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CHAPTER 10
The nerves of the upper limb
Introduction
An upper limb neurological examination is part of general neurological examination and is used to assess the integrity of motor and sensory nerves which supply the upper limb. Fig. 10.1 shows the cutaneous distribution of the main nerves of the upper limb. Clinical Applications 10.1 and 10.2 at the end of this chapter will explore the practical application of this knowledge.
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The nerves of the upper limb
Table 10.1 Effects of injury to the median nerve
Joint involved Movement affected/deformity produced Explanation for loss/weakness of movement
Effect on shoulder joint None None of the muscles that move the shoulder joint are supplied by median nerve
Effect on elbow joint Flexion, minimal weakness Pronator teres and flexor carpi radialis are paralysed (important flexors—the biceps and brachialis are not supplied by the median nerve)
Effect on radio-ulnar joint Pronation lost Pronator teres and pronator quadratus are paralysed Effect on wrist joint Flexion weakened Flexor carpi radialis, palmaris longus, flexor digitorum
superficialis, flexor pollicis longus, and part of flexor digitorum profundus are paralysed
Ulnar deviation Unopposed action of flexor carpi ulnaris (as flexor carpi radialis is paralysed)
Fig. 10.1 Cutaneous distribution of nerves in the upper limb.
Axillary N.
Medial cutaneous N. of forearm
Medial cutaneous
N. of arm
RADIAL NERVE
Lower lateral cutaneous N.
of arm
Posterior cutaneous N.
of forearm
Posterior cutaneous N.
of arm
Lateral cutaneous N.
of forearm (musculocutaneous;
C.5 & 6) Ulnar N.
Median N.
Superficial branch of radial N.
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Motor distribution
Effect on thumb movements
Flexion of IP joint lost Flexor pollicis longus (only flexor) is paralysed Flexion of CM and MP joints
weakened
Flexor pollicis longus is paralysed. Weak movement brought about by adductor pollicis
Abduction of CM joint weakened Abductor pollicis brevis is paralysed. Weak movement brought about by abductor pollicis longus
Opposition lost Opponens pollicis is paralysed
Effect on MP joints of fingers
Flexion weakened Flexor digitorum superficialis and flexor digitorum profundus in lateral two fingers are paralysed. Weak flexion brought about by interossei (all fingers), medial two lumbricals (medial two fingers), and flexor digiti minimi (little finger)
Effect on PIP joints of lateral two fingers
Flexion lost Flexor digitorum superficialis and profundus are paralysed Extension weakened Lumbricals are paralysed. Weak extension brought about
by extensor digitorum and interossei Effect on PIP joints of
medial two fingers
Flexion weakened Flexor digitorum superficialis is paralysed. Weak flexion is brought about by flexor digitorum profundus
Effect on DIP joints of lateral two fingers
Flexion lost Flexor digitorum profundus is paralysed
Effect on DIP joints of medial two fingers
None Flexor digitorum profundus is uninvolved
Table 10.1 Effects of injury to the median nerve (Continued )
Joint involved Movement affected /deformity produced Explanation for loss/weakness of movement
Median N.
Branch to thenar Mm.
Digital branches. The lateral two lumbricals are supplied by small branches from the two intermediate digital nerves in the palm
Palmar (cutaneous) branch
Median N.
Medial cord of brachial plexus Lateral cord of brachial plexus
Branches to superficial flexor muscles of forearm (except flexor carpi ulnaris) and to elbow joint Anterior interosseus N.
Supplies deep flexors of forearm (except medial half of flexor digitorum profundus) and pronator quadratus
Fig. 10.2 Course and distribution of the median nerve.
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The nerves of the upper limb
Table 10.2 Effects of injury to the ulnar nerve
Joint involved Movement affected/deformity produced Explanation for loss/weakness of movement
Effect on shoulder joint None None of the muscles that move the shoulder joint are supplied by ulnar nerve
Effect on elbow joint None None of the muscles that move the elbow joint are supplied by ulnar nerve
Effect on wrist joint Weakened wrist flexion Flexor carpi ulnaris and part of flexor digitorum profundus are paralysed
Radial deviation Unopposed action of flexor carpi radialis
Effect on radio-ulnar joint None None of the muscles that move the radio-ulnar joint are supplied by ulnar nerve
Effect on thumb movement
None Although adductor pollicis is paralysed, long flexor and extensor of the thumb together mimic the action of the adductor Effect on CM joints of
little finger
Opposition is lost Opponens digiti minimi is paralysed
Effect on MP joints of all fingers (medial four digits)
Abduction and adduction lost All interossei and abductor digiti minimi are paralysed
Effect on MP joints of medial two fingers
Flexion weakened Flexor digitorum profundus, lumbricals, and flexor digiti minimi are paralysed. Weak flexion is brought about by flexor digitorum superficialis
Effect on PIP joints of medial two fingers
Flexion weakened Flexor digitorum profundus is paralysed. Weak flexion is brought about by flexor digitorum superficialis Effect on PIP joints of all
fingers
Extension weakened in all fingers Interossei are paralysed. Lumbricals of medial two fingers are paralysed
No IP extension of ring and little if MP fully extended
Extension possible only when extensor digitorum, extensor indicis, and extensor digiti minimi are not extending MP joint Effect on DIP joints of
medial two fingers
Flexion lost Flexor digitorum profundus is paralysed
Fig. 10.3 Course and distribution of the ulnar nerve.
