What is it?
Stingers are seen most by football players, more specifically defensive football players, but any athlete can attain a stinger. A stinger, sometimes referred to as the following: burners, hotshots, zingers, and nerve concussions are intensely painful sensory paresthesia that can last from a few seconds up to a few minutes and are accompanied by some sort of upper extremity weakness.
The weakness is of varying severity and can last from 15 minutes to longer depending on the severity. All stingers may start out with the exact same symptoms, but the underlying injury can be quite different in severity and may affect either the brachial plexus or the nerve root.
These symptoms usually indicate an injury no more proximal than the nerve root and are often experienced unilaterally. Simultaneous symptoms in both upper extremities often signals a spinal cord injury, and should be treated extremely cautiously as a medical emergency.
There is a wide spectrum of injury that can result from a stinger, such as the following: a single transient nerve irritation with no residual deficits; those recur as many as 50 times during a season with no residual deficits; complete avulsion of the nerve roots at the level of the spinal cord that results in permanent anatomic and functional deficits to the upper extremity.
The major point is that all stingers are not the same and it is important that clinicians, trainers, coaches, and athletes understand this. They are symptoms of neurologic insult to either the brachial plexus or the nerve root, which must be evaluated systematically so that the appropriate treatment regiment can be delivered. Since recurrent stingers can result in more severe residual injuries, it is imperative that the treatment includes trying to prevent recurrent injuries.
Mechanism and Frequency
As stated before stingers are most seen in tackle football, but they do occur in other sports as well. Some of the other sports include the following: wrestling, backpacking, sledding, skiing, horseback riding, boxing, weight lifting, and mountain climbing. Since most of stingers occur during football, we will delve into these injuries.
The mechanism of stingers usually involved the athlete’s shoulder colliding with another athlete, the ground, or another object and depressing the shoulder at the same time the cervical spine is hyperextended, hyperflexed, or laterally flexed to the opposite side. As a result the angle of the shoulder-neck is pushed beyond its normal range, which stretches the brachial plexus on the side of the contact. From the stretching of the brachial plexus the C5-C6 nerve roots are injured. Almost 50% of some collegiate varsity football teams’ players can suffer this injury in a four year period of time. Up to 10% of these may be serious enough to cause neurologic deficits that last several hours or longer.
Stingers occur a lot more in college and professional athletes than high school , and it is clear that defensive backs, linebackers, and defensive ends are more likely to receive stingers than other players.
Pathophysiologic Basis of Stingers
Severe burning, stinging paresthesia, and anesthesia in one upper extremity radiate from the shoulder distally through the arm as far as the fingers. The burning and accompanying weakness, most often of the shoulder abductors, external rotators, and elbow flexors are from a neural injury and can last from a few seconds to years.
The severity and duration of the symptoms is determined by the extent of damage to the neural elements. The classification that we’ll use is an electrophysiologic method that correlates to Sunderland’s classification system:
Transient neurapraxia is a transient block of the neural conduction owing to temporary loss of myelin (Schwann Cell) function around the axon. Since it usually takes only a few minutes for this process to be resolved, it is most likely only a mechanical and vascular response of the neural elements with no structural damage. Once myeline function is restored, the player is symptom free, but may still have some soreness and bruising around the shoulder and at the supraclavicular triangle.
Neurapraxia is a injury to the myelin sufficient to cause the body to actually absorb the injured cells and synthesize new Schwann Cells, which then go through a maturation process to replace the damaged ones. This reparative phase takes varying amounts of time depending on the number of cells needing to be replaced and their location. Most of the neural function is back to normal within 2 to 6 weeks.
Axonotmesis occurs when the injury is sufficient to cause damage to the axon and the myelin, which results in actual degeneration of the motor unit organization , which causes the clinically detected weakness. The findings in the electrophysiology during this phase should correlate with the findings clinically (weakness). This type of nerve injury usually regenerates to proximal muscles in 5-6 months.
Neurotmesis is damage of the axon, surrounding myelin, and adjacent connective tissue, sometimes including the epineurium that is so extensive that regeneration is very poor and loss of function is permanent. The problem is that during the regeneration phase, the structures of the involved axons are too severely damaged to allow regeneration . The only increase in strength comes from collateral sprouting of spared axons into the denervated muscle fibers to create larger than normal muscle fibers per motor axon.
Evaluation and Treatment
Stingers are very easy to notice for doctors, trainers, or coaches because an athlete during competition will usually run off the field holding a limp arm to his/her side. Whoever is responsible for the athlete’s care should immediately ask the athlete where it hurts and how the injury was sustained. In order for appropriate inspection the athlete should remove as much protective gear as possible, so that the cervical spine, shoulders, and arms can be examined.
All of the following should be examined: range of motion of the cervical spine and the upper extremities, manual muscle testing of the upper extremities, gross sensation to light, and reflexes. The athlete should be checked repeatedly throughout the remainder of the game. After the game the athlete should be further examined in the locker room, with the previous tests performed and also more tests to get a good feel for the extent of the injury. Participation is withheld until the player is examined by the appropriate professional to ensure that no weakness has developed.
Despite the rules being changed in 1979 to prevent the use of the head for spearing or butting in football due to the large number of cervical injuries, still stingers occur. A high-quality shoulder pad is helpful in absorbing the compression forces received in aggressive shoulder tackling. Once a football player or any athlete receives a stinger additional padding to the shoulder and neck can be helpful.
Due to the fact that muscles and bones protect the brachial plexus and nerve roots from injury, soreness from strain and contusion of the scalene, trapezius, and levator scapulae muscles is often associated with a stinger. To minimize bruising, ice should be used immediately, followed by heat after the first 72 hours. Strengthening exercises should be used during the season and off season because it has been documented that stingers often recur and recurrence can cause neurologic deficits. Strengthening will decrease the likelihood of recurrence thus it is worthwhile.