Brachial Plexus

Question 1

Innervations of brachium/arm

Answer 1

Anterior compartment: musculocutaneous nerve (flexors of elbow joint)
Posterior compartment: radial nerve (extensors of elbow joint)

Question 2

Innervations of antebrachium/forearm and hand

Answer 2

Anterior compartment: ulnar and medial nerves

Posterior compartment: radial nerve

Question 3

Injury to superior trunk

Answer 3

Erb’s Palsy
Cause: excessive, forceful inc. in angle b/w neck and shoulder
Sensory deficit: lateral aspect of upper limb
Motor deficit: loss of arm abduction, loss of elbow flexion, loss of forearm supination, and weakness of wrist extension.
Presentation: upper limb is adducted, medially rotated and elbow is extended and wrist is flexed (waiter’s tip position)

Question 4

Injury to inferior trunk

Answer 4

Cause: limb is suddenly and/or forcefully pulled in a superior direction
Klumpke’s Palsy
Sensory deficit: Medial aspect of upper limb (except axilla)
Motor deficit: loss of precise finger movement, weakness in forearm pronation, weakness of wrist and finger extension+flexion
Presentation: “claw-hand”, wasting of intrinsic hand muscles When attempting extension, 4th and 5th digits remain flexed.

Question 5

Injury to radial nerve

Answer 5

Causes: can occur with mid-shaft fractures of the humerus. ex. improper use of crutches. Or Saturday night palsy (nerve pinched by sleeping position = inability to extend wrist + digits).
Presentation: Extensors compartments affected, wrist-drop, Paresthesia and/or pain along course of nerve.

Question 6

Injury to axillary nerve

Answer 6

Causes: fracture to surgical neck of humerus or dislocation of glenohumeral joint. Ex. improper use of backpack (quadrangular space syndrome, can involve compression of posterior circumflex humeral artery).
Presentation: Impaired or lost function of deltoid and teres major. Unable to fully abduct arm, or diminished ability to laterally rotate arm. Paresthesia and/or pain along course of nerve.

Question 7

Injury to long thoracic nerve

Answer 7

Causes: nerve damage during surgical removal of lymph nodes or other tissue in axillary region. Or penetrating trauma to the axillary region.
Presentation: serratus anterior affected, winged scapula, inability to raise arms past 90 degrees

Question 8

Injury to ulnar nerve

Answer 8

Causes: Fracture of medial epicondyle of humerus damages nerve, fracture of proximal ulna, medial slashed wrist.
Presentation: damage involves flexors of wrist, digits, and intrinsic hand muscles. Radial deviation at wrist joint, loss of abduction and adduction of fingers, weak wrist flexion and some loss of flexion of digits. Loss depends on where nerve is damaged.

Question 9

Injury to medial nerve

Answer 9

Causes: can be injured by fracture of the humerus above condyles, slashing wrist, or by inflammation or irritation in the carpal tunnel (carpal tunnel syndrome).
Presentation: flexors of wrist and digits affected, also intrinsic hand muscles, particularly those that move the thumb. Pope’s Blessing (when making a fist unable to flex second and third digit). Ape hand (thenar eminence atrophy and loss of thenar opposition. Paresthesia and/or pain along course of nerve.