5. Nerves of the upper limb

Origination of median nerve

1) one of the 5 main nerves originating from the brachial plexus 2) It originates from the lateral and medial cords of the brachial plexus 3) lateral root - lateral cord of the brachial plexus medial root - medial cord of the brachial plexus

Nerves of the Upper Limb (5 main nerves arise from brachial plexus)

1. Brachial plexus 2. Axillary nerve 3. Musculocutaneuous nerve 4. Radial nerve 5. Median nerve 6. Ulnar nerve

Motor functions of axillary nerve

Abduction of arm at shoulder beyond first 15 degrees

Ulnar nerve course #1

After arising from the brachial plexus, the ulnar nerve descends in a plane between the axillary artery (lateral) and the axillary vein (medial). It proceeds down the medial aspect of the arm with the brachial artery located lateral. At the mid-point of the arm, the ulnar nerve penetrates the medial fascial septum to enter the posterior compartment of the arm. It passes posterior to the elbow through the ulnar tunnel (small space between the medial epicondyle and olecranon). Here, it also gives arise to an articular branch which supplies the elbow joint. In the forearm, the ulnar nerve pierces the two heads of the flexor carpi ulnaris, and travels deep to the muscle, alongside the ulna.

Anatomical course of median nerve

After originating from the brachial plexus in the axilla, the median nerve descends down the arm, initially lateral to the brachial artery. Halfway down the arm, the nerve crosses over the brachial artery, and becomes situated medially. The median nerve enters the anterior compartment of the forearm via the cubital fossa. In the forearm, the nerve travels between the flexor digitorum profundus and flexor digitorum superficialis muscles. The median nerve gives off two major branches in the forearm:

Divisions of Brachial Plexus

All of them - anterior and posterior

Anterior interosseous nerve

Branch of the median nerve that supplies the deep muscles on the anterior of the forearm

Roots of Brachial Plexus

C5, C6, C7, C8, T1

Radial nerve originates from...

C5, C6, C7, C8, T1 Posterior cord

Median nerve roots

C6 - T1 (also contains fibres from C5 in some individuals)

Cutaneuos innervation of the axillary nerve

Cutaneuos innervation: Superior lateral brachial cutaneous nerve Carry information from the shoulder joint Skin covering inferior region of deltoid muscles

Median nerve palsy

Damage to median nerve usually in carpal tunnel

Motor functions of the Ulnar Nerve

Finger adduction and abduction other than thumb; thumb adduction, flexion of digits 4&5, wrist flexion and adduction

Motor functions of the Musculocutaneous Nerve

Flexion of arm at elbow, supination of forearm

Axillary nerve paralysis

Frequently injured due to shoulder dislocation because of the proximity of this joint Paralysis of the deltoid and teres minor - it results in weakness of the arm abduction Sensory functions - the upper lateral cutaneous nerve of arm will be affected, resulting in loss of sensation over the inferior deltoid ('regimental badge area').

Axillary nerve

From root C5-C6 Arise from posterior cord of brachial plexus at the level of axilla

Muscular branch of ulnar nerve

Innervates flexor carpi ulnaris and flexor digitorum profundus (medial half)

Ulnar nerve origin

It originates from the C8-T1 nerve roots (and occasionally carries C7 (fibres) which form part of the medial cord of the brachial plexus

Three main branches arise in the forearm:

Muscular branch Palmar cutaneous branch Dorsal cutaneous branch

Muscular innervations of the axillary nerve

Muscular innervations: Anterior branch → anterior and lateral fiber of deltoid muscles Posterior branch → teres minor and posterior fiber of deltoid

Brachial plexus

Networking of spinal nerves, formed by ventral (anterior rami) of cervical spinal nerves C5-C8 and thoracic spinal nerves T1 It is responsible for cutaneous (sensory) and muscular (motor) innervation of the entire upper limb

Sensory functions of the Median Nerve

Palmar cutaneous branch - arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome. Palmar digital cutaneous branch - arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.

It can be classified by specific local causes, including:

Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, tight anterior scalene muscles Problems originating in the chest: tight pectoralis minor muscles Brachial plexus abnormalities Elbow pathology: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers Forearm pathology: tight flexor carpi ulnaris muscles Wrist pathology: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome

Musculocutaneous nerve arise from..

