Brachial Plexus Update PDF

BRACHIAL PLEXUS AND ITS APPLIED ANATOMY  INTRODUCTION ❖ The Brachial Plexus is a complex network of nerves that supplies motor and sensory innervation to the upper limb (shoulder, arm, forearm, and hand). ❖ It begins/arise from the spinal cord, through the cervico...

BRACHIAL PLEXUS AND ITS APPLIED ANATOMY  INTRODUCTION ❖ The Brachial Plexus is a complex network of nerves that supplies motor and sensory innervation to the upper limb (shoulder, arm, forearm, and hand). ❖ It begins/arise from the spinal cord, through the cervicoaxillary canal in the neck, over the first rib, and extends into the axilla (armpit).  Brachial Plexus Structure ❖ The brachial plexus is divided into: ✔ Five (5) roots, ✔ Three (3) trunks ✔ six (6) divisions ❑ Three (3) anterior and three (3) posterior ✔ three cords, and ✔ five branches.  ROOTS The ‘roots’ refer the beginning of the brachial plexus. The five roots are the five anterior rami, which forms the spinal nerves C5, C6, C7, C8 and T1. At each vertebral level, paired spinal nerves arise.  TRUNKS. At the base of the neck, the roots of the brachial plexus converge to form three trunks. Superior trunk – a combination of C5 and C6 roots. Middle trunk – continuation of C7. Inferior trunk – combination of C8 and T1 roots.  DIVISIONS Each trunk divides/splits into two branches within the posterior triangle of the neck to form six divisions. One division moves anteriorly (toward the front of the body) and the other posteriorly (towards the back of the body).  CORDS ❖ These six divisions regroup to become the three cords or large fiber bundles. ❖ The cords are named by their position with respect to the axillary artery. ❖ These cords are lateral cord, posterior cord and medial cord. Lateral Cord (from anterior divisions of superior and middle trunks) Posterior Cord (from all posterior divisions) Medial Cord (from the anterior division of the inferior trunk)  BRANCHES ❖ There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches ❖ Branches: these include several important nerves: Musculocutaneous nerve (from the lateral cord) Axillary nerve (from the posterior cord) Radial nerve (from the posterior cord) Median nerve (from both lateral and medial cords) Ulnar nerve (from the medial cord)  Anatomy of the Musculocutaneous Nerve 1. Origin: root value: C5, C6, and C7 spinal nerve roots. 2. Motor Function: innervates the following muscles in the anterior compartment of the arm: Coracobrachialis: Assists in flexion and adduction of the arm at the shoulder. Biceps Brachii: forearm flexion and supination (rotation of the forearm so that the palm faces upward). Brachialis: A powerful flexor of the forearm at the elbow. 3. Sensory Function: the musculocutaneous nerve continues as the lateral cutaneous nerve of the forearm, which supplies sensation to the lateral aspect of the forearm. Clinical Significance: musculocutaneous nerve Injury to the musculocutaneous nerve is rare, but it can result in weakened flexion and supination of the forearm, as well as sensory loss over the lateral forearm. It may be injured in cases of trauma or in rare cases of compression in the axilla.  ANATOMY OF THE AXILLARY NERVE 1. Origin: The axillary nerve arises from the posterior cord of the brachial plexus, with contributions from the C5 and C6 spinal nerve roots. 2. Course: After its origin, the axillary nerve passes through the quadrangular space (bounded by the teres minor, teres major, long head of the triceps, and humerus). It then winds around the surgical neck of the humerus, making it vulnerable to injury in this region (e.g., in fractures of the surgical neck of the humerus). 3. Motor Function: The axillary nerve provides motor innervation to two key muscles in the shoulder: Deltoid muscle: Responsible for abduction of the arm at the shoulder beyond 15 degrees. Teres minor muscle: Assists in lateral rotation of the arm at the shoulder. 4. Sensory Function: The axillary nerve gives off the superior lateral cutaneous nerve of the arm, which supplies sensation to the skin over the deltoid (the shoulder area).  Clinical Significance: Injury to the axillary nerve is commonly seen in fractures of the surgical neck of the humerus or anterior shoulder dislocations. – Motor deficits: Patients with axillary nerve damage may have difficulty abducting their arm due to weakness or paralysis of the deltoid. – Sensory deficits: There may be sensory loss or altered sensation over the "regimental badge" area (the skin over the deltoid). Quadrangular space syndrome can also compress the axillary nerve, leading to pain and weakness in the shoulder.  