8 min read. Posted in Shoulder

How to Assess the Brachial Plexus “Stinger”

Written by Luke Murray

Introduction

If you work in collision sports such as Rugby or American Football, you’ll likely have heard of a ‘’stinger’’ or ‘’burner’’. You’re on the side-line, you watch the player make a big tackle (or get tackled) and they don’t bounce back up. Like a scene from Baywatch, you sprint over ready to save the day. But the player quickly reassures you: ‘’don’t worry, it’s just a stinger’’. Phew, nothing life threatening, you can breathe a sigh of relief!

Or can you? How do you know it’s ‘’just a stinger’’? How do you even define what a stinger is? These were some of the questions I was asking myself when I started working pitch-side and admittedly, I didn’t know the answers. Therefore, the purpose of this blog is to shed some light on the infamous stinger. We will explore definitions, anatomy, mechanism of injury and clinical presentation, along with the pitch side assessment.

 

Definitions

Stingers are a type of neurapraxia of the brachial plexus and/or cervical nerve roots that are a reversible peripheral nerve injury. It is typically characterised by the presence of burning pain radiating from the neck unilaterally into the hand/arm, lasting seconds to hours. Occasionally, symptoms can involve motor and sensory disturbance that lasts between 24 hours to 6 weeks. Of 569 male rugby players, 21% reported experiencing a stinger during the season, 34% reported a prior history and 76% of all stingers occurring during tackling activities (1). However, due to their transient nature and lack of visible injury, it is likely that they are far more common.

Pitch side medical staff are usually the first to evaluate the stinger. Therefore, understanding the anatomy and mechanism of injury (MOI) is crucial.

 

Anatomy

The brachial plexus is the intertwining group of nerves coursing through the neck, shoulder and axilla which is derived from the distal root components in the neck. It includes spinal nerves C5-T1 and as it passes through the shoulder, it divides into roots, trunks, divisions, cords and branches (nerves). Axons that course through the plexus innervate and supply sensation to all muscles of the upper limbs. Knowing what muscles are innervated by what trunk/cord is essential for the clinician to localise a lesion (2). See figure 1 below for a visual representation of the brachial plexus.

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Figure 1 (Rubin, 2021)

 

Mechanism of Injury (MOI)

A stinger in rugby most often reported during tackling activities in games or training. There are three proposed mechanisms by which stingers can occur (3):

A) A traction injury to the brachial plexus due to an increased neck-shoulder angle. Consider the ball carrier running at speed towards the opponent. The opponent makes a tackle which involves ipsilateral shoulder depression and contralateral lateral neck flexion at the point of impact. There is always a traction risk given this mechanism of injury along with tackles generating forces up to 1500N.

B) Direct nerve compression from a hit to the brachial plexus at Erb’s point (the most superficial location of the brachial plexus where the C5/C6 nerve roots join to form a bundle). In a rugby scrum, consider forces through the neck and shoulder along with the anatomical location of Erb’s point.

C) Cervical nerve root compression caused by ipsilateral lateral flexion or hyperextension of the neck. Again, consider the ball carrier and the opponent making the tackle. However, this time the tackler gets their head on the wrong side of the ball carrier. This could cause extreme cervical flexion or extension which may contribute to a cervical root injury.

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Figure 2 (Bowles et al., 2020)

 

Pathophysiology

For the purposes of this blog, we will outline the MOI using the Seddon and Sunderland classification system (3). Acute stinger/burner symptoms can be categorised into three grades of peripheral nerve injury:

Grade 1: Neurapraxia

Functional damage to the nerve, axonal integrity is preserved, and connective tissue is intact. Damage to the myelin has been proposed as a mechanism which is unable to conduct action potentials leading to transient motor or sensory symptoms. This is the most common and may recover in a matter of minutes, with some research indicating up to 2 weeks to recover.

Grade 2: Axonotmesis

The portion of the axon distal to the site of lesion degenerates (Wallerian degeneration) and its muscle fibers lose innervation and trophic stimuli, determining muscle atrophy related to denervation mechanisms. Prognosis is difficult with these cases where some spontaneously recover and others have poorer outcomes.

