Upper Limb Nerves Flashcards
What is the brachial plexus formed by?
C5, C6, C7, C8, and T1 spinal nerves.
What are the five parts, in order, of the brachial plexus?
Roots, trunks, divisions, cords, and branches.
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What are the roots of the brachial plexus?
C5, C6, C7, C8, and T1 spinal nerves.
How do the spinal nerves of the brachial plexus leave the spinal cord?
Via the intervertebral foramina of the vertebral column.
What are the brachial plexus roots formed by?
The anterior divisions of C5-T1 spinal nerves.
After formation, how do the spinal nerves of the brachial plexus enter the base of the neck?
By passing between the anterior and medial scalene muscles.
What are the trunks of the brachial plexus?
Superior, middle, and inferior.
What are the three trunks of the brachial plexus made of?
Superior - C5 and C6 roots.
Middle - C7 root continuation.
Inferior - C8 and T1 roots.
Where do the trunks of the brachial plexus go?
Move laterally, crossing the posterior triangle of the neck.
What are the divisions of the brachial plexus?
Each trunk divides into two: anterior division and posterior division.
Where do the divisions of the brachial plexus go?
Leave the posterior triangle and pass into the axilla region.
Where do divisions of the brachial plexus combine into cords?
In the axilla.
How are the cords of the brachial plexus named?
By their relative position to the axillary artery.
What are the cords of the brachial plexus?
Lateral cord, posterior cord, and medial cord.
What are the cords of the brachial plexus formed by?
Lateral cord - anterior divisions of superior and middle trunk.
Posterior cord - posterior divisions of the superior, middle, and inferior trunks.
Medial cord - anterior division fo the inferior trunk.
What are the main branches of the brachial plexus?
Musculocutaneous nerve, axillary nerve, median nerve, radial nerve, and ulnar nerve.
What can be looked for when identifying a dissected brachial plexus?
‘M’ shape formed by the musculocutaneous, median, and ulnar nerves around the brachial artery.
What are the minor branches of the brachial plexus? List them according to the part of the brachial plexus they branch off from.
Roots: dorsal scapular nerve, long thoracic.
Trunks: suprascapular nerve, subclavian nerve.
Lateral cord: lateral pectoral nerve.
Medial cord: medial pectoral nerve, medial cutaneous nerve of arm, medial cutaneous nerve of forearm.
Posterior cord: superior subscapular nerve, thoracodorsal nerve, inferior subscapular nerve.
What is Erb’s palsy?
A brachial plexus injury from excessive increase in the angle between the neck and shoulder (like in childbirth or shoulder trauma) that damages nerve roots.
What are the nerves affected in Erb’s palsy?
Those derived from solely C5 or C6 roots: musculocutaneous, axillary, suprascapular and subclavian nerve.
What muscles are paralysed in Erb’s palsy?
Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid, and teres minor.
What motor functions are affected in Erb’s palsy?
Weakened movements: abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder.
What sensory functions are affected in Erb’s palsy?
Loss of sensation down lateral side of arm, which covers the sensory innervation of the axillary and musculocutaneous nerves.
What is the waiter’s tip position in Erb’s palsy caused by?
Unapposed action of pectoralis major so the affected limb hangs limp and is medially rotated. The forearm is pronated due to loss of biceps brachii.
What is Klumpke palsy?
A brachial plexus injury due to excessive abduction of the arm (e.g. falling from tree and grabbing a branch).
What nerves are affected in Klumpke palsy?
Nerves derived from the T1 root, ulna and median nerves.
What are the muscles affected in Klumpke palsy?
Small muscles of the hand.
What sensory functions are affected in Klumpke palsy?
Loss of sensation along the medial side of the arm.
What happens in the hand joints in Klumpke palsy?
The metacarpophalangeal are hyperextended, and the interphalangeal joins are flexed. This makes the hand clawed.
What are the spinal roots of the axillary nerve?
C5 and C6.
What are the sensory functions of the axillary nerve?
