GA BRACHIAL PLEXUS pt 2 - anatomy and pathology -

ULNAR NERVE MOTOR:

- flexor carpi ulnaris - flexor digitorum profundus III & IV Motor fibers of the ulnar nerve will continue to travel in the palm as the deep muscular branch.

MEDIAN NERVE

- formed in the axilla by the union of a lateral head (C6 and C7 fibers), arising from the LATERAL CORD with a medial head (C8, T1) arising from the MEDIAL CORD - mixed nerve - C6, C7, C8, T1

ULNAR NERVE C8,T1 anatomy

- no branch in the arm - in the distal arm, it enters a groove between the medial humeral epicondyle and the olecranon process.

AXILLARY NERVE:

- originates in the same place like the subscapularis nerves, - descends on the anterior aspect of the subscapularis muscle, and - winds around the surgical neck of the humerus - passes through the quadrangular space - emerges on the anterior aspect of the humerus - C5,C6 - mixed nerve

MEDIAN NERVE C6,7,8,T1

It descends in the arm on the medial side without giving any branch.

PERIPHERAL MONONEUROPATHIES - SIGNS & SYMPTOMS

The clinical signs and symptoms involve motor, reflex, and sensory disturbances in the entire distribution of each nerve involved.SENSORY: - With the lesion of a sensory/ mixed nerve, ALL sensory modalities are lost/reduced only over the area exclusively supplied by that nerve. MOTOR: - Lesion of a motor or mixed nerve leads to weakness, paresis or paralysis of the muscles innervated by that specific nerve.REFLEX SIGNS: - hyporeflexia /areflexia of the muscles innervated by the affected by the damaged nerve

Cords

The three CORDS enter the axilla above the first part of the axillary artery and approach and embrace its second part. - The cords are named LATERAL, POSTERIOR AND MEDIAL according to their relationship with the second part of the axillary artery

Branches of posterior cord:

UPPER/SUPERIOR SUBSCAPULAR NERVE LOWER/INFERIOR SUBSCAPULAR NERVEMIDDLE SUBSCAPULAR NERVE/THORACODORSAL

MEDIAL CUTANEOUS NERVES LESIONS - SIGNS & SYMPTOMS

SENSORY DEFICIT: - Sensory loss on the medial aspect of the arm - Sensory loss on the medial aspect of the forearm

The dorsal cutaneous branch compression:

SENSORY DEFICIT: - sensory loss on the dorsal ulnar aspect of the hand and dorsal aspect of digit 5 and half of digit 4. The flexor carpi ulnaris and flexor digitorum profundus will be spared.

RADICULOPATHIES - SIGNS & SYMPTOMS

SENSORY: - pain (burning, sharp, well localized). The pain is restricted to a specific dermatome, and is precipitated by maneuvers that cause increased intraspinal pressure.- sensory loss - paresthesia / anesthesia confined to a specific dermatome MOTOR: - weakness/paresis/paralysis in the myotomal distribution of the affected root. REFLEX SIGNS: - hyporeflexia or areflexia in the muscles innervated by the affected spinal root - lesions of the dorsal or ventral root may interrupt the afferent/sensory or efferent/ motor branch of the reflex arc of a specific muscle

Serratus anterior

is segmentally innervated by the LONG THORACIC NERVE fibers Action: - Holds scapula against thoracic wall; Protraction of scapula (PM); Upward rotation of scapula

Divisons

- ANTERIOR DIVISIONS supply the anterior aspect/compartment of the upper extremity (flexor muscles). - POSTERIOR DIVISIONS supply the posterior aspect/compartment of the upper limb (extensor muscles).

RADIAL NERVE:

- C5, C6, C7, C8 - mixed nerve - descends posterior to the axillary artery, - passes through the lower triangular space on the posterior aspect of the humerus

LOWER/INFERIOR SUBSCAPULAR NERVE

- C5,C6 - motor - innervates the subscapularis muscle - inferior part and teres major muscle

UPPER/SUPERIOR SUBSCAPULAR NERVE

- C5,C6 - motor - innervates the subscapularis muscle - superior fibers

MIDDLE SUBSCAPULAR NERVE/THORACODORSAL:

- C6, C7, C8- motor- innervates latissimus dorsi

Axilla Radial nerve injurty - Saturday night palsy

- Inability to extend thumb, proximal phalanges, wrist and elbow - Hand is pronated and the thumb adducted - Total loss of extension of fingers = wrist drop

DORSAL SCAPULAR NERVE MOTOR:

- Levator Scapulae - inferior fibers - Rhomboid minor - Rhomboid major

DORSAL SCAPULAR NERVE

- a branch of C5 root of BP, - contains just motor fibers.

