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Burners (stingers): Acute brachial plexus injury in the athlete

Burners (stingers): Acute brachial plexus injury in the athlete
Literature review current through: Jan 2024.
This topic last updated: Oct 26, 2022.

INTRODUCTION AND TERMINOLOGY — Upper extremity nerve injury commonly results from impact to the neck and shoulder. One such injury, a burner (also called a stinger), generally results from traction or compression of the upper trunk of the brachial plexus or of cervical nerve roots 5 or 6. Burners are typically transient, but they can cause prolonged weakness resulting in time lost from athletic participation. They commonly recur, leading to further disability. Returning to sports activity requires restoration of pain-free motion, complete recovery of strength, full functional status, and addressing predisposing factors.

Other injuries among athletes that involve the neck or upper extremity are discussed separately. (See "Overview of musculoskeletal neck injuries in the child or adolescent athlete" and "Traumatic causes of acute shoulder pain and injury in children and adolescents" and "Throwing injuries of the upper extremity: Clinical presentation and diagnostic approach".)

PATHOPHYSIOLOGY — A burner is caused by trauma to the neck and shoulder and signifies peripheral nerve dysfunction or injury. In most cases, it is a brachial plexopathy involving the upper trunk (figure 1). However, several authors also describe cervical nerve root lesions [1-5]. (See "Brachial plexus syndromes", section on 'Traumatic plexopathies'.)

Three mechanisms of burners are known:

The first is traction injury to the brachial plexus, which occurs when the shoulder is depressed and the neck is forced laterally away from the involved side, stretching the brachial plexus [1,6,7].

The second is a direct blow to the supraclavicular fossa, which causes a percussive injury to the upper trunk of the brachial plexus [4,5,7].

The third is nerve compression by a combination of neck hyperextension and ipsilateral lateral flexion [7]. One author observed the most persistent and severe symptoms from burners developed with neck hyperextension and ipsilateral rotation [8].

The role of abnormalities of the cervical neural foramina, canal, and discs is controversial. Cervical neural foramina narrow significantly with 20 to 30 degrees of neck extension. Cervical rotation further compromises this space [7]. Several studies have documented cervical stenosis (narrowing of the spinal canal) and disc abnormalities in collegiate or professional athletes with compressive burners [9-11]. One study found a statistically significant association of foraminal stenosis and/or canal stenosis among high school athletes with burners compared with controls [12]. However, asymptomatic individuals can have similar findings [13]. Thus, the significance of such radiographic findings is not always clear. Furthermore, the definition of cervical stenosis used in some of these studies has been questioned [14,15].

Nonetheless, compared with the other two mechanisms of burner, the compression mechanism appears more common in higher levels of competition, such as collegiate and professional football, and more closely associated with a chronic course. In a retrospective study of 103 elite collegiate football players (including 28 with and 75 without chronic burners) and 42 matched non-athlete controls, T2-weighted midsagittal magnetic resonance imaging (MRI) of the cervical spine was used to measure the space available for the spinal cord (SAC) at four cervical levels (C3 to C6), and the mean subaxial cervical space available for the cord (MSCSAC) was calculated [16]. For the three groups (athletes with chronic burners, athletes without chronic burners, and controls), the mean MSCSAC results were 4.5 mm, 5.8 mm, and 6.7 mm, respectively; an MSCSAC <5 mm indicated a sixfold risk of neurologic symptoms compared with an MSCSAC of >5 mm. However, this finding requires prospective confirmation.

Classification — Peripheral nerve injury is often graded using Seddon's classification [17]:

Grade I is neurapraxia, a disruption of nerve function involving demyelination [18,19]. Axonal integrity is preserved, and remyelination follows within three weeks [18]. Electromyography (EMG) is typically normal.

Grade II is axonotmesis, in which axonal damage [18] and Wallerian degeneration occur [19]. In contrast with grade I injuries, grade II injuries are associated with electroconduction changes on EMG within two to three weeks.

Grade III is complete nerve transection (neurotmesis) or permanent nerve injury.

Burners typically represent a grade I or II injury. Grade III peripheral nerve injuries are rare in sports and are not characteristic of burners [18]. These most severe injuries usually require higher speeds or forces than occur in most contact sports. They are reported in water skiing, Nordic skiing, body surfing, and rugby [20].

EPIDEMIOLOGY — Burners are a common contact sport injury resulting from trauma to the neck and shoulder. The injury occurs most often in football and rugby, but has also been reported in wrestling, gymnastics, hockey, basketball, boxing, and weight lifting [21,22].

Although burners are common, the true incidence in each sport and at different levels of competition is uncertain, primarily because of underreporting by athletes.

