Brachial Plexus -If you can teach it, you know it! Flashcards
Name the 5 Nerve Roots of the Brachial Plexus.
C5, C6, C7, C8, T1
Name the 5 Terminal Branches of the Brachial Plexus and their Corresponding Cord and Nerve Roots.
Musculocutaneous - Lateral Cord (C5, C6)
Radial - Posterior Cord (C5-T1)
Axillary Posterior Cord (C5-C6)
Median Nerve - Lateral and Medial Cord (C6-T1) (C5?)
Ulnar Nerve - Medial Cord (C8-T1)
Describe the Long Thoracic Nerve
long thoracic nerve is derived from ventral rami of C5, C6, & C7 - close to their emergence from intervertebral foramina;
- it runs downward & pases either in front of or behind middle scalene muscle;
- it reaches upper slip of serratius anterior muscle & descends on outer surface of this muscle, giving branches into it;
Describe the Suprascapular Nerve
suprascapular nerve is derived from upper trunk of brachial plexus, typically receiving fibers from C5 and C6;
- it contains both motor and sensory components, and sends sensory branches to both the glenohumeral and AC joints, but does not innervate the skin;
- it passes downward, laterally (deep to the omohyoid and trapezius & then posteriorly to run under cover of trapezius;
- along with the suprascapular vein and artery, it reaches suprascapular notch;
- the nerve travels beneath the suprascapular notch, where as the vessels travel above the notch;
- after giving off 2 branches to supraspinatus, it passes around lateral border of the scapular spine (spinoglenoid notch and ends in the
- *infraspinatus fossa to supply infraspinatus**);
Lateral Pectoral Nerve
The lateral nerve (lateral anterior thoracic nerve) arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves.
It passes across the axillary artery and vein, pierces the clavipectoral (coracoclavicular) fascia, and is distributed to the deep surface of the Pectoralis major muscle
Name the 3 trunks of the Brachial Plexus and their corresponding nerve roots.
These roots merge to form three trunks:
“superior” or “upper” (C5-C6)
“middle” (C7)
“inferior” or “lower” (C8, T1)
Describe the Dorsal Scapular Nerve
dorsal scapular nerve to both rhomboids is typically derived from C5 neve close to intervertebral foramen and runs downward and backward
thru or across surface of middle scalene, parallel to & below accessory nerve;
- it then passes medial to or thru levator scapulae (to which it may give a branch) and descends on the deep surface of rhomboids, parallel to the
medial border of the scapula
Describe the Lateral Cord of the Brachial Plexus
arises from anterior division of upper (C5, C6) & middle trunks (C7)
- **lateral pectoral nerve
- musculocutaneous nerve**
- lateral root of the median nerve : (FCR & pronator teres) and (sensory fibers to the median nerve)
- lateral cord branches into the musculocutaneous nerve & lateral roots of the median nerve;
- injury to lateral cord impairs elbow flexion (musculocutaneous) and wrist flexion (lateral root of median nerve)
Describe the Medial Cord of the Brachial Plexus
arises from anterior division of lower trunk: C8 & T1;
- medial cord branches into ulnar nerve & the medial root of the median nerve;
- medial pectoral
- medial branchial cutaneous
- medial antebrachial cutaneous
- division of medial cord causes combined median & ulnar nerve deficit
Describe the Posterior Cord of the Brachial Plexus
three posterior divsions of brachial plexus form posterior cord: (C5 , C6 , C7, C8, T1)
- upper subscapular nerve to subscapularis
- thoracodorsal to latissimus dorsi
- lower subscapular nerve to subscapularis and teres major
- axillary nerve
- radial nerve (C5, C6, C7 , C8 , and T1 ) is largest & most frequently injured branch of brachial plexus.