Gives rise to superior lateral cutaneous nerve of arm, which innervates the skin over the lower deltoid (regimental badge area).
What are the motor functions of the axillary nerve?
Innervates the teres minor and deltoid muscle, abductors of the arm at the shoulder.
Where does the axillary nerve run after formation?
It lies posteriorly to the axillary artery and anteriorly to the subscapularis muscle.
What is the anatomical course of the axillary artery?
It is formed within the axilla region as a direct continuation of the posterior cord of the brachial plexus. It lies posteriorly to the axillary artery and anteriorly to the subscapularis muscle and descends to the inferior border of the subscapularis muscle, and exits the axilla posteriorly via quadrangular space accompanies by the posterior circumflex humeral artery. It terminates into two branches in the posterior scapula region - posterior terminal branch and anterior terminal branch.
What do the two terminal branches of the axillary nerve (posterior and anterior) supply?
Posterior terminal branch - motor innervation to the teres minor muscle, sensory innervation to the skin over the inferior part of the deltoid.
Anterior terminal branch - motor innervation to the deltoid muscle.
What is the quadrangular space?
A gap in the muscles of the posterior scapular region. A pathway for neurovascular structures to move from the axilla to the posterior shoulder and arm.
What are the boundaries of the quadrangular space?
Superior - subscapularis and teres minor.
Inferior - teres major.
Laterally - surgical head of humerus.
Medially - long head of triceps brachii.
What can cause axillary nerve injury?
Trauma to the shoulder or proximal humerus, like a fracture of the humerus surgical neck.
How would motor functions be affected by axillary nerve damage?
Paralysis of the deltoid and teres minor muscles. So the patient is unable to abduct the affected limb.
How would sensory functions be affected by axillary nerve damage?
The upper lateral cutaneous nerve of the arm will be non functional, so there will be a loss of sensation over the regimental badge area.
What is a clinical characteristic sign of axillary nerve damage?
Paralysed deltoid muscle can rapidly atrophy, so the greater tuberosity can be palpated.
What are the spinal roots of the musculocutaneous nerve?
C5, C6, and C7.
What are the motor functions of the musculocutaneous nerve?
Innervates the muscles in the anterior compartment of the arm, the coracobrachialis, biceps brachii, and the brachialis.
Innervates the BBC.
What are the sensory functions of the musculocutaneous nerve?
Gives rise to the lateral cutaneous nerve of the forearm, which innervates the skin on the lateral surface of the forearm.
What is the anatomical course of the musculocutaneous nerve?
Arises from the lateral cord of the brachial plexus, then leave the axilla, piercing the coracobraachialis near its point of insertion on the humerus. It then continues down the arm, anterior to the brachialis muscle but deep to the biceps brachii, innervating both of them. It emerges lateral to the biceps tendon, and continues into the forearm as the lateral cutaneous nerve.
What can cause musculocutaneous nerve injury?
Uncommon as it is well protected within the axilla. Normally from stab wound to the axilla.
How would motor functions be affected by musculocutaneous nerve damage?
Biceps brachii, brachialis, and coracobrachialis muscles are paralysed. Flexion at the shoulder is weakened, but still able because of the pectoralis major. Flexion at the elbow is weakened, but still able due to brachioradialis muscle. Supination of the limb is very weak but still able due to supinator muscle action.
How would sensory functions be affected by musculocutaneous nerve damage?
Loss of sensation over the lateral side of the forearm.
What are the nerve roots of the median nerve?
C5, C6, C7, C8, and T1.
What are the motor functions of the median nerve?
Innervates the flexor muscles in the anterior compartment of the forearm: pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis (except the flexor carpi ulnaris and part of the flexor digitorum profundus, which are innervated by the ulnar nerve). Also teh flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus (anterior interosseous nerve).
Also innervates the thenar muscles (recurrent branch), and lateral two lumbricals in the hand (palmar digital branch).
What are the sensory functions of the median nerve?
