Brachial Plexus Flashcards
The brachial plexus provides innervation to:
the upper limb
What is the function of somatic efferents in the brachial plexus?
Motor to voluntary muscles
What is the function of somatic afferents in the brachial plexus?
Exteroceptive- pain, temperature, pressure, touch, vibration (cutaneous)
Proprioceptive- joint and position sense
What is the function of autonomics in the brachial plexus?
Sympathetics to the upper limb that innervate sweat glands and smooth muscle of arteries and hair follicles
How many roots of the brachial plexus are there?
5
What are the roots of the brachial plexus?
Ventral primary rami from:
C5, C6, C7, C8, T1
(sometimes C4 and T2)
The five roots of the brachial plexus form how many trunks?
3
What are the trunks that arise from the five roots of the brachial plexus?
C5 and C6 form the upper trunk
C7 forms the middle trunk
C8 and T1 form the lower trunk
How many nerves of the brachial plexus are derived form the roots and trunks?
4
What are the nerves that arise from the roots and trunks of the brachial plexus?
Dorsal scapular nerve (C4, C5)
Long thoracic nerve (C5, C6, C7)
Nerve to subclavius (C5, C6, sometimes C4)
Suprascapular nerve (C5, C6, sometimes C4)
Each trunk of the brachial plexus divides into how many divisions? What are they?
Divides into 2 divisions: anterior and posterior
How many total divisions are there from the trunks of the brachial plexus? How many nerves arise from divisions?
6 divisions with 0 nerves arising from them
The divisions of the brachial plexus form what?
3 cords
What are the three cords of the brachial plexus?
Lateral cord (C5, C6, C7)
posterior cord (C5, C6, C7, C8, T1)
medial cord (C8, T1)
What nerve is derived from the lateral cord of the brachial plexus?
Lateral pectoral nerve (C5, C6, C7)
What nerves are derived from the medial cord of the brachial plexus?
- Medial pectoral nerve (C8, T1)
- Medial brachial cutaneous nerve (C8, T1)
- Medial antebrachial cutaneous nerve (C8, T1)
What nerves are derived from the posterior cord of the brachial plexus?
- Upper subscapular nerve (C5, C6)
- Thoracodorsal nerve (C6, C7, C8)
- Lower subscapular nerve (C5, C6)
How many terminal branches are formed from the cords of the brachial plexus?
5
Name the terminal branches of the brachial plexus
- Musculocutaneous nerve (C5, C6, C7)
- Median nerve (C6-8, T1)
- Ulnar nerve (C7, C8, T1)
- Axillary nerve (C5, C6)
- Radial nerve (C5-C8, T1)
Where does the musculocutaneous nerve arise from?
Lateral cord of the brachial plexus
Where does the axillary nerve arise from?
Posterior cord of the brachial plexus
Where does the radial nerve arise from?
Posterior cord of the brachial plexus
Where does the median nerve arise from?
Lateral and medial cords of the brachial plexus
Where does the ulnar nerve arise from?
Medial cord of the brachial plexus
brachial plexus injuries
Upper trunk brachial plexus injuries are produced by…
actions that increase the angle between the neck and shoulder
brachial plexus injuries
Upper trunk brachial plexus injuries cause…
a pull, tear, or stretch of C5 and C6 nerve roots or the upper trunk
brachial plexus injuries
How does a patient present with an upper trunk injury?
- Arm is adducted and medially rotated
- Forearm extended
- Palm is facing backward and upward
- Loss of sensation along C5 and C6 dermatome
brachial plexus injuries
Lower trunk injuries occur when…
the upper limb is forcefully pulled in an upward direction that increases the angle between the humerus and thorax
brachial plexus injuries
A lower trunk brachial plexus injury causes…
a pull, tear, or stretch of C8 and T1 nerve roots or the lower trunk
brachial plexus injuries
How does a patient present with a lower trunk injury?
- Clawhand (paralysis of all the small muscles in the hand innervated by median and ulnar nerves)
- Abduction or radial deviation of wrist during wrist flexion (paralysis flexor carpi ulnaris and the ulnar half of flexor digitorum profundus)
- Loss of sensation along the medial side of the arm and forearm and medial two fingers
brachial plexus injuries
What is scalene syndrome?
Hypertonic state of scalenus anterior and medius that compresses and entraps the roots of the brachial plexus
brachial plexus injuries
What is cervical rib syndrome?
Development of a cervical rib from the costal elements of C7 vertebrae that compresses and entraps C8 and T1 nerve roots between it and the first rib
brachial plexus injuries
Compression or irritation of the cords of brachial plexus can occur from…
prolonged hyper ABduction of the arm
brachial plexus injuries
In hyperabduction syndrome, where does compression occur?
Between coracoid process and pectoralis minor; the coracopectoral tunnel
brachial plexus injuries
What is thoracic outlet syndrome?
Compression to lower trunk
brachial plexus injuries
What are the entrapment sites of thoracic outlet syndrome?
- Costoclavicular (between 1st rib and clavicle)
- Coracopectoral tunnel (between pectoralis minor and coracoid process)
- Scalene entrapment (particularly applies to lower trunk)