SUPRASCAPULAR NERVE:

- a motor nerve - branch of the upper trunk, - fibers from C5 and C6 spinal nerves

The deep muscular branch of the ULNAR NERVE supplies several muscles:

- abductor digiti minimi - opponens digiti minimi - flexor digiti minimi brevis - interosseous muscles - adductor pollicis - lumbricals III & IV - flexor pollicis brevis (deep head)

SUPRASCAPULAR NERVE INJURY/ENTRAPMENT:

- at the level of the suprascapular foramen or - at the level of the spinoglenoid notch (compression by a ganglionic cyst)

MUSCULOCUTANEOUS NERVE MOTOR:

- coracobrachialis muscle - biceps brachii and - brachialis.

Ulnar nerve injury at the level of the wrist,

- in the Guyon canal, due to a fracture of the pisiform or hamate bone, - entrapment in case of inflammation of the palmar and/or transverse carpal ligaments, or - compression by a ganglion of the carpal joint. MOTOR DEFICIT: - all of the intrinsic muscles innervated by the ulnar nerve will be weak. SENSORY DEFICIT:- on the palmar aspect of the hand and digits

MUSCULOCUTANEOUS NERVE SENSORY:

- lateral antebrachial cutaneous nerve - supplies the lateral aspect of the forearm.

THORACODORSAL NERVE LESIONS - SIGNS & SYMPTOMS:

- little deformity - a combined movement of extension, adduction, and internal rotation, in which the dorsum of the hand is placed on the opposite buttock, reveals the latissimus dorsi deficit.

AXILLARY NERVE LESION - Sensory

- loss of sensation over the shoulder A pure sensory deficit, involving just the lateral brachial cutaneous nerve is possible after nerve lesions during arthroscopic surgery.

MEDIAN NERVE SENSORY:

- median nerve proper will travel in the forearm toward the carpal tunnel. - just proximally to the wrist, it gives a sensory branch that doesn't travel through the carpal tunnel: the palmar branch of median nerve. This innervates the skin over the thenar eminence. - after the median nerve proper pass through the carpal tunnel, other sensory branches of the median nerve will arise. They will innervate the anterior aspect of the palm and digits 1, 2, 3 and half of four, and the dorsal most distal aspect of digits 2nd, 3rd and half of 4th.

MUSCULOCUTANEOUS NERVE

- mixed nerve - terminal branch of lateral cord - contains fibers from C5, C6, and C7 spinal nerves.

ULNAR NERVE

- mixed nerve - terminal branch of medial cord - contains fibers from C8 and T1 roots

LONG THORACIC NERVE

- motor nerve - results through the union of fibers from C5, C6 and C7 roots.

RADIAL NERVE SENSORY:

- posterior brachial cutaneous nerve (in the axilla) - supplies the skin over the posterior aspect of the arm. - posterior antebrachial cutaneous nerve (arises at the level of the spiral groove) - supplies the posterior aspect of the forearm. - superficial branch of radial nerve (at the proximal aspect of the forearm) - travels in the forearm under the brachioradialis, to emerge in the distal forearm. - it will terminate as the dorsal digital nerves, which supply the skin over the lateral aspect of the dorsum of the hand at the level of the first three digits and the dorsum of these digits.

MEDIAN NERVE MOTOR

- superficial, flexor compartment of the forearm - pronator teres, - flexor carpi radialis, - palmaris longus and - flexor digitorum superficialis

SUPRASCAPULAR NERVE: MOTOR:

- supraspinatus - infraspinatus

RADIAL NERVE (mixed) - C5,6,7,8, location

- travels in the spiral groove, together with the deep artery of the arm/deep brachial artery/profundal brachii in close proximity with the bone.