Gives rise to the palmar cutaneous branch, innervates the lateral part of the palm, and the digital cutaneous branch, innervates the lateral three and a half fingers on the palmar surface of the hand.
What is the anatomical course of the median nerve?
Derived from the medial and lateral cords of the brachial plexus. Descends down the arm, lateral to the brachial artery at first, but halfway down the arm, it crosses over the brachial artery and situated itself medially to the brachial artery. The nerve enters the anterior compartment of the forearm via the cubital fossa. It gives rise to the anterior interosseous nerve and palmar cutaneous nerve in the forearm. It then enters the hand via the carpal tunnel and terminates by dividing into the recurrent branch and palmar digital branch.
What do the anterior interosseous nerve and palmar cutaneous nerves supply (from the median nerve)?
Anterior interosseous nerve - deep muscles in the anterior forearm.
Palmar cutaneous nerve - innervates the skin of the lateral palm.
What do the terminal branches of the median nerve supply (recurrent branch and palmar digital branch)?
Recurrent branch - innervates the thenar muscles.
Palmar digital branch - innervates palmar surface and fingertips of the lateral three and half digits. Innervates the lateral two lumbrical muscles.
What causes carpal tunnel syndrome?
Compression of the median nerve within the carpal tunnel. Compression due to thickened ligaments and tendon sheaths.
What can carpal tunnel cause?
Weakness and atrophy of the thenar muscles.
What are the symptoms of carpal tunnel syndrome?
Numbness, tingling and pain in the distribution of the carpal tunnel and radiating to the forearm.
How can carpal tunnel syndrome by tested?
Tinels sign - tapping the nerve in the carpal tunnel to elicit pain in the median nerve distribution.
Phalens sign - hold the wrist in flexion for 60 seconds to elicit numbness/ pain in median nerve distribution.
How is carpal tunnel syndrome treated?
Using a splint that hold the wrist in dorsiflexion overnight. Corticosteroids can also be injected into the carpal tunnel or in severe cases, surgical decompression of the carpal tunnel.
How can the median nerve be damaged at the elbow?
After supracondylar fracture of the humerus.
What motor functions are affected with median nerve damage at the elbow?
Flexors and pronators in the forearm are paralysed, except the flexor carpi ulnaris and medial half of the flexor digitorum profundus. So the forearm is constantly supinated and flexion is weak. Flexion of the thumb is prevented due to paralysis of the longus and brevis muscle. Flexion at the metacarpophalangeal joints is prevented and extension of the interphalangeal joints are also prevented of the index and middle finders.
What sensory functions are affected with median nerve damage at the elbow?
Lack of sensation over the areas that the median nerve innervates.
What is the characteristic sign of damage to the median nerve at the elbow?
Thenar eminence is wasted, due to atrophy of the thenar muscles, unable to make a fist (only with little and ring fingers). Hand of benediction.
How can the median nerve be damaged at the wrist?
Laceration just proximal to the flexor retinaculum.
What motor functions are affected with median nerve damage at the wrist?
Thenar muscles and lateral two lumbricals are paralysed. Opposition of thumb and flexion of index and middle fingers are affected.
What sensory functions are affected with median nerve damage at the wrist?
Lack of sensation over the areas that the median nerve innervates.
What are the characteristic signs of damage to the median nerve at the wrist?
Thenar eminence is wasted, due to atrophy of the thenar muscles, unable to make a fist (only with little and ring fingers). Hand of benediction.
What are the nerve roots of the radial nerve?
C5, C6, C7, C8, and T1.
What are the sensory functions of the radial nerve?
Innervates most of the skin of the posterior side of forearm, and the dorsal surface of the lateral side of the palm, and lateral three and a half digits.
What are the motor functions of the radial nerve?
Innervates the triceps brachii (extension at elbow), and the majority of the extensor muscles in the forearm (extension of wrist and fingers and supination of forearm).
What is the anatomical course of the radial nerve?
