Brachial Plexus & Neurological Patterns of the Upper Limb Flashcards
Brachial Plexus
-Major nerve network of the upper limb which forms in the neck
-Passes through & is vulnerable to compression:
b/w anterior & middle scalene muscles
-through cervicoaxillary canal (a space bound by the clavicle, rib 1 & scapula)
-Within the axilla
-Formed by the union of lower four cervical ventral rami (C5,6,7,8) plus first thoracic ventral rami (T1), therefore (C5-T1)
Brachial Plexus – structure
Artificially divided Roots
-Ventral rami of C5-T1 spinal nerves
Trunks (named according to location)
- Superior trunk (C5 & C6)
- Middle trunk (C7)
- Inferior trunk (C8 & T1)
Divisions (each trunk divides into an anterior and posterior division)
- Anterior divisions
- Posterior divisions
Cords (named according to their relation to the axillary artery)
- Lateral cord
- Medial cord
- Posterior cord
Branches
- Musculocutaneous nerve – lateral cord
- Median nerve – formed by the union of the medial root of median nerve from the medial cord and the lateral root of the median nerve from the lateral cord
- Ulnar nerve – medial cord
- Axillary nerve – posterior cord
- Radial nerve – posterior cord
Musculocutaneous nerve
- From the lateral cord of the brachial plexus (C5-C7)
- Enters anterior compartment of arm
- Pierces coracobrachialis (supplies it)
- Passes distally between biceps and brachialis (possible impingement point)
- Terminal branch runs down the lateral aspect of the forearm as the lateral cutaneous nerve of the forearm (supplying skin)
Supplies:
- Muscles of anterior compartment of arm
- Cutaneous (skin) supply- see reference diagram
Lateral root of the median nerve (C6,7)
joins with the medial root of the median nerve to form the median nerve
supplies most of the flexor muscles of forearm
Ulnar nerve (C8-T1)
- Passes through the medial aspect of anterior compartment of arm with the brachial artery
- Passes posterior to the medial epicondyle
- Enters anterior forearm, between the two heads of flexor carpi ulnaris (possible impingement point)
- Passes superficial to the flexor retinaculum
- Passes through the ulnar canal, into the hand (possible impingement point)
Supplies:
-FCU and medial ½ of FDP
-Many muscles in the hand
Abductor DM, Flexor DMB, Opponens DM
Interossei, (palmar & dorsal)
Medial root of the median nerve C8-T1
Joins the lateral root of the median nerve to form the median nerve
Axillary nerve (C5,6)
- Enters posterior aspect of arm via quadrangular space (possible impingement point)
- Winds around surgical neck of humerus where it terminates (possible damage site eg fracture, dislocation)
Supplies:
Deltoid, teres minor
Cutaneous – see reference diagram
Radial nerve (C5,6,7,8,T1)
- Enters the posterior compartment of the arm via lateral triangular space (possible impingement point)
- Runs in the radial/spiral groove (between medial & lateral heads of triceps) with the deep artery of the arm (possible impingement point)
- Passes through lateral aspect of cubital fossa
At the level of the lateral epicondyle it divides into:
- deep branch of radial nerve (muscles & joints)
- superficial branch of radial nerve (cutaneous branch)
- Superficial branch descends through forearm under the brachioradialis muscle
- Runs superficial to anatomical snuffbox
-Deep branch enters the posterior forearm between the two heads of the -supinator muscle (possible impingement point).
Supraclavicular branches (arise superior to the clavicle)
-Dorsal scapular nerve (C5, a little C4)
supplies the rhomboids and levator scapulae
-Long thoracic nerve (C5,6,7)
supplies serratus anterior
-Nerve to subclavius (C5, C6)
supplies subclavius and SC joint
-Suprascapular nerve (C5-6)
supplies supraspinatus, infraspinatus and GH joint
Infraclavicular branches (arise inferior to the clavicle) - Off the lateral cord
-Lateral pectoral nerve (C5,6,7)
supplies pectoralis major
(labelled as lateral thoracic N on the diagram)
-Musculocutaneous nerve (C5,6,7)
supplies the flexor muscles of arm
-Lateral root of the median nerve (C6,7)
joins with the medial root of the median nerve to form the median nerve
supplies most of the flexor muscles of forearm
Infraclavicular branches
- Off the medial cord
-Medial pectoral nerve C8-T1
supplies pectoralis minor and major
-Medial cutaneous nerve of the arm (C8-T1)
skin of medial arm
-Medial cutaneous nerve of the forearm (C8-T1) -
skin of medial forearm
-Ulnar nerve (C8-T1)
Supplies muscles of the anterior (some) forearm and hand (most)
-Medial root of the median nerve (C8-T1)
joins the lateral root of the median nerve to form the median nerve
Infraclavicular branches
- Off the posterior cord
-Upper subscapular nerve (C5)
supplies subscapularis
-Thoracodorsal nerve (C6,7,8)
supplies latissimus dorsi
-Lower subscapular nerve (C6)
supplies teres major & subscapularis
-Axillary nerve (C5,6)
supplies teres minor, deltoid and GH joint
-Radial nerve (C5,6,7,8,T1)
supplies extensor muscles of arm and forearm
Neurological Patterns of the Upper Limb
-Dermatomes – spinal nerve innervation of skin
-Cutaneous/Peripheral nerve supply of skin - via the branches of the
brachial plexus
-Myotomes – motor supply according to spinal levels
Dermatomes
- An area of skin supplied by a single spinal nerve
- useful to determine if a spinal nerve has been damaged
Cutaneous nerve supply
- an area of skin supplied by a single peripheral nerve
- For example an area of skin supplied by a terminal branch of the brachial plexus eg axillary nerve
