Background
Peripheral nerve injuries are not common in noncontact sports. However, in contact and collision sports such as football and rugby, brachial plexus injuries occur often. In a study of Canadian football, brachial plexus injuries were reported to be 26% (21%-32%) of players, during the 2010 football season. [1] In an American football study, the lifetime rate of brachial plexus injuries was 50.3%. [2] The greater incidence of brachial plexus injuries has been suggested to be the result of direct trauma from participation in contact sports. [3, 4, 5, 6, 7, 8]
The result of trauma to the brachial plexus can lead to the cervical "stinger" or "burner" syndrome, which is classically characterized by unilateral weakness and a burning sensation that radiates down an upper extremity. The condition may last less than a minute or as long as 2 weeks, with the latter duration described as a chronic burner syndrome.
Classically, burner syndrome occurs as a result of a blow to the side of the head, shoulder, and/or Erb point. Spinal stenosis can also increase the risk of developing a stinger.
Burners are typically classified as grade 1 or grade 2.
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Grade 1 describes neurapraxia, which is interruption of nerve function associated with demyelination. Remyelination occurs within 3 weeks of the incident, and axonal integrity is preserved. Weakness in muscle strength may be initially present in the acute examination. This may quickly develop and resolve in minutes but can also have a delayed onset.
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Grade 2 involves axonotmesis, which is axonal damage and Wallerian degeneration. Weakness in muscle strength is often present; persistent weakness or bilateral involvement should raise the suspicion of a higher-grade lesion and further diagnostic studies should be performed.
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Epidemiology
United States statistics
Brachial plexus injuries are the most common peripheral nerve injuries seen in athletes. True rate of brachial plexus injuries is difficult to determine due to significant underreporting. Many stingers last briefly, and players do not seek medical attention. Clancy et al reported that 33 of 67 college football players (49%) sustained at least 1 burner during collegiate play. [9] This is supported by Starr's work. [2]
Sallis et al surveyed Division III college football players and reported that 65% experienced brachial plexus injuries. [10] In addition, Sallis reported an 87% recurrence rate in these individuals. Meeuwisse reported that 7.2% of all football injuries were brachial plexus injuries. [11] The positions most frequently involved varies between Canadian and American football but linebackers are common in both. In Canadian football offensive linemen and wide receivers are involved and in American football it is running backs and defensive lineman. [1, 2] This difference may be due to the different rules of the games with the Canadian Football League having 66% passing plays and the National Football League having 56% passing plays.
Kawasaki et al investigated the incidence of stingers in 569 young rugby players and found that the prevalence of a history of stingers was 33.9% and 20.9% experienced a stinger during the season. The study also reported that 37.3% of players experienced a reinjury during a single season. [12]
International statistics
True measure of international occurrence of brachial plexus injuries is undetermined due to significant underreporting in athletes and lack of studies in rugby and hockey involving brachial plexus injuries.
Almost 4% of traumatic injuries related to winter sports activities are brachial plexus injuries. [13]
Functional Anatomy
Injuries to the cervical spine are common. The common level of injury is at C5-C6. Damage to other areas of the spinal area can lead to an array of motor and sensory deficits. The following is a list of cervical nerve roots with the associated area of potential motor and sensory deficits:
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C4 - Trapezius; shoulder; top of shoulders
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C5 - Deltoid, rotator cuff; shoulder abduction; lateral upper arm or distal radius
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C6 - Biceps, rotator cuff; elbow flexion; lateral forearm and thumb
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C7 - Triceps; elbow extension; index and middle finger tips
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C8 - Extension of fingers; distal thumb; fourth and fifth fingers
Sport Specific Biomechanics
The following 3 mechanisms are common to brachial plexus injury:
Traction caused by lateral flexion of the neck away from the involved side (similar to the mechanism in birth trauma)
Direct impact to the Erb point causing compression to the brachial plexus (often associated with poor-fitting shoulder pads)
Nerve compression caused by neck hyperextension and ipsilateral rotation (The neural foramen narrows in this mechanism.)
Prognosis
Prognosis is good, yet some possibility of chronic symptoms may remain.
Complications
Chronic burner syndrome is a complication of brachial plexus injury