Root C5, C6 and C7 Lateral cord Opposite to the lower border of pertoralis minor

Axillary Nerve (sensory functions)

Sensory functions → skin over the shoulder

Trunks of Brachial Plexus

Superior (C5-C6) Middle (C7) Inferior (C8-T1)

The Quadrangular Space

Superior - inferior aspect of teres minor Inferior - superior aspect of teres major Lateral - surgical neck of humerus. Medial - long head of triceps brachii Anterior - subscapularis

Course of axillary artery

The axillary nerve is formed within the axilla area of the upper limb. It is a direct continuation of the posterior cord from the brachial plexus - and therefore contains fibres from the C5 and C6 nerve roots. In the axilla, the axillary nerve is located posterior to the axillary artery and anterior to the subscapularis muscle. It exits the axilla at the inferior border of subscapularis via the quadrangular space, often accompanied by the posterior circumflex humeral artery and vein.

Anatomical course of axillary artery and its branches

The axillary nerve then passes medially to the surgical neck of the humerus, where it divides into three terminal branches: Posterior terminal branch - provides motor innervation to the posterior aspect of the deltoid muscle and teres minor. It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm. Anterior terminal branch - winds around the surgical neck of the humerus and provides motor innervation to the anterior aspect of the deltoid muscle. It terminates with cutaneous branches to the anterior and anterolateral shoulder. Articular branch - supplies the glenohumeral joint

Motor innervations of ulnar nerve in the hand

The majority of the intrinsic hand muscles are innervated by the deep branch of the ulnar nerve: Hypothenar muscles (flexor digiti minimi brevis, abductor digiti minimi, opponens digiti minimi) Medial two lumbricals Adductor pollicis Palmar and dorsal interossei of the hand

Anatomical course of musculocutaneous nerve

The musculocutaneous nerve is the terminal branch of the lateral cord of the brachial plexus (C5, C6 and C7) and emerges at the inferior border of pectoralis minor muscle. It leaves the axilla and pierces the coracobrachialis muscle near its point of insertion on the humerus. It gives a branch to this muscle. The musculocutaneous nerve then passes down the flexor compartment of the upper arm, superficial to brachialis but deep to the biceps brachii muscle. It innervates both these muscles and gives articular branches to the humerus and the elbow. The nerve then pierces the deep fascia lateral to biceps brachii to emerge lateral to the biceps tendon and brachioradialis. It continues into the forearm as the lateral cutaneous nerve and provides sensory innervation to the lateral aspect of the forearm.

In the hand, via the superficial branch of ulnar nerve

The palmaris brevis is an exception to this rule and is innervated by the superficial branch of the ulnar nerve. The other muscles of the hand (lateral two lumbricals and the thenar eminence) are innervated by the median nerve.

Course of radial nerve

The radial nerve is the terminal continuation of the posterior cord of the brachial plexus. It therefore contains fibres from nerve roots C5 - T1. The nerve arises in the axilla region, where it is situated posteriorly to the axillary artery. It exits the axilla inferiorly (via the triangular interval), and supplies branches to the long and lateral heads of the triceps brachii. The radial nerve then descends down the arm, travelling in a shallow depression within the surface of the humerus, known as the radial groove. As it descends, the radial nerve wraps around the humerus laterally, and supplies a branch to the medial head of the triceps brachii. During much of its course within the arm, it is accompanied by the deep branch of the brachial artery. To enter the forearm, the radial nerve travels anterior to the lateral epicondyle of the humerus, through the cubital fossa. The nerve then terminates by dividing into two branches: Deep branch (motor) - innervates the muscles in the posterior compartment of the forearm. Superficial branch (sensory) - contributes to the cutaneous innervation of the dorsal hand and fingers.

Sensory Functions of radial nerve

There are four branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb. Three of these branches arise in the upper arm: Lower lateral cutaneous nerve of arm - Innervates the lateral aspect of the arm, inferior to the insertion of the deltoid muscle. Posterior cutaneous nerve of arm - Innervates the posterior surface of the arm. Posterior cutaneous nerve of forearm - Innervates a strip of skin down the middle of the posterior forearm. The fourth branch - the superficial branch - is a terminal division of the radial nerve. It innervates the dorsal surface of the lateral three and half digits and the associated area on the dorsum of the hand.

Motor function of the Median Nerve

Thumb flexion and opposition, Flexion of digits 2&3, Wrist flexion and abduction, Forearm pronation

Sensory functions of the Ulnar Nerve

Two of these branches arise in the forearm, and travel into the hand: Palmar cutaneous branch - innervates the medial half of the palm. Dorsal cutaneous branch - innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area. The last branch arises in the hand itself: Superficial branch - innervates the palmar surface of the medial one and a half fingers.

