Nerves (motor and sensory components) of the upper limb Flashcards
What are the dermatomes of the upper limb?
C4 shoulder
C5 lateral side of arm
C6 lateral side of forearm + thumb
C7 middle + ring finger
C8 medial side of hand, forearm + little finger
T1 medial side of upper forearm + arm
T2 axilla
How should the biceps deep tendon reflex be tested and what are the nerve roots?
Musculocutaneous nerve: C5 + C6.
Rest comfortably with elbow semi-flexed + hand pronated.
Place thumb on biceps tendon + tap briskly with tendon hammer on the nail bed of your thumb.
= brisk contraction of biceps causing flexion of forearm at elbow joint.
Compare with that of the contralateral limb.
How should the triceps tendon reflex be tested and what are the nerve roots?
Radial nerve: C7 + C8.
Ask patient to rest comfortably with elbow semi-flexed + hand pronated.
Support elbow with one hand.
Tap the triceps tendon directly with tendon hammer.
= brisk contraction of triceps causing extension of the forearm.
Compare with that of the contralateral limb.
How would you test the motor and sensory components of the axillary nerve?
Motor: innervates deltoid + teres minor
Ask patient to abduct arm against resistance.
Sensory: innervates skin over shoulder. Test with cotton wool.
Nerve roots: C5 + C6.
How would you test the motor and sensory components of the musculocutaneous nerve?
Motor: innervates biceps brachii, brachialis + coracobrachialis
Responsible for flexion of arm at the elbow + supination of forearm.
Ask patient to flex their arm at the elbow against resistance.
Sensory: lateral surface of forearm. Test with cotton wool.
Nerve roots: C5-C7.
How would you test the motor and sensory components of the radial nerve in the arm and forearm?
Motor: wrist extensors.
Ask patient to extend their wrist, fingers + thumb against resistance.
Sensory: radial aspect of the dorsum of the hand, up to radial half of the ring finger
Test with cotton wool at the dorsal web space between thumb + index finger.
How would you test the motor and sensory components of the ulnar nerve in the forearm and hand?
Motor: flexor carpi ulnaris, flexors of distal phalanx of ring + little fingers, all intrinsic hand muscles except the thenar group.
Ask patient to abduct their fingers against resistance.
Sensory: ulnar portion of dorsum of the hand, 5th digit, ulnar aspect of ring finger, hypothenar eminence.
Test with cotton wool at hypothenar eminenece
How would you perform a basic motor examination of the hand?
Median nerve: thumb opposition with little finger + flexion of thumb IP joint with index finger PIP joint to form an “OK” sign.
Ulnar nerve: abduction of fingers by spreading them apart, + crossing the index + 3rd finger.
Radial nerve: thumb extension to make a “thumbs-up” sign, dorsal wrist extension + extension of fingers at MCP
How would you test the motor and sensory components of the median nerve in the forearm and hand?
Motor: muscles involving fine precision + pinch function of hand:
Thenar muscles, index + middle finger lumbricals.
Ask patient to touch thumb to 5th finger (opposition)- watch thenar muscles contract.
Sensory: Thumb, index, middle + radial side of ring finger. Test with cotton wool at the thenar eminence
Entrapment of which nerve causes Carpal Tunnel syndrome
Median nerve
Where is the ulnar nerve considered vulnerable?
Where it passes posterior to the medial epicondyle of the humerus at the elbow