One survey of American college football players found that 65 percent of players had experienced at least one burner in their college careers; 70 percent did not report the injury to medical personnel [6]. Another survey of American college football showed 2 stingers per 10,000 athlete exposures; 19 percent were recurrent [23].

In a survey of Canadian college football players, the one-year incidence of burners was 26 percent and the lifetime prevalence was 62 percent [24]. Offensive linemen incurred the most burners, followed by linebackers, wide receivers, defensive backs, and defensive ends.

A retrospective survey of English Premiership rugby union football players reported that the incidence of stingers (ie, burners) over the course of one season was 72 percent [21]. Most occurred when tackling.

CLINICAL FEATURES

Pain — A burner is caused by trauma to the neck and shoulder and is characterized by pain radiating down one upper extremity. Immediately after contact, the player classically feels burning pain in the supraclavicular area. It radiates down the arm, generally in a circumferential, nondermatomal pattern. The player might also note numbness, paresthesias, or weakness in the extremity. Frequently the discomfort resolves spontaneously in one to two minutes [1].

Important questions for the athlete suspected to have a burner include detailed descriptions of immediate and residual symptoms. Pain quality, intensity, location, radiation, and duration provide clues, as does the presence of numbness, paresthesias, and weakness. Both the athlete and observers can describe the exact mechanism of injury. Because burners frequently recur, information on previous burners and their treatment is relevant to the chronicity of the disorder. Previous burners in either arm raise the possibility of cervical spinal stenosis.

While burners are usually brief and self-limited, recovery can take weeks or months in some cases. The injury often recurs and occasionally leads to a chronic syndrome. (See 'Prognosis' below.)

Examination findings — Physical examination begins with inspection. Acutely the player might shake the upper extremity or hold it against the body to reduce discomfort [1].

Atrophy – Atrophy or asymmetry in the neck, shoulder, or upper extremity suggests previous injury or a predisposition to injury. Shoulder depression and atrophy of the deltoid and supraspinatus commonly develop after burners because of weakness from nerve injury and subsequent maladaptive use of the shoulder [5]. Such changes usually take a few weeks to develop.

Tenderness – Palpation localizes tenderness and spasm, which are not specific for burners. Focal cervical vertebral tenderness should alert the clinician to the possibility of a serious cervical injury, such as fracture or disc herniation, and is not typical of burners. Provided cervical stability has been established, range of motion in the neck and shoulder is evaluated because restricted mobility increases the risk of reinjury. Sensation, strength in each upper extremity myotome, and muscle stretch reflexes should also be examined.

Spurling test and percussion of the supraclavicular fossa for tenderness or Tinel sign may be positive. The Spurling or neck compression maneuver attempts to reproduce radicular pain (picture 1). It is performed by applying downward pressure or tapping on top of the head in several positions. This maneuver is highly specific for the presence of cervical root compression, but the sensitivity is low [25]. Thus, a positive test is helpful, but a negative test does not rule out radiculopathy.

Weakness – Deficits in burners usually involve muscles innervated by C5 or C6, the nerve fibers of which travel through the upper trunk of the brachial plexus (figure 1) [7,18,19,26]. Each of these areas should be tested manually.

The deltoid is innervated by the axillary nerve (C5, C6) and is responsible for shoulder abduction.

The supraspinatus is innervated by the suprascapular nerve (C5, C6) and is responsible for "empty can" abduction. This is performed with the shoulder abducted 90º, the arm in the plane of the scapula, and the thumb directed downward, as if the patient poured a can of liquid. The examiner then resists abduction from this position.

The infraspinatus is innervated by the suprascapular nerve and is responsible for external rotation.

The biceps brachii is innervated by the musculocutaneous nerve (C5, C6) and is responsible for elbow flexion and forearm supination.

The pronator teres is innervated by the median nerve (C6, C7) and is responsible for forearm pronation.

The triceps brachii is innervated by the radial nerve (C7, C8) and is responsible for elbow extension.

The abductor digiti minimi is innervated by the ulnar nerve (C8, T1) and is responsible for abduction of the fifth finger.

Although weakness can resolve within a few minutes of the acute injury, it can also develop hours or days later [1,6,19]. Reexamination of patients with burners until normalization is imperative. The baseline strength of some athletes is so high that manual muscle testing might not detect subtle deficits; comparing one side with the other can be helpful [27].

DIAGNOSIS AND EVALUATION

Clinical diagnosis — The diagnosis of burners can usually be made by the history and physical examination. Diagnostic studies are not necessary in most patients but may be valuable in select cases to exclude injury to the spine or central nervous system. Brain injury is likely if there is altered mental status, while concern for spinal cord injury should be raised if there is associated neck pain, decreased cervical range of motion, or neurologic symptoms affecting more than one extremity [28]. However, since most burners and stingers are transient, lasting minutes to hours, no additional diagnostic studies or treatment are usually required.

