Brachial Plexus Flashcards
Where do the nerve roots involved in the brachial plexus emerge from?
- C5 to C7from above the C5-C7vertebre
- C8 from below C7
- T1 from below T1
What nerve roots are involved in the brachial plexus?
-C5,C6, C7, C8 and T1
What nerve roots make the long thoracic nerve?
-C5, C6, C7
What does the long thoracic nerve supply?
-Serratus anterior
What results from injury to the long thoracic nerve?
-Winged scapula
What nerve roots form the superior trunk?
-C5 and C6
What nerve roots form the middle trunk?
-C7
What nerve roots form the inferior trunk?
-C8 and T1
What divisions form the lateral cord?
-Anterior divisions of the superior and middle trunks
What divisions form the posterior cord?
-Posterior divisions of all three trunks
What divisions form the medial cord?
-Anterior division of inferior trunk
What cords form the musculocutaneous branch?
-Lateral cord
What nerve roots contribute to the musculocutaneous cord?
-C5, C6, C7
What does the musculocutaneous branch innvervate?
BBC
- Biceps brachii
- Brachialis
- Coracobrachialis
What sensory function does the musculocutaneous nerve have?
-Supplies the lateral skin of the forearm (branches into lateral cutaneous nerve of forearm which supplies forearm)
Where is the musculocutaneous nerve anatomically located?
-Branch of lateral cord which runs inbetween brachialis and biceps brachii
What is the most common way in which the musculocutaneous nerve is injured?
-Stab wound to axilla
What is the result of injury to the musculocutaneous nerve?
Paralysis of BBC resulting in:
- Flexion at shoulder joint weakened but can still occur due to pec major
- Flexion at elbow joint weakened but can still occur due to brachioradialis
- Supination greatly weakened but can still occur due to supinator
- Loss of sensation over lateral forearm
What cord forms the axillary nerve?
-Posterior cord
What nerve roots contribute to the axillary nerve?
-C5 and C6
What sensory function does the axillary nerve have?
-Innervates the lateral skin of the arm (regimental badge area) via superior lateral cutaneous nerve of the arm
What muscles does the axillary nerve innervate?
- Deltoid
- Teres minor
Where does the axillary nerve leave the axilla?
-Through the quadrangular space
What artery accompanies the axillary nerve out of the quadrangular space?
-Posterior circumflex artery
What action does teres minor have singly?
-external rotation of upper limb
How is damage to axillary nerve commonly tested?
-Test regimental badge area for sensation
How is the axillary nerve most commonly injured?
-Fracture of surgical neck of humerus
What results from damage to the axillary nerve?
- Paralysis of teres monor and deltoid -> patient unable to abduct limb
- Loss of sensation over regimental badge
- If long standing damage, there will be atrophy of deltoid and greater tubercle will be palpable
What cords form the radial nerve?
-Posterior
What nerve roots contribute to the radial nerve?
-C5, C6, C7, C8 and T1
What is the motor function of the radial nerve?
-Innervates all the extensor muscles of the arm and forearm and brachioradialis
What is the sensory function of the radial nerve?
- Innervates most of the skin on the posterior arm and part of posterior forearm
- Innervates dorsal lateral 3 and half digits, bar nail beds, and corresponding dorsum of the hand
- Innervates an area over thenar eminance
Describe the anatomical course of the radial nerve
-Runs posteriorly to brachial artery down the radial groove to the lateral epicondyle through the cubital fossa. On entering the forearm the radial nerve spilts into superficial and deep branches
Which branch of the radial nerve is sensory and which is motor?
- Superficial is sensory
- Deep is motor
What are the 4 possible areas of damage to the radial nerve?
- In the axilla
- In the radial groove
- Deep branch of radial nerve
- Superficial branch of radial nerve
How does the radial nerve commonly become damaged in the axilla?
-Dislocation of glenohumeral joint or fractures of proximal humerus
What are the consequences of damaging the radial nerve in the axilla?
- Posterior compartment of arm and forearm paralysed
- Patient unale to extend forearm, wrist and fingers
- Unopposed flexion occurs ar wrist causing wrist drop
- Loss of sensation to lateral and posterior arm, posterior forearm and to lateral 3 nd half digits, bar nail bed, and their associated dorsum
How is the radial nerve commonly injured in the radial groove?
-Fracture of shaft of humerus
What are the consequences of injuring the radial nerve in the radial groove?
- Triceps brachii may be weakened but not paralysed
- Deep branch of radial nerve affected-> muscles in posterior forearm paralysed-> wrist drop due to unopposed flexion, patient unable to extend fingers/wrist
- Loss of innervation to superficial branch of radial nerve means loss of sensation of lateral half of dorsum and lateral 3andhalf digits, bar the nailbeds
How does damage to the deep branch of the radial nerve usually occur?