injury to the brachial plexus below the clavicle usually involves cords or peripheral nerves;
- damage to the posterior cord weakens elbow, wrist, and MP joint extension (radial nerve), and shoulder abduction (from axillary nerve)
Describe the Anatomy of Brachial Plexus Injuries
injury to the brachial plexus above clavicle usually involves roots & trunks;
- lesions of C5 / C6 may be caused by widening of head-shoulder interval;
- with brachial plexus injuries, prognosis is guarded but is better w/ C5, C6 injuries;
- when this injury occurs during birth, it produces Erb’s Palsy:
- injured nerves include: axillary, musculocutaneous, and suprascapular;
- traction injuries are most common at C5 and C6 levels;
- proximal cord lesions will injure supraclavicular branches + distal plexus and will lead to winging of scapula
Describe the Anatomy of Obstetricial Palsy: Lower Root Injury: (Klumpke)
injury to the lower roots (C8 and T1 ) & or C7;
- may follow forceful abduction of shoulder, produces weakness in intrinsics of hand as well as long flexors & extensors of the fingers;
- *C4-C7 roots are well secured to their respective vertebrae & are less prone to avulsion areas**;
- C8 and T1 roots are not well secured
Describe an Upper Trunk Brachial Plexus Injuries
upper trunk brachial plexus injuries are common football tackling injuries, which may be refered to as “stingers;”;
- named for temporary sensation that radiates from the shoulder to the hand;
- most often involves C5 and C6 nerve roots, which make up the upper trunk of the brachial plexus
- occurence of 65% of collegiate football players during 4-year career
- often go unreported - most episodes last seconds to minutes
- 5-10% of cases, neurologic deficit may last hours, days, or weeks
player should not return to competition if he has weakness of shoulder abductors and external rotators as well as biceps weakness;
neck pain or has motor weakness
Describe the Axillary Nerve
- *axillary nerve (C5, C6)** originates from and passes backward from posterior cord of brachial plexus - at level of axilla;
- after passing thru quadrilateral space (at inferior border of subscapularis muscle and posterior aspect of the humeral neck) it divides into
- *anterior and posterior trunks;**
- anterior trunk:
- branches supply the middle and anterior deltoid as it winds around the inner surface of deltoid;
- posterior trunk:
- *- branch to the teres minor muscle
- posterior part of the deltoid muscle (lie deep in deltoid);
- terminal branches: superior lateral brachial cutaneous nerve**
Describe the Median Nerve
roots: C6, C7, C8, and T1 (?C5)
- lateral cord: contributes mainly sensory axons from C6 and C7
- medial cord: provides main bulk of motor input through C8 and T1
- position in the arm:
- has no branches in arm;
- crosses brachial artery from lateral to medial in the arm, then passes over brachialis;
- median nerve is parallel and anterior to the medial intermuscular septum
Desribe the Medial Antebrachial Cutaneous Nerve
- *innervation: (C8, T1);**
- medial antebrachial cutaneous nerve descends in the arm anterior and medial to brachial artery;
- at distal to mid forearm level, nerve emerges from under brachial fascia adjacent to basilic vein;
- it innervates the skin of anterior & medial surfaces of forearm as far as wrist;
- nerve divides into 1-3 branches above the elbow as it travels to the medial epicondyle and olecranon;
- these nerve branches may pass either proximal or distal to the epicondyle;
Describe the Anterior Interosseous Branch of the Median Nerve
arises from median nerve, 5 cm above medial epicondyle;
- runs on volar surface of FDP and along interosseous membrane between ulna & radius;
- supplies FPL, lateral half of FDP, & pronator quadratus;
- may supply sensory branches carpal joints;
AIN is principally a motor nerve;
- it arises from median nerve at a variable point as it passes between two heads of the pronator teres, descends vertically in front of interosseous membrane between
- *FDP & FPL**, supply these 2 muscles, & finally terminates in pronator quadratus near wrist joint;
- it divides from the median nerve 4 to 6 cm below the elbow;
Describe the Posterior Cord of the Brachial Plexus
- *three posterior divsions of brachial plexus form posterior cord: (C5 , C6 , C7, C8, T1)**
- upper subscapular nerve to subscapularis
- thoracodorsal (C6-8) to latissimus dorsi
- lower subscapular nerve (C5-6) to subscapularis and teres major
- axillary nerve
- radial nerve (C5, C6, C7 , C8 , and T1 ) is largest & most frequently injured branch of brachial plexus
Describe the Radial Nerve
three posterior divsions of brachial plexus form posterior cord: (C5 , C6 , C7, C8, T1)
- radial nerve (C5, C6, C7 , C8 , and T1 ) is largest of & most frequently injured branch of both the posterior cord (as well as the brachial plexus);
- in axilla, it gives off:
- posterior cutaneous nerve of arm;
- branch to long & medial heads of triceps;
- between axilla & spiral groove of humerus:
- it distributes a branch to the lateral head of the triceps;
nerve travels from deep to the lateral head of the triceps, piercing the intermuscular septum;
- after piercing lateral intermuscular septum, the nerve comes to lie between the brachialis and brachioradialis, and
goes on to pass in front of elbow:
- radial nerve emanates from the spiral groove approximately 10 cm proximal to the lateral epicondyle;
- branch to brachioradialis & ECRL ;
- nerve remains anterior relative to the humerus, and passes along the lateral column of the distal humerus
Describe the Posterior Interosseous Nerve
it divides from radial nerve in front of radial head, passes between the superficial and deep heads of the supinator, w/ deep branch (PIN) passing backward thru
supinator (arcade of Froshe) to supply 9 muscles on extensor aspect of forearm;
- because of the numerous branches into which the deep radial nerve breaks up at the lower border of the supinator, surgical
repair of the nerve here is difficult;
- remaining part PIN, runs downward parallel to posterior interosseous artery to supply all of deeper lying extensor muscles
& ends as a twig to wrist joint;
- superficial portion innervates ECU, EDC, and extensor digiti minimi;
- deep branch: innervates APL, EPB, EPL, and extensor indicis proprius;
- in this course, it passes superficial to long abductor & EPB of thumb, but its terminal branch to wrist joint passes deep to EPL & EIP;
- sensory branch:
- superficial branch of radial nerve passes into forearm deep to brachioradialis muscle;
- approx 8 cm from tip of radial styloid, nerve emerges from under tendon of BR between tendon of BR & tendon of ECRL;
- sensory branch passes downward emerging dorsally from beneath BR tendon about 5 cm proximal to radial styloid;
- it lies just deep to the superficial veins;
- distally, it provides sensation to dorsum of thumb, excluding subungual region which is supplied by branches of median;
- superficial branch innervates dorsal aspect of first web space & hand as far ulnarward as middle of ring finger & as far distally
as proximal interphalangeal joint.