Grade 3: Neurotmesis

Permanent damage or complete transection of the nerve. Myelin, axon and connective tissues are affected. Muscles lose their innervation from the nerve and undergo sever atrophy and loss of function. These are catastrophic cervical root avulsions which are uncommon but unfortunately do happen. One such example is former Australian rugby player Rob Horne who was forced into retirement due to cervical root avulsions leaving with him full paralysis of his right arm (4).

 

Clinical Presentation

From the side-line, you may have observed one of the injury mechanisms outlined above. At this stage players can present in a variety of ways. Sometimes they are slightly bent at the waist, with the involved upper limb supported by the uninvolved side. The neck may be side flexed towards the injured side and they may shake their hands or bring their chin to their chest to relieve symptoms. Below is a table of symptoms to be aware of (5).

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Note of Caution

A huge part of diagnosing a stinger is the athlete’s subjective symptoms. This leaves the clinician in a tricky position, as symptoms are often under reported. Ireland and Munster Rugby scrum half Conor Murray suffered a ‘’stinger’’ in the first half against Wales in 2017. He continued to play but suffered with ‘’repetitive stingers’’ for many months afterwards which included weakness and sharp, stinging pain with loss of sensation in the arm (6). With the benefit of hindsight, what would you do in this situation?

 

Immediate Pitch-Side Management

Initial management of stingers in collision sports is the same as managing any trauma patient with a potential cervical spine injury. For side-line medical staff, your priority is to ensure the athlete did not sustain any life-threatening injuries. Therefore, your assessment should involve a standardised method of care ensuring a patent airway and normal breathing, and circulation. It is essential to immobilise and stabilise the cervical spine until assessment for spinal injury can be adequately accomplished (3).

 

Physical Examination

Your physical examination should involve inspection of the neck and shoulder to identify any deformities, fractures or dislocations, palpation of the cervical spine, along with a detailed neurovascular examination. With the contralateral limb as the baseline, a complete motor and sensory exam should be conducted of the upper limbs. Assuming major injuries have been ruled out and pain is not limiting, assess range of motion of cervical spine and upper extremities on the field. Any symptoms associated with neck movement warrants further evaluation. Any weakness lifting the arm may be indicative of a stinger.

Remember, although stingers present with a wide variety of symptoms making it a diagnostic challenge, they must be unilateral. Therefore, bilateral upper limb (or lower limb) symptoms should raise suspicion of a spinal cord injury. When you are confident it is a stinger, you may be able to localise the lesion pitch-side provided the strength and sensory deficits are consistent. However, due to the high anatomical variability within and between individuals, localisation of the lesion can be difficult (5).

 

To Play or Not To Play – That is The Question

So, assuming the patient does not have a life-threatening injury but has a stinger, do you remove from play? If symptoms have resolved by the time you’ve completed your assessment, I think it would be fair to let the athlete return to play. Athletes should not return to play unless they are neurologically intact and have full active pain-free cervical ROM (3).

 

Knowing The Athlete

It is important to know your athlete’s medical history and assess them in the same way you would any other human being. The biggest risk factor for a stinger, is a previous history of stingers! If your athlete has an injury, it is up to you to know if this is their first episode or not. Therefore, you will need to know how many previous stinger episodes they’ve had, the specific symptoms and how long it took to resolve. It is also worth exploring their understanding of stingers as the variety of symptoms may lead to different beliefs and ideas about them.

 

If you want to learn more about athletic shoulder injuries, be sure to check out Dr Rod Whiteley’s brilliant Masterclass on The Sporting Shoulder.

 

Conclusion

That concludes part 1 of the stinger. You now know this is a peripheral nerve injury of the brachial plexus along with the common mechanism of injury, anatomy, signs and symptoms and how to assess pitchside. Stay tuned for part 2 which is on the management of the stinger.

Thank you for reading and please reach out on social media as I’d love to hear about your experience managing stingers.

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