What is the most common mechanism for brachial plexus injuries?
Closed injury (traction, compression, or combination of the two).
What is the most common location of brachial plexus injuries?
Supraclavicular, root, and trunks.
What is the typical mechanism of a C8–T1/lower trunk traction injury?
Forceful abduction of the arm overhead.
What brachial plexus injury is typically produced by violent lateral bending of the head and neck?
Traction injury of C5, C6/upper trunk.
What is a common site for brachial plexus compression injuries?
Between clavicle and first rib, near the coracoid process.
What are the demographics of the majority of patients with brachial plexus injuries?
Male, aged 15 to 25.
What proportion of brachial plexus injuries occur in motor vehicle accidents?
What type of vehicle is most commonly implicated in brachial plexus injuries?
The motorcycle (70% of motor vehicle accidents). Snow mobiles in colder climates.
Lower roots (C7, C8, T1).
How many nerve roots form the brachial plexus?
Five (C5–8, T1).
What term describes a contribution of the C4 nerve root to the brachial plexus?
What phenomenon is described by the term “postfixed” brachial plexus?
T2 contribution to the plexus.
What are the five separate sections of the brachial plexus?
Roots, trunks, divisions, cordserminal branches.
(Robert Taylor Drinks Coffee Black)
What structure is formed by coalescence of the ventral and dorsal rootlets?
The nerve root.
What vascular structure is associated with the C7 root in the exposure of the cervical region of the brachial plexus?
Transverse cervical artery.
The medial cord of the brachial plexus receives contributions from which nerve roots?
C8 and T1.
Where does the nerve root leave the spinal canal?
Through the neuroforamen.
What is contained in the dorsal root ganglion?
The cell bodies of the sensory nerves.
Where do the motor nerves travel?
In the volar root ganglion. (V volar, Vroom!!)
What is described by the term preganglionic brachial plexus lesion?
1. Lesion proximal to the dorsal root ganglion
2. Intradural rupture of the rootlets
3. Avulsion from spinal cord
Upper trunk by C5 and C6.
Middle trunk by C7.
Lower trunk by C8 and T1.
What is Erb’s point?
Point where C5 and C6 merge to form upper trunk.
What structures join to become the posterior cord?
All three posterior divisions.
What is formed by the anterior divisions of the upper and middle trunk?
The lateral cord.
(Imagine a football announcer, “Number 34 runs up [upper trunk] the middle [middle trunk] and throws a lateral [lateral cord]!”)
What continues as the medial cord?
The anterior division of the lower trunk.
The cords are named after their location in relation to which structure?
The axillary artery.
What part of the brachial plexus crosses underneath the clavicle?
What muscles are innervated by the dorsal scapular nerve?
Rhomboid major/minor and levator scapulae.
Proximal to distal:
1. upper subscapular n.
2. thoracodorsal n.
3. lower subscapular n.
4. axillary n.
5. radial n.
What branches originate at the C5 root level?
1. Phrenic n. contribution
2. Long thoracic n. contribution
3. Dorsal scapular n. (levator scapulae, rhomboids)
What are the terminal branches of the medial cord?
Four “medial (or median)” structures and the ulnar nerve.
Medial pectoral n.
Medial brachial cutaneous n.
Medial antebrachial cutaneous n.
Contribution to the median n.
What are the branches of the lateral cord?
1. Lateral pectoral n.
2. Contribution to the median n.
3. Musculocutaneous n.
What branches originate from the upper trunk?
Suprascapular n. nerve to the subclavius.
Where is the inferior cervical sympathetic ganglion located?
In proximity of the T1 nerve root.
What is Horner syndrome?
This constellation indicates a lesion of the cervicothoracic sympathetic ganglion (adjacent to C8, T1) disrupting the oculosympathetic pathway.
How is muscle strength graded?
By the British Medical Research Council grading system:
M0: no evidence of contractility
M1: evidence of contractility but no motion
M2: complete range of motion with gravity eliminated
M3: complete range of motion against gravity
M4: complete range of motion against some resistance
M5: normal power