Review Question - QID 214473

The patient is presenting with a laceration of the lateral cord of the brachial plexus. Lateral cord plexopathy results in weakness with elbow flexion (biceps), arm pronation (pronator teres), and wrist flexion (flexor carpi radialis). Additionally, there will be sensory loss in the lateral forearm, lateral hand, and the first three fingers which correspond to the antebrachial cutaneous nerve and median nerve.

Brachial plexus injuries are typically the result of a traction mechanism to the upper extremity or penetrating trauma. Deficits correspond to the level of injury, and recovery is dependent on the degree of nerve disruption and age at the time of injury. Injuries can take up to three years to recover, with root avulsions having the worst prognosis. Intact paraspinal muscle function, normal histamine test, elevated hemidiaphragm, and Horner's syndrome are suggestive of a preganglionic lesion (root avulsion).

Moran et al. reviewed the diagnosis and management of brachial plexus injuries. The authors described an advancing Tinel's sign and the presence of a nerve action potential across the lesion on electromyography as positive prognostic indicators. They suggested combining physical exam findings with electrodiagnostic studies to assess the extent of nerve injury and determination if surgical intervention is required.

Sakellariou et al. reviewed the diagnosis and treatment of brachial plexus injuries. They described neurolysis, nerve grafting, neurontization, tendon transfer, free muscle transfer, and arthrodesis as potential surgical treatments depending on the extent of injury and level of recovery. The authors conclude that limb function is nevertheless often disappointing despite recent advances in surgical treatment.

Figure A depicts a diagram of the brachial plexus with the lateral cord identified by the arrow.
Illustration A is a diagram of the brachial plexus with the components labeled.

Incorrect Answers:
Answer 1: Weakness in the pronator teres, flexor carpi radialis, triceps, and extensor digitorum corresponds to middle trunk plexopathy.
Answer 2: Weakness in the deltoid, triceps, and extensor digitorum communis corresponds to posterior cord plexopathy.
Answer 4: Weakness in the flexor pollicus longus, flexor digitorum profundus, and flexor carpi ulnaris corresponds to medial cord plexopathy.
Answer 5: Weakness in the supraspinatus, infraspinatus, biceps, deltoid, triceps, and brachioradialis corresponds to upper trunk plexopathy.