Common palmar digital branch of median nerve

lateral 2 lumbricals of the hand

Cords of Brachial Plexus

lateral, posterior, medial (based off where they're located related to axillary artery)

Musculocutaneous nerve muscular innervations

penetrate coracobrachialis and pass obliquely between biceps brachii (anterior) and the brachialis (deep) to the lateral side of the arm BBC

Structure of Brachial Plexus

roots, trunks, divisions, cords, branches Ragbi Teams Drink Cold Beverages

Palmar cutaneous branch of ulnar nerve

sensory to medial palm, cutaneous innervation to the anterior skin and nails

Median nerve is the only nerve that passes through..

the carpal tunnel

Musculocutaneous nerve cutaneous innervations then continue..

then continues in the forearm as the lateral antebrachial cutaneous nerve

In the hand, the nerve terminates by giving rise to:

to superficial and deep branches.

Articular branches of median nerve..

branches distributed to joints to the elbow, wrist, carpal and phalangeal joints

Carpal tunnel syndrome

Compression medial nerve at the carpal tunnel Patient will experience numbness, tingling, or burning sensation at the thumb, index, middle and radial half of the ring finger If untreated - weakness or atrophy of the thenar muscles

Lesions of the Median Nerve

Damaged at the Elbow Mechanism of injury: Supracondylar fracture of the humerus. Motor functions: The flexors and pronators in the forearm are paralysed, with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus. The forearm constantly supinated, and wrist flexion is weak (often accompanied by adduction, because of the pull of the flexor carpi ulnaris).Flexion at the thumb is also prevented, as both the longus and brevis muscles are paralysed. The lateral two lumbricals are affected, and the patient will not be able to flex at the MCP joints or extend at IP joints of the index and middle fingers. Sensory functions: Lack of sensation over the areas that the median nerve innervates. Characteristic signs: The thenar eminence is wasted, due to atrophy of the thenar muscles. If patient tries to make a fist, only the little and ring fingers can flex completely. This results in a characteristic shape of the hand, known as hand of benediction. Damaged at the Wrist Mechanism of injury: Lacerations just proximal to the flexor retinaculum. Motor functions: Thenar muscles paralysed, as are the lateral two lumbricals. This affects opposition of the thumb and flexion of the index and middle fingers. Sensory functions: Same as an injury at the elbow. Characteristic signs: The hand is held in the same position as damage at the elbow, but the forearm is unaffected (not supinated or adducted, wrist flexion likely unaffected, depending on the location of the lesion).

Injury to the Radial Nerve

In the Axilla: The radial nerve can be damaged in the axilla region by a dislocation at the shoulder joint, or a fracture of the proximal humerus. Occasionally, it is injured via excessive pressure on the nerve within the axilla (e.g. a badly fitting crutch). Motor functions - the triceps brachii and muscles in posterior compartment are affected. The patient is unable to extend at the forearm, wrist and fingers. Unopposed flexion of wrist occurs, known as wrist-drop. Sensory functions - all four cutaneous branches of the radial nerve are affected. There will be a loss of sensation over the lateral and posterior arm, posterior forearm, and dorsal surface of the lateral three and a half digits. In the Radial Groove: The radial nerve is tightly bound within the spiral groove of the humerus. Thus, it is most susceptible to damage with a fracture of the humeral shaft. Motor functions - The triceps brachii may be weakened, but is not paralysed (branches to the long and lateral heads of the triceps arise proximal to the radial groove).Muscles of the posterior forearm are affected. The patient is unable to extend at the wrist and fingers. Unopposed flexion of wrist occurs, known as wrist-drop. Sensory functions - the cutaneous branches to the arm and forearm have already arisen. The superficial branch of the radial nerve will be damaged, resulting in sensory loss to the dorsal surface of the lateral three and half digits and the associated area on the dorsum of the hand.

Motor innervations of ulnar nerve in the anterior forearm:

In the anterior forearm, the muscular branch of the ulnar nerve supplies two muscles: Flexor carpi ulnaris - flexes and adducts the hand at the wrist. Flexor digitorum profundus (medial half) - flexes the ring and little fingers at the distal interphalangeal joint The remaining muscles in the anterior forearm are innervated by the median nerve.

Carpal tunnel

In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the hand.

