Thomas Kretschmer and Robert L. Tiel

Case Presentation

This 18-year-old male pedestrian was struck by two cars and thrown under one. He held on to an underslung pipe to avoid having his head crushed and was dragged for ˜100 feet. He sustained fractures to the scapula, ribs, clavicle, and skull and developed a subdural hematoma. When he regained consciousness in the intensive care unit he could not move his right arm and could not lift his fingers, cock his wrists, nor flex his elbow. He noted that he could squeeze his fingers slightly.

Seven months postinjury he noted no recovery of strength above the elbow. He had no pain in the arm. He denied being short of breath since the injury. Physical examination revealed severe atrophy in the supraspinatus, infraspinatus, deltoid, and biceps. There was good rhomboid function and no winging of the scapula. Sensory exam revealed severely decreased pinprick and light touch over the right deltoid area, and anesthesia of radial forearm down to the thumb, index, and middle finger with hypesthesia of the ring and little fingers. Motor grading showed O/5 for deltoid and supraspinatus, infraspinatus, biceps, brachioradialis, triceps, and supinator. Pronator teres graded 3/5. There was no latissimus dorsi function. The upper and lower part of his pectoralis muscle worked and graded 4/5. There was good hand grip, flexor digitorum profundus (FDP; to all fingers), flexor digitorum superficialis (FDS), and his hand intrinsic muscles graded 5. No triceps or biceps tendon reflex could be elicited. There were no findings of a Horner syndrome.

Diagnosis

Right upper trunk stretch injury with involvement of the middle trunk

Anatomy

A proper and systematic clinical exam is key to find out the involved elements, as is knowledge of the plexus anatomy. Examination starts as usual with inspection and gives the first helpful hints. Typical positioning of the limb can give an impression as to whether involvement of either or both upper and lower plexus elements is predominant (upper plexus: Erb palsy; lower plexus: Klumpke palsy). The shoulders, neck, and upper back should be assessed in the beginning, with the examiner viewing the patient from behind. Asymmetries can be detected such as shoulder drop, scapular rotation, or winging. Latissimus dorsi can be assessed from behind by holding the muscle between the thumb and index finger and asking the patient to cough deeply; if intact, the muscle will contract involuntarily. Deltoid, supraspinatus, infraspinatus, biceps, pectoralis, and hand intrinsic atrophy can usually be assessed by simple visual inspection. It is helpful to examine muscles from proximal to distal and to establish a stereotyped routine that is repeated. Based on a thorough clinical exam it is quite often possible to confine the lesion(s) to a certain level(s). After a complete examination one should be able to decide which roots are involved or if a lesion is more likely to be at truncal or cord level, or which combinations are possible. In this case, root avulsion was a definite possibility and required focusing on findings that might suggest a very proximal lesion and thus possibly an avulsed root. The myotomal patterns can quickly suggest which roots are likely to be involved. The myotomal patterns usually suggest: C5—shoulder abduction, C6—elbow flexion, C7—elbow extension, and C8–T1—hand intrinsic muscles. Beware of C7 because C7 may be avulsed but the triceps still functions due to its C6 and C8 contributions.

Characteristic Clinical Presentation

Examination of the areas of preserved sensation can generate a map, which then can be compared with the arm dermatomes C5 to T1. It should be remembered that the T2 dermatome extends onto the medial underside of the arm and is often larger than textbooks demonstrate when the overlapping C8 and T1 dermatomes are not represented due to root avulsion.

The presence of a Horner syndrome or residua of it points toward very proximal T1 damage and is usually an indicator of root avulsion. Sometimes the ptosis resolves, and patients or family members need to be asked if they noticed a drooping eyelid after the accident. In bright light the difference in pupillary size might not be as obvious as expected. The pupils should be assessed in a darkened room, where pupillary differences are more readily appreciated. In general pupillary asymmetry is a more consistent finding than ptosis after injury to the sympathetic ganglion. Phrenic nerve involvement also points to a very proximal level of injury and may be assessed by posterior percussion of the patient’s back in both inspiration and expiration and noting if the level of tympanitic resonance moves inferiorly on inspiration.