- Fracture of radial head
- Posterior dislocation of radius at elbow joint
What are the consequences of a lesion to the deep branch of the radial nerve?
-Loss of motor function in posterior forearm except supinator and extensor carpi radialis longus (these are supplied by the radial nerve earlier than branching) -> unable to extend fingers. ECRL is a stong extensor of the wrist so wrist drop does not occur
How does damage to the superficial branch of the radial nerve commonly occur?
-Stabbing or laceration to forearm
What are the consequences of a lesion to the superficial branch of the radial nerve?
-Loss of sensory function to lateral dorsal 3andhalf digits and their associated dorsum
What cords contribute to the median nerve?
-Lateral and medial
What nerve roots contribute to the median nerve?
-C6, C7, C8 and T1
What are the motor functions of the median nerve?
- Innervates the muscles in the anterior forearm (except flexi carpi ulnaris and the medial half of flexi digitorum profundus)
- Innervates the thenar eminence (recurrent branch) and the lateral two lumbricals of the hand (palmar digital branch)
What are the sensory functions of the median nerve?
-Palmer lateral 3andhalf digits (except an area over thenar eminiance) and the nailbeds of the lateral 3andhalf digits
Describe the anatomical course of the median nerve
- Exits axilla and runs lateral to brachial artery, until half way where it crosses to become medial to brachial artery
- Passes into the anterior compartment of the forearm through the antecubital fossa
- Travels down the forearm between FDP and FDS and passes into the hand via the carpal tunnel
What is the cause of carpal tunnel syndrome?
- Compression of the median nerve within the carpal tunnel
- Can be by thickened ligaments and tendon sheaths but often the aetiology is idiopathic
What is the result if carpal tunnel syndrome is left untreated?
-Weakness and atrophy of the thenar muscles
How will a patient with carpal tunnel syndrome present?
- Numbness
- Parenthesia
- Pain along the distribution of the median nerve, usually radiating to the forearm
- Pain can wake patient from sleep
What is tinels sign?
-A test for carpal tunnel syndrome where the nerve is tapped within the carpal tunnel to elicit pain
What is phalen’s manoeuvre?
-A test for carpal tunnel syndrome where the wrist is helf in flexion for 60 seconds to elicit numbness/pain in median distribution
What are possible treatments of carpal tunnel syndrome?
- A splint to hold the wrist in dorsiflexion overnight to relieve pain
- Corticosteroids injections
- Surgical decompression in severe cases
How is the median nerve commonly damaged at the elbow?
-Supracondylar fracture of the humerus
What is the result of a lesion to the median nerve at the elbow?
- Flexors and pronators in forearm are paralysed, except FCU and medial half of FDP
- Forearm remains constantly supinated and flexion is weak
- Hand of benediction due to paralysis of thenar eminence and lateral two lumbricals
- Loss of sensation over palmar lateral 3andhalf digits and nailbeds
What is the hand of benediction?
- Results from median nerve lesion
- Upon trying to make a fist, only the 4th and 5th digits are able to fully flex
- The 1st is unable to flex due to paralysis of both FPL and FPB
- The second and third digits are unable to flex MCP and IP joints due to paralysis of later two lumbricals and FDS
What cords form the ulnar branch?
-Medial cord
What nerve roots contribute to the ulnar nerve?
-C8 and T1
What is the motor function of the ulnar nerve?
- Innervates FCU, and medial half of FDP
- Innervates hypothenar, adductor pollicis, interossei and medial two lumbricals
What is the sensory function of the ulnar nerve?
-Innervates the skin anteriorly and posteriorly of medial 1andhalf digits, and their associated palmar and dorsum areas
Describe the anatomical course of the ulnar nerve
- Runs medial to the brachial artery and passes behind medial epicondyle into anterior compartment of forearm where it pierces the two heads of FCU and branches
- At the wrist the ulnar nerve travels superior to flexor retinaculum but passes through guyons canal
How is the ulnar nerve commonly damaged at the elbow?
-Fracture to the medial epicondyle
What results from damaging the ulnar nerve at the elbow?
- FCU and medial half of FDP are paralysed
- flexion of the wrist can occur but is accompanied by abduction due to it being unopposed
- The interossei are paralysed so adduction and abduction cannot occur
- movement of the 4th and 5th digits is greatly reduced due to paralysis of medial two lumbricals
- Loss of sensation over medial 1andhalf digits and associated palmer dorsum areas
What is a simple test for ulnar nerve damage?
-Ask patient to grip paper placed in between digits (cannot do this as no adduction)
What is a classical sign of long-standing ulnar nerve damage?
- Ulnar claw
- hyperextension of MCP of 4th and 5th digits due to damage to medial lumbricals causing unopposed extension
- Flexion at IP due to paralysis of FDP