Diagnostic testing for patients with atypical features — Diagnostic testing may be warranted for patients with atypical features to evaluate for more proximal (cervical spine) or distal (peripheral nerve) processes.

Cervical imaging — Imaging is indicated in selected individuals to evaluate for cervical spinal stenosis or the rare case of bone injury. Cervical spine radiographs should be performed in patients with severe neck pain, focal cervical spine tenderness, limited cervical range of motion, weakness, or recurrence [18,19,29]. Studies should include anterior-posterior, lateral, and oblique views. Flexion and extension lateral views should be done to search for evidence of cervical ligament injury causing instability [18].

In cases when involvement of the spinal cord or nerve roots cannot be ruled out, magnetic resonance imaging (MRI) or computed tomography (CT) can delineate abnormalities. The author's indications for advanced imaging include neurologic symptoms or signs that are not improving on a daily basis, bilateral symptoms, or recurrence within one year. MRI is more sensitive than CT for visualizing discs and nerves, whereas CT is better than MRI for measuring spinal stenosis. Findings with these studies should be correlated with the athlete's precise clinical presentation, since abnormalities such as foraminal narrowing and disc bulging can be asymptomatic [13].

Electrodiagnostic studies — Electrodiagnostic studies can confirm the diagnosis, localize the lesion, and assess its severity. Findings in burners include fibrillation potentials, delayed conduction, prolonged latencies, and positive waves [2-4]. These tests should be reserved for patients with symptoms lasting at least three weeks, because of the delay between the injury and the onset of electromyography (EMG) changes and the cost of testing [1,18,19]. In one study, for example, weakness was evident on physical examination at least four hours after burners, but the EMG was normal four weeks later [30]. EMG also does not always distinguish lesions of cervical roots from those in the upper trunk [1].

Differential diagnosis — In the acute setting, ruling out serious injuries such as cervical fracture, cervical dislocation, or spinal cord contusion prior to further evaluation is critical. Bilateral symptoms, cervical vertebral tenderness, or lower extremity findings indicate cervical fracture or spinal cord injury until proven otherwise. (See "Cervical spinal column injuries in adults: Evaluation and initial management".)

The differential diagnosis also includes cervical disc herniation with nerve root impingement, shoulder or arm muscle strain, thoracic outlet syndrome, clavicle fracture, shoulder subluxation or dislocation, and acromioclavicular sprain [6]. (See "Clinical features and diagnosis of cervical radiculopathy" and "Evaluation of the adult with shoulder complaints" and "Clavicle fractures" and "Shoulder dislocation and reduction" and "Acromioclavicular joint injuries ("separated" shoulder)" and "Brachial plexus syndromes".)

Repetitive athletic arm movements (eg, pitching, swimming) have been associated with cases of neurogenic, arterial, and venous thoracic outlet syndrome, whereas neck hyperextension/flexion injury has been implicated with the disputed form of thoracic outlet syndrome. (See "Brachial plexus syndromes", section on 'Thoracic outlet syndrome' and "Overview of thoracic outlet syndromes".)

MANAGEMENT — The management of burners includes:

Addressing predisposing factors

Correcting strength deficits

Enhancing protective equipment

Improve strength and flexibility — Flexibility and strength of the neck, shoulder, and upper extremity are important because stiffness and weakness both predispose to and are consequences of burners [1,18,31]. Chest-out posturing is advocated; this position opens the neural foramina maximally, reduces the compressive effect of the weight of the head upon nerve roots, and decreases pressure on the brachial plexus by the scalene muscles [11,31].

Improving flexibility, strength, and posture is a general approach to injuries and is recommended for burners [32,33]. The first goal is to restore pain-free mobility. Strengthening is then addressed with concentric (muscle shortening) and eccentric (muscle lengthening) loading of muscles in the neck, in those that achieve chest-out posture and in those weakened by the injury. Sport-specific therapy follows, which should be continued at least through the season [27]. Physical therapists and athletic trainers can be invaluable in co-managing recovery with the clinician. Finally, functional progression is achieved through evaluation of the athlete's playing style. Correcting suboptimal sports technique should minimize the risk of reinjury [6,27].

Optimize protective equipment — Protective equipment is also advised. Shoulder pads that ride high, have air flotation pads, or are raised by supplemental pads called lifters can reduce the incidence of burners [4,5]. These modifications improve fit, reduce direct pressure on the neck, and augment shock absorption [7,31]. A study of five asymptomatic football players demonstrated statistically significant limitation of cervical extension with a neck roll, a Cowboy Collar, or a custom orthosis compared with shoulder pads alone; the custom orthosis had the largest effect [34]. A biomechanical study showed a Kerr Collar and a Bullock Collar reduced head accelerations and forces transmitted to the neck [35]. Another study found a padded Orthoplast orthosis improved burner symptoms in three of five players over one season [5].