Palmar (cutaneous) branch Superficial branch of ulnar N.
to muscles of hypothenar eminence
Medial cord of brachial plexus
Ulnar N.
Dorsal branch of ulnar N.
Deep branch of ulnar N. to adductor pollicis, all interossei and medial two lumbricals
Digital branches
Branches to flexor carpi ulnaris and medial half of flexor digitorum profundus
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Motor distribution
Table 10.3 Effects of injury to the musculocutaneous nerve
Joint involved Movement affected Explanation for loss/weakness of movement
Effect on shoulder joint Flexion weakened Coracobrachialis and short head of biceps are paralysed. Weak flexion brought about by deltoid and pectoralis major Stability in abduction lost Long head of biceps is paralysed. Some stability maintained by
deltoid, supraspinatus, and subscapularis
Effect on elbow joint Flexion severely weakened Biceps brachii and brachialis are paralysed. Some weak flexion is brought about by brachioradialis, extensor carpi radialis longus, pronator teres, and flexor carpi radialis
Effect on radio-ulnar joint Supination weakened Biceps brachii paralysed. Supination is brought about by supinator and brachioradialis
Table 10.4 Effects of injury to the axillary nerve
Joint involved Movement affected Explanation for loss/weakness of movement
Effect on shoulder joint Abduction severely weakened Teres minor and deltoid are paralysed. Weak abduction is brought about by supraspinatus
Extension severely weakened Deltoid and teres minor are paralysed Lateral rotation of humerus
weakened
Teres minor is paralysed. Weak lateral rotation is brought about by infraspinatus
Lateral cord of brachial plexus
Lateral cutaneous N.
of forearm
Branch to coracobrachialis Musculocutaneous N.
Branch to brachialis Branch to biceps brachii
Fig. 10.4 Course and distribution of the musculocutaneous nerve.
Posterior cord of brachial plexus
Radial N.
N. to long head of triceps Nn. to medial head of triceps (and anconeus)
Posterior interosseous N.
–Extensor carpi ulnaris –Extensor digitorum –Extensor indicis –Extensor digiti minimi –Extensor pollicis longus –Extensor pollicis brevis –Abductor pollicis longus Superficial branch of radial N.
Digital branches.
Deep branch of radial N.
N. to extensor carpi radialis brevis N. to extensor carpi radialis longus
N. to brachioradialis Radial N.
Posterior cutaneous N. of forearm N. to lateral head of triceps
Lower lateral cutaneous N. of arm Upper lateral cutaneous N. of arm
Axillary N.
Fig. 10.5 Course and distribution of the axillary and radial nerves.
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The nerves of the upper limb
Suprascapular nerve
Table 10.8 shows the effects of injury to the supras- capular nerve.
Radial nerve
Table 10.7 shows the effects of injury to the radial nerve. (See Fig. 10.5 for an overview of the radial nerve.)
Table 10.7 Effects of injury to the radial nerve
Joint involved Movement affected Explanation for loss/weakness of movement Effect on shoulder joint Minor instability of shoulder in
abduction, with tendency for downward dislocation in this position
Long head of triceps brachii is paralysed
Effect on elbow joint Extension lost Triceps is paralysed
Effect on radio-ulnar joint Supination weakened Supinator is paralysed Elbow flexion in mid-prone position
weakened
Brachioradialis, extensor carpi radialis longus and brevis are paralysed. Weak movement is brought about by brachialis, biceps brachii, and pronator teres Effect on wrist joint Markedly weakened radial deviation Extensor carpi radialis longus and brevis are paralysed.
Weak radial deviation brought about by flexor carpi radialis Wrist extension is lost—‘wrist drop’ Extensor carpi ulnaris* and extensor digitorum are
paralysed
Weakened ulnar deviation of wrist Extensor carpi ulnaris* is paralysed. Weak ulnar deviation is brought about by flexor carpi ulnaris
Effect on MP and IP joints Extension lost at MP joint Extension weakened at IP joint
Extensor pollicis longus, extensor pollicis brevis*, and abductor pollicis longus* are paralysed. Weak extension brought about by interossei and lumbricals
Effect on MP joints—index Independent extension lost Extensor indicis* is paralysed Effect on MP joints—little Independent extension lost Extensor digiti minimi is paralysed Effect on CM, MP, and IP
joints of thumb
Extension is lost—thumb Extensor pollicis longus and extensor pollicis brevis* are paralysed. Some extension is brought about by abductor pollicis brevis
Thumb abduction is weakened Abductor pollicis longus* is paralysed. Weak extension brought about by abductor pollicis brevis
* Posterior interosseous branch.
Table 10.5 Effects of injury to the subscapular nerve
Joint involved Movement affected Explanation for loss/weakness of movement
Effect on shoulder joint Instability and tendency for anterior dislocation
Subscapularis is paralysed
Medial rotation of humerus weakened
Teres major is paralysed. Weak medial rotation is brought about by pectoralis major and deltoid
Table 10.6 Effects of injury to the thoracodorsal nerve
Joint involved Movement affected Explanation for loss/weakness of movement
Effect on shoulder joint Medial rotation of humerus is weakened Latissimus dorsi is paralysed Inability to pull the body upwards with the upper limb Latissimus dorsi is paralysed
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Motor distribution