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A 26-year-old male sustains a traction injury to his left arm after a motorcycle crash with resulting weakness in this left upper extremity. An electromyography (EMG) done shows normal cervical paraspinal muscle activity. Which of the following statements is true regarding this injury?
The injury has likely resulted in the avulsion of several nerve roots
Physical exam would likely reveal drooping of his left eyelid and anhidrosis
Intact paraspinal musculature on EMG is suggestive of a post-ganglionic lesion
Immediate surgical intervention with neurotization would eliminate weakness and restore function
The patient would show a normal histamine test
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Normal cervical paraspinal muscle activity on EMG is characteristic of a post-ganglionic injury.
Determining whether a brachial plexus injury is pre- or post-ganglionic has important treatment and prognostic implications. Findings that suggest a pre-ganglionic lesion include Horner syndrome (ptosis, miosis, anhidrosis), a medially winged scapula, loss of paraspinal musculature activity on EMG, and a normal histamine test. These injuries tend to have a worse prognosis than post-ganglionic lesions, which show an abnormal histamine test and intact cervical paraspinal activity on EMG.
Moran et al. review brachial plexus injuries. They recommend a baseline EMG for non-operative injuries at 3-4 weeks time after Wallerian degeneration has occurred.
Shin et al. also review brachial plexus injuries. While an MRI can visualize much of the brachial plexus and may be able to demonstrate neuromas, a CT myelogram still remains the primary mode of radiographic evaluation for nerve root avulsion in the acute setting.
Illustration A shows the difference between a pre- and post-ganglionic lesion. Illustration B shows the brachial plexus for reference.
Answer 1: This is the definition of a pre-ganglionic lesion.
Answer 2: Horner syndrome is typically found in patients with pre-ganglionic lesions.
Answer 4: Neurotization is usually only considered for pre-ganglionic lesions.
Answer 5: Post-ganglionic injuries show an abnormal histamine test.
Moran SL, Steinmann SP, Shin AY.
Hand Clin. 2005 Feb;21(1):13-24. PMID: 15668062 (Link to Abstract)
Moran, HANDC 2005
Shin AY, Spinner RJ, Steinmann SP, Bishop AT.
J Am Acad Orthop Surg. 2005 Oct;13(6):382-96. PMID: 16224111 (Link to Abstract)
Shin, JAAOS 2005
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A patient sustains a transection of the posterior cord of the brachial plexus from a knife injury. This injury would affect all of the following muscles EXCEPT?
The posterior cord of the brachial plexus gives rise to the 1) upper subscapular nerve 2) lower subscapular nerve 3) thoracodorsal nerve 4) axillary nerves 5) radial nerve. The upper subscapular nerve innervates the subscapularis. The lower subscapular nerve innervates teres major and also subscapularis. The thoracodorsal nerve innervates latissimus dorsi. The axillary nerves innervates deltoid and teres minor. The radial nerve innervates the triceps, brachioradialis, wrist extensors, and finger extensors. The supraspinatus is innervated by the suprascapular nerve off the upper trunk and therefore would not be affected by an injury to the posterior cord. The anatomy of the brachial plexus is shown in Illustration A.
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A 21-year-old collegiate football player has been diagnosed with a left superior trunk brachial plexus injury following a tackle. Which of the following would most likely be normal on physical exam?
Sensation over the lateral aspect of shoulder
Sensation over radial aspect of forearm
2nd and 5th finger abduction
Examination of finger abduction would be normal in a patient with an isolated superior trunk brachial plexus injury. Finger abduction is performed by the ulnar nerve, which is supplied by the inferior trunk of the brachial plexus.
Superior trunk brachial plexus injuries are thought to occur secondary to traction when an athlete sustains a lateral flexion injury of the neck. Transient injuries are often referred to as "stingers" or a "burner." Symptoms of these injuries are referable to the motor and sensory functions of the axillary, musculocutaneous, and supra-scapular nerves.
Hershman reviewed the etiology of brachial plexus injuries. They showed that superior trunk brachial plexus injuries are usually transient, with 95% of people regaining full neurological recovery with conservative management.
Schenck showed that injuries to the superior trunk will mainly affect muscles supplied by C5 and C6, such as the deltoid, biceps brachii, brachialis, and brachioradialis muscles. Decreased sensation will occur over the lateral shoulder, lateral aspect of the upper limb, as well as the radial half of the volar forearm with these injuries.
Illustration A demonstrates a lateral traction injury that can precipitate this type of superior brachial plexus injury. Illustration B shows a schematic of the brachial plexus. The nerves supplied by the superior trunk of the brachial plexus include the axillary, musculocutaneous, and supra-scapular nerves.
Answer A: Decreased sensation over the lateral aspect of shoulder = axillary nerve.
Answer B: Decreased biceps reflex = C5 +/- C6 reflex arc.
Answer C: Weakness to shoulder abduction = axillary nerve.
Answer D: Decreased sensation over the radial aspect of the forearm = lateral antebrachial cutaneous nerve of the forearm (branch of musculocutaneous nerve).
Clin Sports Med. 1990 Apr;9(2):311-29. PMID: 2183948 (Link to Abstract)
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A good lecture on brachial plexus injury:
HPI - 74 y/o female s/p nonsyncopal fall with left proximal humerus fracture dislocation, sent from outside hospital for definitive treatment
What would you do with the nerve function loss?