Objectives

***to follow

NERVE SUPPLY OF UPPER LIMBS Spinal Nerves = 31 pairs (total)

o Cervical (C) = 8o Thoracic (T)= 12o Lumbar (L)= 5o Sacral (S)= 5o Coccygeal (Co) = 1

Figure 1: Formation of a typical spinal nerve

Components:o Dorsal root (afferent or sensory fibers): formed by

processes of pseudounipolar neuron in dorsal root ganglion

o Ventral root (efferent or motor fibers): formed by axon of neurons on anterior horn and lateral horn (T1 – L2 or L3) of spinal cord

o Spinal nerves formed by the dorsal and ventral roots are mixed nerves, exit through the intervertebral foramina of the vertebral column and divide into dorsal and ventral primary rami

o Dorsal Primary Rami Generally supply deep muscle and skin

of posterior regions of neck and trunk (except C1 and C0)

o Ventral Primary Rami C1-C4

form cervical plexus supply some neck muscles and

parts of skin of head, neck and chest

C5-C8 & T1 form brachial plexus to

supply upper limb

o Myotome The unilateral embryological muscle

mass receiving innervations from a single spinal cord segment or spinal nerve

NOTE: upper limb muscles usually receive motor fibers from several spinal cord segments/nerves

o Dermatome area of the skin supplied by any one

spinal nerve through both its rami dermatomes of consecutive spinal

nerves overlap markedly

Figure 2: Dermatomal distribution of the spinal nerves

I. Cervical Plexus

Figure 3: The cervical plexus

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Somatic plexus formed by the anterior rami of C1-C4 & lies in front of the origins of the Levator scapulae & middle scalene ms

Cutaneous (superficial) & motor (deep) branches

II. Brachial Plexus Somatic plexus formed by the ventral rami of C5-C8 & most

of the ventral rami of T1 Components (from proximal to distal):

Figure 4: The brachial plexus divided into Roots, Trunks, Divisions, Cords & Branches.

ROOTS Primarily ventral rami of spinal nerves C5-T1 Emerge between 2 scalene ms Combines to form 3 trunks Branches:

o Dorsal scapular nerve/DSN (C5): Rhomboids, Levator Scapulae Action: elevation of scapula Deficit: inability to raise arm beyond

horizontal; scapula will also move farther from midline

o Phrenic nerve (C3-C5): Innervates diaphragm

o Long Thoracic nerve/LTN (C5-C7): Serratus Anterior (SA) Paralysis of LTN=

1. Scapular winging: medial border of scapula moves laterally & posteriorly away from the thoracic wall; recall

that the SA holds the scapula against the thoracic wall

2. Inability to perform overhead actions: SA unable to rotate the glenoid cavity superorly

Figure 5: Winging of the (R) scapula due to weakness of SA ms

TRUNKS 3 trunks

o Superior/Upper: C5-C6; Erb’s Point

o Middle: C7o Inferior/Lower: C8

Branches only from superioro Nerve to subclavius:

(supplies) subclaviuso Suprascapular n.:

supraspinatus & infraspinatus

Injury at this area causes: Erb’s Palsy

o Waiter’s Tip positiono Traction of C5-C6 (& occasionally C7) roots during

normal vaginal delivery or landing on the shoulder from a fall

Figure 6: Erb-Duchenne Palsy aka Waiter’s tip deformity d/t traction or tearing of the C5-C6 nerve roots

o Affectation: Musculocutaneous n. Axillary n. Subscapular n.

o Presentation: Arms drooped & in medial rotation;

cannot be raised

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*MnemonicsReally Thirsty? Drink Cold Beer.

No elbow flexion No forearm supination

Klumpke’s Palsyo Claw Hando Traction or avulsion of C8, T1 (& occasionally C7)

roots due to excessive abduction of the armo Presentation:

Forearm supinated Wrist & proximal phalanges

hyperextended Distal phalanges in neutral

Figure 7: Klumpke’s Palsy

DIVISIONS Each Trunk divides into an ANTERIOR (flexor) & POSTERIOR

(extensor) division No terminal branches

CORDS LATERAL CORD

o Branches: Lateral pectoral n.: supplies pectoralis major Musculocutaneous n. Lateral part of Median n.

POSTERIOR CORDo Branches

Superior subscapular n.: supplies subscapularis Thoracodorsal n.

May be due to surgery in the inferior part of the axilla, mastectomies, surgery on scapular lymph nodes

Inability to raise the trunk with the upper limbs (as in climbing)

Will also be unable to use an axillary crutch Inferior subscapular n.: supplies subscapularis &

teres major Axillary n.

May be damaged by compression from incorrect use of axillary crutches (Crutch Palsy) or during intramuscular injection of drugs

Will lead to atrophy of deltoid ms & loss of sensation over the lateral side of the proximal part of the arm

Radial n. Saturday Night Palsy (note right UE)

Figure 8: Saturday Night Palsy due to compression of radial n. at the level of

the spiral groove; results to wrist drop & sensory loss over the dorsum of the

hand & proximal segment of lateral 3 ½ fingers

Radial n. palsy or wrist drop

Figure 9: Wrist drop as a result of Saturday Night Palsy

MEDIAL CORDo Branches:

Medial pectoral n. Medial cutaneous n. of arm Medial cutaneous n. of forearm Medial part of Median n. Ulnar n.

Claw hand deformity/Papal sign

Figure 10: Claw hand deformity or Papal sign due to ulnar nerve involvement. Note guttering of hand due to atrophy of intrinsic ms.

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BRANCHES MUSCULOCUTANEOUS N.

o Motor: Coracobrachialis, biceps brachii & brachialis

o Cutaneous: skin along the lateral border of the forearm through the lateral cutaneous n. of the forearm

MEDIAN NERVEo Motor: ALL muscles in the anterior compartment

of the forearm (except FCU & medial half of FDP), the thenar ms & 2 lateral lumbricals

o Cutaneous: skin over the palmar surface of the lateral 3 ½ digits & over the lateral side of the palm & middle of the wrist

ULNAR NERVEo Motor: FCU, FDP (medial half) & all intrinsic ms of

the hand (except the 3 thenar ms & 2 lateral lumbricals)

o Cutaneous: skin over the palmar surface of the little finger, medial half of the ring finger & skin over the dorsal surface of the medial part of the hand

o Passes through the ulnar or Guyon’s canal at the level of the flexor retinaculum

AXILLARY NERVEo Motor: Deltoids & Teres Minoro Cutaneous: skin over lower 2/3 of Deltoid

RADIAL NERVEo Motor: supplies all muscles of the posterior

compartment of the arm & forearmo Cutaneous: skin over the posterior aspect of the

arm & forearm, lower lateral surface of the arm & the dorsal lateral surface of the hand

Figure 12: Diagram of the brachial plexus showing pathway & innervations. Draw it to know it

Figure 11: Diagram of the cervical plexus showing pathway & innervations. Draw it to know it

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References: Moore, K.L., Dalley, A.F. & Agur, A.M.R. (2010). Clinically

Oriented Anatomy (6th ed.). Snell, R.S. (2004). Clinical Anatomy (7th ed.).

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