S11: end of unit review

Question 1

Describe the basic arrangement of the brachial plexus

Answer 1

Roots = C5-T1
Trunks = superior, middle & inferior 
Divisions = anterior and posterior 
Cords = lateral, posterior & medial 
Branches (5 major) = axillary, radial, median, ulnar & musculocutaneous

Question 2

Describe which roots form the trunks of the brachial plexus

Answer 2

Base of the neck, roots converge to form three trunks
Superior = C5 & C6
Middle = C7
Inferior = C8 & T1
Travel inferolaterally across the posterior triangle of the neck

Question 3

Describe how the trunks become the divisions

Answer 3

Each trunk divides into two divisions within the posterior triangle of the neck
One division = anterior, other = posterior
Divisions leave the posterior triangle & pass into the axilla

Question 4

Describe how the divisions become the cords

Answer 4

Once the divisions have entered the axilla they combine together to form three cords
Lateral cord = anterior division of superior trunk & anterior division of the middle trunk
Posterior cord = posterior division of all three trunks
Medial cord = formed by the continuation of the anterior division of the inferior trunk

Question 5

Name the spinal nerve roots of the terminal branches

Answer 5

Musculocutaneous nerve = C5-7 from lateral cord
Median nerve = C6-T1 from lateral & medial cords
Ulnar nerve = C8-T1 from medial cord
Axillary nerve = C5,6 from posterior cord
Radial nerve = C5-T1 from posterior cord
Long thoracic nerve = C5-7 directly from anterior rami of spinal nerves
Medial pectoral nerve = C8-T1 from medial cord
Lateral pectoral nerve = C5-C7 from lateral cord

Question 6

Describe an upper brachial plexus injury

Answer 6

Causes: excessive increase in angle between neck and shoulder -> trauma or during birth of a baby
C5 & C6 roots are affected -> limb hangs by the side in internal rotation with an adducted arm & extended elbow = waiter’s tip position
Injury to the upper roots = Erb’s palsy

Question 7

Describe a lower brachial plexus injury

Answer 7

Causes: forced hyperextension/hyperabduction -> someone falls from height & grabs onto a tree branch on the way down or if baby’s arm is delivered first
Nerve roots C8 & T1 are affected -> classical presentation is a ‘claw hand’
Injury to the lower roots = Klumpke’s palsy

Question 8

Describe injury to the radial nerve in the spiral groove

Answer 8

Cause: mid-shaft humeral fracture
Extension of elbow will be normal -> nerve supply to long & lateral heads of triceps given off prior to the radial nerve entering the spinal groove
Wrist & fingers flexed = WRIST DROP -> paralysis of brachioradialis & all extensor muscles of the wrist and fingers
Paraesthesia in the distribution of the superficial branch of the radial nerve

Question 9

Describe injury to the median nerve in the arm

Answer 9

Cause: supracondylar fracture of the humerus
Forearm is supinated -> unopposed action of supinator
Flexion of thumb & wrist is weak
Opposition & palmar abduction of the thumb are absent
Clinical appearance when making a fist = HAND OF BENEDICTION
Long standing lesions at rest = APE HAND DEFORMITY
Patient will have sensory loss in the whole of the region supplied by the median nerve

Question 10

Describe injury to the median nerve at the wrist

Answer 10

Causes: penetration injury or compression in the carpal tunnel
Muscles paralysed are LOAF
APE HAND DEFORMITY -> thenar eminence is flattened, thumb is adducted & externally rotated

Question 11

Describe injury to the ulnar nerve at the elbow

Answer 11

Causes: medial epicondylar fracture/compression in cubital tunnel
Loss of sensation in dorsal & palmar cutaneous branches as well as the palmar digital nerves involved in a low ulnar nerve lesion
Less pronounced claw (flexor digitorum is paralysed -> no flexion at the DIPJ of the ring & little fingers)
-only consists of hyperextension at MCPJs & flexion at the PIPJs
Ulnar paradox = you would expect a more proximal injury to produce a more pronounced deformity, but in fact the opposite occurs

Question 12

Describe injury to the ulnar nerve at the wrist

Answer 12

Causes: laceration or compression in Guyon’s canal
Long standing damage = CLAW HAND -> little & ring fingers are hyperextended at MCP joint and flexed at both proximal & distal IP joints (3th & 4th lumbricals are paralysed)
Unopposed extension from extensor digitorum & unopposed flexion from the long flexor muscles
Sensation is lost in the palmar aspect of the ulnar 1.5 digits and the dorsum over the distal phalanges only