthening affected muscles. If the pain continues to be refractory, a multidisciplinary pain management program may be helpful. Persistent neurological deficits are a contraindication of return to play. If these are noted, athletes should consider termination from further participation in collision sports.

Coordination among the physician, athlete, athletic trainers, coaching staff, and physical therapists can help establish the understanding of the pathophysiology of the condition, and reinforce the importance of proper training, techniques, protective equipment, and direct rehabilitation efforts.

Education should focus on the importance of proper sporting technique to prevent recurrence. In sports with tackling, athletes should be advised against any spearing-type tackling or leading with the head and neck. Athletes and coaches should not hesitate to report any incidence of stingers/burners to the training staff or a physician familiar with stingers/burners.

Treatment outcome is largely based on the resolution of symptoms and return to pre-morbid level of physical activity. Complete recovery is expected in the majority of stingers/burners; however, in chronic cases there may be residual symptoms which usually manifest as myotomal weakness. One case report has shown cervical transforaminal epidural steroid injections to be helpful in alleviating “chronic stinger syndrome” in a patient who failed conservative treatment. ²¹ However, cervical injections are not without risk, and further investigation is needed to support the benefits of this treatment approach.

In sports with tackling, athletes should be advised against any “spearing”-type tackling, as this has been shown to correlate with a higher incidence of stingers/burners.

The exact role of cervical anatomy in the pathophysiology and prognosis is uncertain at this time. The ideal protective padding for primary prevention of this injury in high-risk sports is also unclear. Equipment modifications such as thermoplastic total contact shoulder-chest orthosis, shoulder pad lifts, or a U-shaped neck roll may provide additional support against neck extension, but they have yet to show reduction in risk of nerve injury. ³

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Original Version of the Topic

Yin-Ting Chen, MD, D.J. Kennedy, MD. Stingers and Burners. 09/20/2013.