BMS271 - Upper Limb Neuro Flashcards
Brachial Plexus
- 5 nerve roots C5, C6, C7, C8, T1
- nerve roots formed by anterior rami of spinal nerves
- 3 trunks, upper, middle and lower
- upper = C5 and C6, middle = C7, lower = C8 and T1
- Trunks divide into anterior and posterior divisions
- anterior = flexors, posterior = extensors
- 3 cords, lateral, posterior and medial
- cords surround axillary artery
- Cords give rise to 5 major nerves
- Roots and trunks = superior to clavicle
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Dorsal scapular nerve (C5)
rhomboid major, rhomboid minor, levator scapulae
Long thoracic nerve (C5, C6, C7)
serratus anterior
Nerve to subclavius (C5, C6)
subclavius
Suprascapular nerve (C5, C6)
supraspinatus, infraspinatus
Lateral pectoral nerve (C5,C6,C7)
pectoralis major, pectoralis minor
Comes from lateral cord
Subscapular nerves (C5,C6)
subscapularis, teres major
Thoracodorsal nerve (C6, C7, C8)
latissimus dorsi
Medial pectoral nerve (C8, T1)
pectoralis major, pectoralis minor
Comes from medial cord
Medial cutaneous nerve of arm (C8, T1)
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm (C8, T1)
Medial cutaneous nerve of forearm
Myotomes
- Myotome = skeletal muscle tissue innervated by a single pair of spinal nerves
- one myotome may include several muscles (or parts of several muscles)
- one muscle may be part of several myotomes
- Difficult to identify anatomically, but important clinically
hard to differentiate one myotome from the next, but easy to spot functional deficits if one spinal nerve is injured - Muscle groups acting on individual joints may be grouped this way e.g. elbow flexors = C5, C6
Dermatomes
- Dermatome = an area of skin innervated by a pair of spinal nerves
- on the trunk dermatomes are aligned in narrow transverse bands with considerable overlap
- in the limbs the areas of skin are larger
- Two dermatomal maps exist
- one is based on scratch sensitivity tests in patients with herniated IV disks
- the other is based on patients in whom one spinal nerve has been left intact while those above and below are severed
Axillary Nerve
Arises from posterior cord (C5, C6) Passes glenohumeral joint capsule Enters quadrangular space bordered by inferior border of subscapularis teres major long head of triceps brachii surgical neck of the humerus Wraps around surgical neck of humerus Gives off upper lateral brachial cutaneous nerve innervates skin over inferior deltoid and superior triceps Innervates: - glenohumeral joint capsule - deltoid - teres minor - Superior lateral cutaneous nerve of arm: - skin over inferior deltoid and superior triceps
Musculocutaneous Nerve
Arises from lateral cord (C5, C6)
Enters coracobrachialis from axilla
Exits lateral aspect of coracobrachialis and descends between biceps brachii and brachialis
Gives off lateral cutaneous nerve of the forearm
exits from between biceps brachii and brachialis lateral to tendon of biceps brachii
innervates skin over lateral aspect of forearm
Innervates:
- coracobrachialis
- biceps brachii
- brachialis
- humerus
- elbow joint
Lateral cutaneous nerve of the forearm
skin over lateral aspect of forearm
Radial Nerve
Arises from the posterior cord (C5, C6, C7, C8, T1)
Largest branch of the brachial plexus
Descends posterior to brachial artery, then passes posteriorly between the long and medial heads of triceps brachii, runs distally along humerus
Divides anterior to lateral epicondyle into deep and superficial branches
Superficial branch descends on the lateral aspect of the forearm and innervates the skin on the lateral part of the dorsum of the hand
Deep branch pierces supinator, then becomes posterior interosseous nerve and descends between superficial and deep extensors and the interosseous membrane
Terminates on the dorsal aspect of the carpals
Innervates:
- triceps brachii
- anconeus, brachioradialis, extensor carpi radialis longus
Deep branch of radial nerve
Innervates: extensor carpi radialis brevis, supinator, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris
Posterior interosseous nerve
Innervates:
- abductor pollicis longus,
- extensor pollicis brevis,
- extensor pollicis longus,
- extensor indicis
- distal radioulnar joint,
- intercarpal
- and intermetacarpal joints
Superficial branch of radial nerve
- skin on dorsal surface of lateral half of hand (not including dorsal aspect of distal phalanges)
- metacarpophalangeal and interphalangeal joints
Median Nerve detail
Arises from both the medial and lateral cords (C6, C7, C8, T1)
Arises lateral to brachial artery, but crosses it distally to become medial to it
In cubital fossa is superficial to brachialis but deep to bicipital aponeurosis
Passes between heads of pronator teres, travels along forearm between medial and lateral portions of flexor digitorum superficialis
Becomes superficial 5cm proximal to flexor retinaculum, passes through carpal tunnel
Gives off muscular branch and palmar digital nerves
Muscular branch innervates:
thenar muscles
Palmar digital nerves innervate:
skin of digits 1, 2, 3 and half of 4 (palmar surface)
Communicating branch joins median and ulnar nerves in the palm of the hand
Median Nerve innervates
- pronator teres
- flexor carpi radialis
- palmaris longus
- flexor digitorum superficialis
- elbow and proximal radioulnar joints
- lateral half of flexor digitorum profundus
- flexor pollicis longus
- pronator quadratus
- radioulnar, radiocarpal and intercarpal joints
- flexor pollicis brevis
- abductor pollicis brevis
- opponens pollicis
- lumbricals 1 and 2
- skin of palmar surface of digits 1, 2, 3 and lateral half of digit 4
Ulnar nerve details
Arises from the medial cord (C8, T1)
Descends through axilla and upper arm medial to the brachial artery
Descends between olecranon and medial epicondyle
Enters forearm between heads of flexor carpi ulnaris
Descends along forearm on medial part of FDP (medial epicondyle > lateral edge of pisiform)
Crosses anterior surface of flexor retinaculum, hides under palmaris brevis
Divides into deep and superficial branches in hand
Ulnar nerve innervates
- flexor carpi ulnaris
- medial half of flexor digitorum profundus
- elbow joint
- skin on surface of digit 5 and medial half of 4
- flexor digiti minimi brevis
- abductor digiti minimi
- opponens digiti minimi
- lumbricals 3 and 4
- palmar interossei
- dorsal interossei
- adductor pollicis
