Block 3: TBL 6, Brachial Plexus Flashcards
f(x) of the brachial plexus
to supply motor and sensory innervation to the muscles of the arm, forearm, and hand
Roots of the brachial plexus
anterior rami of C5-T1
What are the divisions of the brachial plexus?
anterior (supply flexors) and posterior (supply extensors) divisions
Describe an upper brachial plexus trunk injury
cause
damaged roots
result
cause: extreme flexion of the head and depression of the shoulder (ex: babies: too much traction pulling the shoulders down during delivery; adults: motorcycle injury)
damaged roots: C5-C6
result: arm hangs limply at the side and is internally rotated; the forearm is pronated and the wrist is flexed, causing the “waiters tip” sign
Describe a lower brachial plexus injury
cause
damaged roots
result
cause: extreme abduction of the arm (ex: babies: pulled by the arm from the birth canal; adults: grabbing on to a tree branch when falling)
damaged rots: C8-T1
result: compromises muscles in the lower forearm and hand (Klumpke’s Palsy)
Klumpkes Palsy: “claw hand”, in which the fingers are flexed
Long thoracic nerve innervates
the serratus anterior muscle
F(x) of the serratus anterior muscle
protracts and upwardly rotates the scapula; keeps the scapula tight against the thoracic cage during arm movement
What happens if there is injury to the long thoracic nerve ?
medial winging of the scapula;
How to test thoracic nerve injury
ask the patient to support their weight with their hands while pushing against a wall
damage to the long thoracic nerve will present as a medial winging of the scapula
When will long thoracic nerve injuries most likely occur?
during a mastectomy
Where does the axillary nerve first course?
through the quadrangular space
What is the function of the axillary nerve?
motor: to innervate the deltoid and teres minor
sensory: skin over the posteriolateral shoulder (sargeant’s patch)
Where is the axillary nerve suspect to injury
fracture of the surgical neck of the humerus or shoulder dislocation
Describe the consequences of axillary nerve injury
- loss of shoulder abduction above 15 degrees b/c of paralysis of the deltoid muscle
- paralysis of the teres minor leads to weakened external rotation of the shoulder & decreased shoulder joint stability
- loss of cutaneous sensation over the posterolateral aspect of the shoulder
What does the radial nerve supply?
the posterior compartment muscles (extensors) and the sensory innervation to the skin on the dorsal side of the arm, forearm and hand
Describe the course of the radial nerve
it travels around the body of the humerus to lie within the radial groove, then travels across the elbow joint anterior to the lateral epicondyle of the humerus
What is at risk with a humeral shaft fracture injury
the radial nerve
What are the branches of the radial nerve?
superficial: cutaneous only; sensory innervation of the dorsum of the thumb and radial 1/2 of the hand
deep (also known as posterior interosseous nerve): motor supply to the posterior forearm by piercing the supinator muscle
What is the main characteristic of radial nerve damage?
wrist drop
Radial nerve injury proximal to the triceps innervation causes
inability to extend the triceps brachii
When is the radial nerve most likely to be injured?
- fracture of the shaft of the humerus
- nerve compression (crutches, a textbook)
- someones head sleeping under your arm “honeymooners palsy”
Musculocutaneous nerve f(x)
motor innervation to the 3 muscles in the flexor compartment of the arm, terminates as the lateral antebrachial cutaneous nerve
Damage to the musculocutaneous nerve causes
loss of sensory component
loss of elbow flexion
severely weakened forearm supination
Ulnar nerve f(x)
innervates:
flexor carpi ulnaris
1/2 FDP
motor to the hypothenar muscles and all other intrinsic hand muscles except for the thenar muscles and 1st 2 lumbricals