RADIAL NERVE MOTOR:

- two motor branches (while traveling in the spiral groove) - innervate muscles in the posterior compartment of the arm: triceps and anconeus. -> both do elbow extension

UPPER & LOWER SUBSCAPULAR NERVES LESION - SIGNS & SYMPTOMS:

- usually occur with posterior cord lesion MOTOR DEFICIT - the patient will complain of difficulty of scratching the lower back. - the arm is slightly externally rotated, with some difficulties to internally rotate it, although the latissimus dorsi and pectoralis major are able to compensate for it.

1. Radial nerve lesion in the axilla

- windmill pitching MOTOR deficit: - weak flexion of the forearm in a semipronated position - weak elbow extension, - weak extension of the wrist (WRIST DROP) - radial deviation of the wrist, - weak supination MOTOR deficit: - weak extension of metacarpophalangeal joints, - weak extension and abduction of the interphalangeal joints of the pollicis SENSORY deficit: - extensor surface of the arm - extensor surface of the forearm - dorsal aspect of the hand - dorsum of the radial digits

MEDIAN NERVE LESIONS

1. Median nerve lesion in the axilla or arm 2. Median nerve lesion at the elbow 3. Entrapment of median nerve in the forearm MEDIAN NERVE LESIONS - SIGNS & SYMPTOMS Considering that the median nerve doesn't give any branch above the elbow, in any of the described situations the signs and symptoms of the patient will be similar. MOTOR DEFICIT:- paresis/weakness of all the muscles innervated by median nerve. SENSORY DEFICIT:- on the median branches distribution

MUSCULOCUTANEOUS NERVE LESION:

1. Musculocutaneous nerve lesion in the axilla- the most common injury 2. Musculocutaneous nerve entrapment in the substance of coracobrachialis muscle - "carpet-carrier lesion" 3. Musculocutaneous nerve lesion at the level of the elbow (cubital fossa)- rare

BRACHIAL PLEXUS LESIONS:

1. RADICULOPATHIES - a lesion of a spinal nerve or a component (ventral and/or dorsal root of a spinal nerve) - BP roots are affected by lesions at the cervical region level. 2. PLEXOPATHIES - lesions of the plexus (the term "brachial plexopathy" can refer to involvement of the entire plexus or parts of the plexus (trunk, cord, division). - BP trunks are affected by lesions at the first rib level. - BP divisions & cords are affected by lesions at the level of the humerus - ✋😷 different specific plexopathies will be discussed in small group sessions - fairly common 3. PERIPHERAL MONONEUROPATHIES- refer to injuries of an individual peripheral nerve arising from the plexus.

ULNAR NERVE SENSORY:

1. The dorsal cutaneous branch of the ULNAR NERVE - supplies the dorsal ulnar aspect of the hand and - the dorsal aspect of the fifth and half of the 4th digit 2. The palmar branch of the ULNAR NERVE, which - supply the skin over the hypothenar eminence The ulnar nerve proper enters the wrist under the palmar carpal ligament, through the ulnar canal of Guyon. In the hand it gives off a third sensory branch: 3. The superficial branch of the ULNAR NERVE, - supplies the skin of the distal part of the ulnar aspect of the palm and - the palmar aspect of the 5th and half of the 4th digits.

ULNAR NERVE LESIONS

1. Ulnar nerve lesion in the axilla or arm 2. Ulnar nerve lesion at the elbow 3. Entrapment of ulnar nerve in the forearm

MOTOR INNERVATION

A. Shoulder - Supraspinatus & Infraspinatus muscles - Suprascapular nerve- Subscapularis - Upper & lower subscapular nerves- Teres minor & deltoid - Axillary nerve- Teres major - Lower subscapular nerve- Trapezius - CN XI (spinal accessory nerve) & ventral rami C3-C4- Latissimus Dorsi - Middle subscapular / thoracodorsal nerve- Pectoralis Minor - Medial pectoral nerve- Pectoralis Major - Medial pectoral nerve & Lateral pectoral nerve- Levator Scapulae: inferior fibers - Dorsal scapular nerve & superior fibers - ventral rami of C3, C4- Rhomboid Major & Minor - Dorsal Scapular nerve- Serratus anterior - Long thoracic nerve B. Arm Anterior Compartment - Musculocutaneous nervePosterior Compartment - Radial nerve C. Forearm Anterior Compartment - Median nerve branches & Ulnar n. (Flexor carpi ulnaris & medial 1⁄2 of Flexor Digitorum Profundus)Posterior Compartment - Radial nerve D. Hand Intrinsic muscles of the hand - Ulnar nerve & median nerve (Abductor & flexor pollicis brevis; opponens pollicis & 1st & 2nd lumbricals)

