Nerve Palsies in the Limbs

Question 1

Dermatome

Answer 1

-sensory area of skin supplied by a single spinal nerve

Question 2

Myotome

Answer 2

-group of muscles supplied by one segment of spinal cord

Question 3

Brachial plexus lesions

Answer 3

• downward traction (fall on side of neck)
  - C5, C6 damage
  - deltoid and shoulder muscles, brachialis and biceps
  - Erb-Duchenne paralysis
• upward traction (breach delivery)
  - T1 damage
  - intrinsic muscles
  - Klumpke’s paralysis (hand clawed)

Question 4

Axillary nerve

Answer 4

• roots C5 and C6
• at risk - surgical neck of humerus
• complication of - # humeral neck, shoulder dislocation, Saturday night palsy (pressure on posterior cord of brachial plexus)

Question 5

Axillary nerve damage deficits

Answer 5

• motor deficit - loss of shoulder abduction (deltoid)

- sensory deficit - badge area

Question 6

Radial nerve

Answer 6

• roots C5, C6, C7, C8, T1
• at risk - spiral groove of humerus
• complication of - # humeral shaft, Saturday night palsy (pressure on posterior cord of brachial plexus), exposure of proximal radius

Question 7

Radial nerve damage deficits

Answer 7

• motor deficit - wrist drop (extensors)

- sensory deficit - 1st web space dorsally

Question 8

Median nerve

Answer 8

• roots C7, C8, T1
• in arm, closely associated with brachial artery
• enters forearm by passing between - two heads of pronator teres
• at risk - volar aspect wrist (& cubital fossa)
• complication of - carpal tunnel syndrome, wrist lacerations

Question 9

Median nerve damage deficits

Answer 9

• motor deficit - thenar wasting (monkey hand), pointing finger
• sensory deficit - volar aspect thumb

Question 10

Ulnar nerve

Answer 10

• roots C7, C8, T1
• at risk – behind medial epicondyle of humerus
• complication of - # humeral condyles

Question 11

Ulcer nerve damage deficits

Answer 11

• motor deficit - claw hand, hypothenar & 1st dorsal interosseous wasting
• sensory deficit - little finger

Question 12

Lumbar plexus

Answer 12

-lies on surface of quadratus lumborum and within body of psoas muscle

Question 13

Femoral nerve

Answer 13

• roots L2-4
• largest branch of lumbar plexus
• supplies quadriceps muscles in thigh
• terminates in long fine sensory branch (Saphenous Nerve)

Question 14

Lateral Femoral Cutaneous Nerve

Answer 14

• roots L2, L3
• purely sensory to lateral aspect thigh
• compression causes meralgia paraesthetica

Question 15

Sciatic nerve

Answer 15

• roots L4-S3
• supplies hamstring muscles in thigh (posterior) and part of adductor magnus, and all lower leg and foot muscles via terminal branches (tibial and common fibular nerves) - height of deviation variable
• at risk from posterior dislocation of hip, intra-muscular injections and during surgery

Question 16

Common fibular nerve

Answer 16

• roots L4-S2
• passes around lateral aspect of neck of fibula (at risk)
• divides into superficial and deep fibular nerves

Question 17

Common fibular nerve damage deficit

Answer 17

-deficit causes foot drop and slapping gait