Anatomy of the Median Nerve 1. Origin: originates from the union of the lateral cord (C5, C6, C7) and the medial cord (C8, T1). 2. Motor Function: major muscles innervated by the median nerve: ▪ Forearm: Pronator teres: Pronates the forearm. Flexor carpi radialis: Flexes and abducts the wrist. Palmaris longus: Flexes the wrist. Flexor digitorum superficialis: Flexes the middle phalanges of the fingers. Flexor pollicis longus: Flexes the thumb. Pronator quadratus: Pronates the forearm. ▪ Hand: – Opponens pollicis: Opposes the thumb. – Abductor pollicis brevis: Abducts the thumb. – Flexor pollicis brevis (superficial head): Flexes the thumb. – Lumbricals (1st and 2nd): Flexes the metacarpophalangeal joints and extends the interphalangeal joints of the index and middle fingers. 4. Sensory Function: the median nerve provides sensory innervation to: – The palmar surface of the lateral three and a half fingers (thumb, index, middle, and half of the ring finger). – The dorsal tips of these fingers (over the distal phalanges).  Clinical Significance Carpal Tunnel Syndrome: It occurs when the nerve is compressed as it passes through the carpal tunnel in the wrist, leading to symptoms like pain, numbness, tingling, and weakness in the thumb and lateral fingers. Hand of Benediction: This occurs when the median nerve is damaged at the elbow or forearm level. When attempting to make a fist, the patient cannot flex the index and middle fingers, leaving the hand partially open (in a "benediction" posture). Anterior Interosseous Nerve Syndrome: The anterior interosseous branch of the median nerve can become compressed, leading to difficulty in performing the "OK sign" due to weakness in the flexor pollicis longus and the flexor digitorum profundus of the index finger.  Anatomy of the Radial Nerve 1. Origin: arises from the posterior cord of the brachial plexus, with contributions from the C5–T1 nerve roots. 2. Branches and Motor Function: Upper Arm: – Triceps brachii: Extends the forearm at the elbow. – Anconeus: Assists in extension of the forearm and stabilizes the elbow joint. Forearm: The radial nerve divides into two terminal branches in the forearm: Superficial branch: Primarily sensory. Deep branch (Posterior Interosseous Nerve): Motor innervation Muscles innervated by the deep branch: – Brachioradialis: Flexes the forearm at the elbow, particularly when the forearm is in a mid-pronation position. – Extensor carpi radialis longus and brevis: Extend and abduct the wrist. – Extensor digitorum: Extends the fingers. – Extensor carpi ulnaris: Extends and adducts the wrist. – Supinator: Supinates the forearm. – Abductor pollicis longus: Abducts the thumb. – Extensor pollicis brevis: Extends the thumb at the metacarpophalangeal joint. – Extensor pollicis longus: Extends the thumb at both the metacarpophalangeal and interphalangeal joints. – Extensor indicis: Extends the index finger. 4. Sensory Function: ❖ The radial nerve provides sensory innervation to: Posterior aspect of the arm: via the posterior cutaneous nerve of the arm. Posterior aspect of the forearm: via the posterior cutaneous nerve of the forearm. Dorsal aspect of the hand: The superficial branch of the radial nerve provides sensation to the lateral half of the dorsum of the hand, including the proximal parts of the lateral three and a half digits (not including the nail beds, which are innervated by the median nerve).  Clinical Significance: Radial Nerve Palsy: – This condition is often caused by trauma to the radial nerve, especially in fractures of the humeral shaft (due to the nerve's proximity to the radial groove). – Wrist Drop is a classic sign of radial nerve injury, resulting in an inability to extend the wrist and fingers. This happens because the extensors in the forearm are paralyzed. Saturday Night Palsy: This can occur when the radial nerve is compressed for an extended period, such as when an individual falls asleep with their arm draped over a chair, causing temporary paralysis.  Anatomy of the Ulnar Nerve 1. Origin: originates from the medial cord of the brachial plexus, with nerve roots from C8 and T1 (and sometimes C7). 