SENSORY / CUTANEOUS INNERVATION

A. Shoulder- The skin over the shoulder/clavicle is supplied by - Supraclavicular nerves (C3 & C4 fibers from the cervical plexus) B. Arm- Laterally - Lateral cutaneous nerve of the arm (branch of axillary nerve) Posteriorly - Posterior cutaneous nerve of the arm (branch of radial nerve) Medially & anteriorly - Medial cutaneous brachial nerve (branch of medial cord of brachial plexus) & Intercostobrachial nerve (branch of 2nd intercostal nerve) C. Forearm- Laterally - Lateral cutaneous nerve of the forearm (branch of musculocutaneous nerve)Posteriorly - Posterior cutaneous nerve of the forearm (branch of radial nerve) Medially - Medial cutaneous antebrachial nerve (branch of medial cord of brachial plexus) D. Hand- Anteriorly (palm) - Ulnar nerve & Median nervePosteriorly (dorsum of the hand) - Ulnar nerve & Radial nerve

Terminal branches of posterior cord:

AXILLARY NERVE RADIAL NERVE

LATISSIMUS DORSI

Action: - Arm extension (PM), - Adduction and - Medialrotation.

anterior interosseous nerve - Motor

After passing between the two heads of the pronator teres, the median nerve will give off a pure motor branch, ____________, innervates deep flexor muscles of the forearm - flexor pollicis longus - flexor digitorum profundus I and II - pronator quadratus

APE HAND

Because of the atrophy of the thenar eminence, with retraction of the metacarpal bone of the thumb in the plane of the other metacarpals the hand takes an abnormal appearance called "APE HAND". This results from an unopposed action of extensor pollicis longus and adductor pollicis. When the patient tends to make a fist, the second and the third digits remain extended. The hand then takes the appearance of a clergyman saying the benediction "HAND OF BENEDICTION".

ULNAR NERVE LESIONS - SIGNS & SYMPTOMS

Considering that the ulnar nerve doesn't give any branch above the elbow, in any of the described situations the signs and symptoms of the patient will be similar. MOTOR DEFICIT: - weak flexion and - weak adduction of the wrist, - ULNAR CLAW HAND, in which the 5th and 4th digits are hyperextended at the metacarpophalangeal joints, and flexed at interphalangeal joints. SENSORY DEFICIT: - sensory loss at the level of the ulnar hand

Pectoral nerves

LATERAL PECTORAL NERVE - motor nerve - branch of lateral cord - from C5, C6, C7 spinal nerves MOTOR:- pectoralis major muscle - the clavicular and upper sternocostal fibers MEDIAL PECTORAL NERVE - motor nerve - branch of medial cord - fibers from C8 and T1 spinal segments MOTOR: - pectoralis major muscle - lower sternocostal portion of the pectoralis major muscle - pectoralis minor muscle

LOCALIZATION means to pinpoint "where" is the lesion responsible for a patient's symptoms and signs.

Localization requires an understanding of the anatomy and physiology of the nervous system The process of localization: - begins during history taking, - is refined during the general and neurological examinations, and - is re-assessed after any relevant diagnostic studies are completed

CUTANEOUS NERVE OF THE ARM

MEDIAL BRACHIAL NERVE/MEDIAL CUTANEOUS NERVE OF THE ARM - sensory nerve - branch of medial cord - C8, T1 fibersMEDIAL ANTEBRACHIAL NERVE/MEDIAL CUTANEOUS NERVE OF THE FOREARM - sensory nerve - branch of medial cord - C8, T1 fibers

MEDIAL CUTANEOUS NERVES OF THE ARM (brachial) & FOREARM (antebrachial) - C8,T1

MEDIAL BRACHIAL NERVE/MEDIAL CUTANEOUS NERVE OF THE ARM SENSORY - supplies the skin of the axilla and - the medial aspect of the arm,MEDIAL ANTEBRACHIAL NERVE/MEDIAL CUTANEOUS NERVE OF THE FOREARM SENSORY - conveys to CNS sensory information from the medial skin of the forearm, down to the wrist.

