Upper limb 1.6

Question 1

What is the brachial plexus formed by?

Answer 1

Anterior rami of C5 to T1 spinal nerves

Question 2

What do the branches of the brachial plexus supply?

Answer 2

Its branches supply muscles of the shoulder, including superficial muscles on the back and anterior thoracic wall and all the muscles of the upper extremity.

Question 3

What is the organisation of the brachial plexus?

Answer 3

• 5 roots
• 3 trunks
• 3 anterior and posterior divisions (lateral, posterior and medial cords)
• 3 cords give rise to 5 terminal branches

Question 4

What do upper plexus injuries affect?

Answer 4

Upper plexus injuries (C5-C6) (Erb’s palsy) affect largely the muscles of the shoulder and arm and present as an extended elbow and flexed wrist (wristdrop) but a normal grasp

Question 5

What do lower plexus injuries affect?

Answer 5

Lower plexus injuries (C7-T1) (Klumpke’s palsy) affect primarily muscles of the forearm and hand; the patient has a weak grasp owing to the loss of flexion

Question 6

What does the radial nerve innervate?

Answer 6

• The radial nerve innervates the extensor compartment of the arm and courses posteriorly to the shaft of the humerus, running with the deep brachial artery
• In the arm, this nerve innervates the triceps and anconeus muscles.
• Innervates the arm’s posterior compartment, which contains muscles that extend the elbow

Question 7

What is Saturday night palsy?

Answer 7

1. The radial nerve is vulnerable to stretching or tearing in fractures of the shaft of the humerus and can be compressed by tourniquets that are too tight or by direct compression (Saturday night palsy) leading to weakened elbow, wrist, and finger extension and supination
2. Wristdrop is a common clinical sign if the forearm extensor muscles are affected.

Question 8

What does the musculataneous nerve innervate?

Answer 8

1. the flexors of the elbow, which are contained in the arm’s anterior compartment.

Question 9

What does the radial nerve innervate in the forearm?

Answer 9

1. innervates the extensors of the wrists and digits, and the median nerve innervates most of the flexors of the wrist and digits (although the ulnar nerve innervates 1 ½ muscles).

Question 10

What does the median and ulnar nerves innervate?

Answer 10

The median and ulnar nerves innervate the intrinsic muscles of the hand, although the ulnar nerve predominates (innervates the hypothenar muscles, 2 lumbricals, the adductor pollicis muscle, and all the interossei)

Question 11

What can median nerve injury affect?

Answer 11

Median nerve injury can affect wrist and finger flexion and, in particular, the ability to effectively use the thumb and index and middle fingers

Question 12

What can ulnar nerve injury effect?

Answer 12

Ulnar nerve injury can present as a clawhand and an inability to effectively use the ring and little fingers, as well as a loss of abduction and adduction of the 2nd to 5th digits

Question 13

How does the median and ulnar nerve innervate the hand?

Answer 13

1. The median and ulnar nerves innervate intrinsic muscles on the anterior (palmar) side of the hand
2. . The median nerve innervates muscles that act on the thumb; these muscles form the thenar eminence and lumbricals of digits 2 and 3.
3. All the other intrinsic muscles of the palmar hand are innervated by the deep branches of the ulnar nerve.

Question 14

How do you test radial sensation?

Answer 14

• Sensation of the skin over the surface of the hand can vary depending on the branching of the radial, median, and ulnar sensory branches
  1. Testing of radial sensation can only be done reliably over the dorsal web space between the thumb and index finger.

Question 15

How do you test median sensation?

Answer 15

-Median sensation is tested reliably on the palmar (volar) aspect of the tip of the index finger

Question 16

How do you test ulnar sensations?

Answer 16

-Ulnar sensation is tested reliably on the palmar aspect of the tip of the little finger

Question 17

Why are lacerations are bad?

Answer 17

-The rich blood supply to the hand via the palmar arches means that lacerations of the palm often bleed profusely and may be difficult to control