A trial of any of these devices is reasonable. Neck rolls are the least expensive. They should fit snugly below the helmet and remain in place in order to limit excessive motion consistently. Neck rolls and Cowboy Collars are readily available in sporting goods stores. Kerr Collars can be purchased online from the manufacturer. Custom orthoses cost more but have the advantage of individualized fit. Although limiting excessive cervical motion is the goal, straps binding the helmet to the shoulder pads are unsafe and inappropriate [1,18].

There is no role for nerve blockade or glucocorticoid injection in the treatment of burners, and no clinical evidence to support injection therapy for acute brachial plexus injuries.

Follow-up and returning to sport — Athletes with burners should be evaluated at the time of injury and after the practice or game. They should then be examined during the next week, one week later, and afterward as needed until symptoms resolve, motion of the neck and shoulder become full and pain free, and strength normalizes [1,7,15,18,30,32,36,37]. Careful attention to subtle differences between the involved and uninvolved sides is essential.

The standard of care is to await complete resolution of symptoms and full painless range of neck motion after each injury before allowing return to contact sports [38]. The athlete should not be allowed to return if a neurologic deficit persists. Abnormalities on electromyography (EMG) can persist for months or even years after motor deficits have resolved. Thus, obtaining an EMG for the purpose of making decisions about returning to play is not recommended [1,18,30,32].

The athlete must remain asymptomatic during practices to continue competing. Some athletes might feel apprehensive about participation after a neurologic injury has resolved; they may benefit from psychological support [27].

PROGNOSIS — Burners frequently recur. One study of college football players found 87 percent had a recurrence [6]. Another study found that of 36 athletes with neck injuries causing time loss from participation, most of whose symptoms were consistent with burners, 15 (42 percent) experienced subsequent neck injuries [39].

The risk of permanent nerve injury from recurrent burners has not been elucidated, and it is unknown if the risk is associated with the number of recurrences. Considering the high incidence of burners and the infrequency of reports of permanent injury, the risk appears low. However, burners certainly can lead to chronic signs and symptoms that limit athletic participation [9]. Athletes with persistent symptoms should not return to sports that risk burners.

PREVENTION — The preparticipation examination provides an opportunity to screen for patients at risk. The clinician should inquire about previous burners [6]. Limitations in flexibility and strength should be sought manually. Abnormalities detected by history and physical examination should be addressed with a therapeutic plan to improve range of motion, strength, and technique. Individuals with a previous burner or those identified to be at increased risk should consider using the protective equipment described above [31].

Screening radiography is not done routinely. A study of college football players found that those with abnormalities on neck examination or radiograph had nearly twice the risk of neck injury (13.5 versus 7 percent) [39]. Until cost-benefit analysis is performed, however, screening radiographs should be individualized but are not recommended for the general contact sport population.

SUMMARY AND RECOMMENDATIONS

Definition and pathophysiology – A burner is caused by trauma to the neck and shoulder and signifies peripheral nerve dysfunction or injury. In most cases, it is a brachial plexopathy involving the upper trunk. Neurapraxia or axonotmesis can occur with traction or compression involving either the upper trunk of the brachial plexus or the C5-C6 nerve roots. (See 'Pathophysiology' above.)

Clinical features – Immediately after contact the player classically feels burning pain in the supraclavicular area. It radiates down the arm, generally in a circumferential, nondermatomal pattern. The player might also note numbness, paresthesias, or weakness in the extremity. (See 'Clinical features' above.)

Exam findings – While burners are usually brief and self-limited, recovery can take weeks or months in some cases. Weakness often resolves within a few minutes of the acute injury but may develop hours or days later. Reexamination of patients with burners until normalization is imperative. (See 'Examination findings' above.)

Diagnosis and testing – The diagnosis of burners can usually be made by the history and physical examination. Diagnostic studies are rarely necessary. Imaging is indicated in selected individuals to rule out the rare case of bone injury or congenital abnormality. Electrodiagnostic studies are generally reserved for patients with persisting symptoms to confirm the diagnosis, localize the lesion, and assess its severity. (See 'Diagnosis and evaluation' above.)

Management – The management of burners includes addressing predisposing factors, correcting strength deficits, and enhancing protective equipment. Pain-free range of motion, full strength, and protective equipment are the cornerstones of therapy. The athlete must remain asymptomatic during practices to continue competing. (See 'Management' above.)

Prognosis – Burners frequently recur. The precise risk of permanent nerve injury from recurrent burners is unclear but appears to be low. (See 'Prognosis' above.)

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