2. Branches and Motor Function: ❖ Forearm: innervates two muscles in the anterior compartment of the forearm: Flexor carpi ulnaris: Flexes and adducts the wrist. Medial half of the flexor digitorum profundus: Flexes the distal phalanges of the little and ring fingers (digits 4 and 5). ❖ Hand: innervates many of the intrinsic muscles of the hand. ▪ Hypothenar muscles (muscles of the little finger): – Abductor digiti minimi: Abducts the little finger. – Flexor digiti minimi brevis: Flexes the little finger. – Opponens digiti minimi: Opposes the little finger. ▪ Interossei muscles: – Dorsal interossei: Abduct the fingers. – Palmar interossei: Adduct the fingers. ▪ Lumbricals (medial two): Flex the metacarpophalangeal joints and extend the interphalangeal joints of the ring and little fingers. ▪ Adductor pollicis: Adducts the thumb. ▪ Deep head of the flexor pollicis brevis: Helps to flex the thumb. 3. Sensory Function: The ulnar nerve provides sensory innervation to: Medial side of the hand: – The palmar surface: Sensory innervation to the skin of the little finger and the medial half of the ring finger. – The dorsal surface: The medial half of the dorsum of the hand, including the skin over the little finger and part of the ring finger.  Clinical Significance Ulnar Nerve Entrapment: – The ulnar nerve is prone to compression, especially at the elbow in the cubital tunnel or at the wrist in Guyon’s canal. Claw Hand: is a deformity characterized by the hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints in the fingers. Froment's Sign: – A test used to assess ulnar nerve function. – The patient is asked to hold a piece of paper between the thumb and index finger. – If the ulnar nerve is damaged, the adductor pollicis will be weak, and the patient compensates by using the flexor pollicis longus (innervated by the median nerve), causing flexion at the thumb’s interphalangeal joint.  ERB’S PALSY (RUPTURE) ❖ Erb's palsy or Erb–Duchenne palsy is a paralysis of the arm caused by injury to the upper group of the arm's main nerves, specifically the severing of the upper trunk C5–C6 nerves. ❖ Erb’s palsy is often referred to as another name for BPP. ❖ The paralysis can be partial or complete; the damage to each nerve can range from bruising to tearing. ❖ The nerves involve are the axillary nerve, musculocutaneous and supraspinatus nerves. ❖ `The affected muscles are the: ❖ The affected muscles are the: teres minor and deltoid muscles, skin of superolateral arm, muscles of the anterior compartment of the arm and the skin of lateral aspect of the forearm and the supraspinatus, infraspinatus and the supraspinatus, infraspinatus and shoulder joint.. ❖ The most common cause of Erb's palsy: Shoulder dystocia Fetal macrosomia Maternal obesity Gestational diabetes Duration of second stage of labor(over 60 minutes) Breech presentation  SYMPTOMS OF BER’S PALSY ❖ Some of the dangers of Erb’s palsy include: Full or partial paralysis in the affected arm Loss of sensory and/or motor function in the affected arm Decreased grip and arm numbness in the affected arm The affected arm may be bent towards the body or hang limb ❖ Depending on how serious the injury is, Erb’s palsy treatment options include: Medications Surgery Physical therapy Massaging the affected arm regularly  CLINICALPRESENTATION The signs of Erb's Palsy include loss of sensation in the arm and paralysis and atrophy of the deltoid, biceps, and brachialis muscles. "The position of the limb, under such conditions, is characteristic: the arm hangs by the side and is rotated medially; the forearm is extended and pronated. The arm cannot be raised from the side; all power of flexion of the elbow is lost, as is also supination of the forearm". The resulting biceps damage is the main cause of this classic physical position commonly called "waiter's tip deformation."  Klumpke’s palsy Klumpke’s palsy involves paralysis of the forearm and hand muscles, caused by damage to the lower C8 and T1 nerves. This primarily affects the wrist and fingers, and often appears as a “clawed” hand. It is typically caused by shoulder dystocia or from grapping support during falling from a height.  Shoulder dystocia occurs when an infant becomes lodged in the mother’s pelvic bone, leading to excessive pulling and stretching during delivery. Sometimes, Klumpke’s palsy will heal on its own without treatment, but for severe cases, such as partial or full paralysis, medication and surgery may be required.  SYMTOMS AND CLINICAL PRESENTATION ❑ SYMTOMS: include; ▪ Paralysis of intrinsic muscles of the hand ▪ Flexors of the wrist and finger are loss. ▪ The patient present with a Claw Hand. ▪ Involment of T1 may result in Horner’s syndrome, with ptosis, and miosis.