Ulnar entrapment

It is a condition where the ulnar nerve becomes trapped or pinched due to some physiological abnormalities It is classified by location of entrapment The ulnar nerve passes through several small tunnels and outlets through the medial upper extremity, and at these points the nerve is vulnerable to compression or entrapment - a so-called "pinched nerve„ The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy

Median nerve palsy - signs and symptoms:

Lack of ability to abduct and oppose the thumb due to paralysis of the thenar muscles. This is called "ape-hand deformity„ Sensory loss in: the thumb, index finger, long finger, and the radial aspect of the ring finger Weakness in: forearm pronation wrist and finger flexion Difficulties in Activities of daily living (ADL) such as brushing teeth, tying shoes, making phone calls, turning door knobs and writing

Lateral antebrachial cutaneous

Lateral antebrachial cutaneous nerve divide into anterior and posterior branches: Anterior branch - skin of anterolateral surface of forearm as far as ball of the thumb Posterior branch - skin of posterolateral surface of forearm

Superior lateral brachial cutaneous nerve

Location along lower posterior border of deltoid muscle Supplies skin of upper lateral aspect of arm Is the continuation of the posterior branch of the axillary nerve, after it pierces the deep fascia. Carry information from the shoulder joint Skin covering inferior region of deltoid muscles

Clinical Relevance: Ulnar Nerve Palsy (Damage at the Wrist)

Mechanism of injury: Lacerations to the anterior wrist. Motor functions: Only the intrinsic muscles of the hand are affected. Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei). Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles). Adduction of the thumb is impaired, and the patient will have a positive Froment's sign (due to paralysis of adductor pollicis). Sensory functions: The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected. This results in sensory loss over palmar side of medial one and a half fingers only. Characteristic signs: Patient cannot grip paper placed between fingers, positive Froment's sign, wasting of hypothenar eminence.

Clinical Relevance: Ulnar Nerve Palsy (Damage at the Elbow)

Mechanism of injury: Trauma at the level of the medial epicondyle (e.g. isolated medial epicondyle fracture, supracondylar fracture). It can also be compressed in the cubital tunnel. Motor functions: All the muscles of innervated by the ulnar nerve are affected. Flexion of the wrist can still occur, but is accompanied by abduction (due to paralysis of flexor carpi ulnaris and medial half of flexor digitorum profundus). Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei). Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles). Adduction of the thumb is impaired, and the patient will have a positive Froment's sign (due to paralysis of adductor pollicis). Sensory functions: All sensory branches are affected, so there will be a loss of sensation over the areas that the ulnar nerve innervates. Characteristic signs: Patient cannot grip paper placed between fingers, positive Froment's sign, wasting of hypothenar eminence.

After giving off the anterior interosseous and palmar cutaneous branches...

The median nerve enters the hand via the carpal tunnel - where it terminates by dividing into two branches: Recurrent branch - innervates the thenar muscles. Palmar digital branch - innervates the palmar surface and fingertips of the lateral three and half digits. Also innervates the lateral two lumbrical muscles.

Major branches of Median Nerve

The median nerve gives off two major branches in the forearm: Anterior interosseous nerve - supplies the deep muscles in the anterior forearm. Palmar cutaneous nerve - innervates the skin of the lateral palm

Motor Functions of radial nerve

The radial nerve innervates the muscles located in the posterior arm and posterior forearm. In the arm, it innervates the three heads of the triceps brachii, which acts to extend the arm at the elbow. The radial nerve also gives rise to branches that supply the brachioradialis and extensor carpi radialis longus (muscles of the posterior forearm). A terminal branch of the radial nerve, the deep branch, innervates the remaining muscles of the posterior forearm. As a generalisation, these muscles act to extend at the wrist and finger joints, and supinate the forearm. Note: When the deep branch of the radial nerve penetrates the supinator muscle of the forearm, it is termed the posterior interosseous nerve for the remainder of its course.

Anterior interosseous nerve supplies..

all the flexor muscles of the forearm; (flexor carpi radialis, pronator teres, palmaris longus, flexor digitorium superificialis, flexor digitorium profundus, pronator quadratus) apart from flexor carpi ulnaris (ulnar nerve) and the ulnar half of flexor digitorum profundus (ulnar)

Dorsal cutaneous branch of ulnar nerve

cutaneous innervation to the dorsal medial hand and the dorsum of the medial 1.5 fingers

Palmar cutaneous branch

cutaneous innervation to the palmar passes over flexor retinaculum aspect of the thumb, index and middle fingers and the radial half of the ring finger

Superficial/deep branch of Ulnar nerve

divides immediately distal to the pisiform bone superficial branch - mainly sensory function deep branch - mainly motor functions

Course of Median Nerve

laterally - to the axillary artery; descends - in the arm between biceps brachii and triceps brachii muscles courses - through the forearm with the ulna nerve and vessels, before entering the carpal tunnel to the hand