LONG THORACIC NERVE LESIONS - SIGNS & SYMPTOMS:

MOTOR - usually causes no deformity of the scapula when the arm is at rest. - if the patient is asked to push against the wall, scapula becomes winged ("scapula alata")

recurrent nerve

MOTOR In the hand the median nerve gives off several motor branches: - One of these, the _________ innervates the thenar muscles: APB, OP, FPB- superficial head. - Other branches go to the 1st and 2nd lumbricals.

Radial nerve lesion at the level of the humeral shaft

MOTOR & SENSORY deficit similar with lesion in the axilla BUT - the sensibility will be normal on the posterior aspect of the arm, because the posterior brachial nerve branches more proximally, in the axilla - the nerve to the triceps will be spared too

Median nerve entrapment at the level of the carpal tunnel = CARPAL TUNNEL SYNDROME

MOTOR DEFICIT: - appearance of the "APE HAND" SENSORY DEFICIT: - pain and paresthesia at the level of the wrist and hand - Light percussion over the median nerve at the level of the wrist elicits a tingling sensation radiating into the hand in the median distribution "Tinel's sign" ✋😷 The "BENEDICTION SIGN" wouldn't be present due to the fact that the long flexors of the digits are spared.

Radial nerve (deep radial nerve) lesion at the level of the supinator

MOTOR deficit: - all the movements of muscles innervated by the PIN will be deficient, SENSORY deficit: - none (the radial sensory innervation will remain intact)

AXILLARY NERVE LESION - SIGNS & SYMPTOMS

MOTOR deficit: - difficulty in abduction - deltoid atrophy

PECTORAL NERVES LESIONS - SIGNS & SYMPTOMS

MOTOR deficit: - weak adduction of the arm - weak medial rotation of the arm

MUSCULOCUTANEOUS NERVE LESIONS - SIGNS & SYMPTOMS

MOTOR deficit: - weak elbow flexion - weak arm flexion - atrophy of the anterior arm SENSORY deficit: - sensory deficit on the radial aspect of the forearm

AXILLARY NERVE - mixed nerve:

MOTOR: - deltoid and - teres minor SENSORY: - capsule of the shoulder joint - skin of the upper lateral aspect of the arm superficial to the deltoid muscle - lateral brachial cutaneous nerve/lateral cutaneous nerve of the arm

DORSAL SCAPULAR NERVE LESIONS - SIGNS & SYMPTOMS

MOTOR: - lateral displacement of the vertebral border of the scapula and - slight upward rotation.

SUPRASCAPULAR NERVE ENTRAPMENT - SIGNS & SYMPTOMS:

MOTOR: - the resulting deficit will involve both or just infraspinatus muscle, depending where the nerve is entrapped. - weak abduction - Impaired lateral rotation of the arm

CUBITAL FOSSA

Median nerve will travel through the cubital fossa together with brachial artery, biceps tendon, and radial nerve. It could be potentially injured in case of bad venipuncture. Usually the bicipital aponeurosis stops the needle to travel deeper. CUBITAL FOSSA is a V-shape space on the anterior aspect of the elbow. BOUNDARIES: - laterally - brachioradialis - medially - pronator teres - superiorly - an imaginary horizontal plane through the epicondyles of the humerus CONTENT - from lateral to medial: - radial Nerve - biceps tendon - brachial artery - median nerve

RADIAL NERVE MOTOR muscles:

Radial nerve continues to descend, and at the level of the proximal forearm will give motor branches to: - brachioradialis and - extensor Carpi Radialis Longus muscles. The radial nerve continues to descend as the deep radial nerve: - give motor fibers to extensor carpi radialis brevis muscle. - (Keep in mind that there is variation of innervation at this level) - supinator muscle - the posterior interosseus nerve (PIN) - after traveling through the supinator muscle, the deep radial nerve will be in close proximity with the posterior interosseous membrane and will have a new name - it innervates the muscles in the posterior compartment of the forearm: - extensor digitorum - extensor digiti minimi - extensor carpi ulnaris - abductor pollicis longus - extensor pollicis longus - extensor pollicis brevis - extensor indicis

RADIAL NERVE LESIONS - SIGNS & SYMPTOMS

The sensory and/or motor deficit resulting from a lesion will affect all the branches situated distally to the lesion.Please, take a moment to think about the signs and the symptoms of a patient in each case scenario