Continuation of the posterior cord of the brachial plexus. Exits axilla posteriorly to the brachial artery and supplies the long and medial heads of the triceps brachii. Descends down the arm along the radial groove of the humerus. It moves inferiorly and wraps around the humerus in the lateral direction and gives a branch to the lateral head of the triceps brachii. Enters the forearm moving anteriorly over the lateral epicondyle of the humerus through the cubital fossa. Terminates in the forearm by splitting into two branches: deep and superficial.
What are the functions of the terminal branches of the radial nerve (deep and superficial branches)?
Deep branch - motor branch, innervates the muscles in the posterior compartment of the forearm.
Superficial branch - sensory branch, contributes to the cutaneous innervation of the hand and fingers.
What are the four branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb?
Lower lateral cutaneous nerve of arm - innervates lateral aspect of upper arm, below deltoid muscle.
Posterior cutaneous nerve of arm - innervates the posterior surface of the upper arm.
Posterior cutaneous nerve of forearm - innervates a strip of skin down the middle of the posterior forearm.
Superficial branch of the radial nerve - innervates the dorsal surface of the lateral three and a half digits, and their associated palm area.
How does injury to the radial nerve in the axilla occur?
Dislocation of the humerus at the glenohumeral joint, fractures of the proximal humerus or excessive pressure on the axilla.
What are the motor functions affected with damage to the radial nerve in the axilla?
Triceps brachii and muscles in the posterior compartment are paralysed. Unable to extend forearm, wrist and fingers. Unopposed flexion of the wrist - wrist drop.
What are the sensory functions affected with damage to the radial nerve in the axilla?
All four cutaneous branches affected so loss of sensation over the lateral and posterior upper arm, posterior forearm, and dorsal surface of the lateral three and a half digits.
How does injury to the radial nerve in the radial groove occur?
Fracture of the shaft of the humerus.
What are the motor functions affected with damage to the radial nerve in the radial groove?
Triceps brachii weakened but no paralysed. Deep branch of radial nerve affected so posterior forearm muscles are paralysed. Unable to extend the wrist and fingers. Unopposed flexion of wrist - wrist drop.
What are the sensory functions affected with damage to the radial nerve in the radial groove?
Superficial branch of the radial nerve is damaged, so sensory loss on the dorsal surface of the lateral three and a half digits, and their associated palm area.
How does injury to the deep branch of the radial nerve occur?
Fractures of the radial head, or a posterior dislocation of the radius at the elbow joint.
What are the motor functions affected with damage to the deep branch of the radial nerve?
Muscles in the posterior compartment of the forearm are affected, except the supinator and extensor carpi radialis longus. No wrist drop.
What are the sensory functions affected with damage to the deep branch of the radial nerve?
None, only a motor nerve is affected.
How does injury to the superficial branch of the radial nerve occur?
Stabbing or laceration of the forearm.
What are the motor functions affected with damage to the superficial branch of the radial nerve?
None, only a sensory nerve is affected.
What are the sensory functions affected with damage to the superficial branch of the radial nerve?
Sensory loss affecting the dorsal surface of the lateral three and a half digits and their associated palm area.
What are the spinal roots of the ulnar nerve?
C8-T1.
What are the motor functions of the ulnar nerve?
Innervates the muscles of the hand (except thenar muscles and two lateral lumbricals), flexor carpi ulnaris, and medial half of flexor digitorum profundus.
What are the sensory functions of the ulnar nerve?
Innervates the anterior and posterior surfaces of the medial one and a half fingers, and their associated palm area.
What is the anatomical course of the ulnar nerve?
Continuation of the medial cord of the brachial plexus. It descends down the medial side of the upper arm, at the elbow it passes posterior to the medial epicondyle and enters the forearm. It pierces the two heads of the flexor carpi ulnaris and travels alongside the ulna artery.. It branches into three: muscular bracnh, palmar cutaneous branch, and dorsal cutaneous branch in the forearm. At the wrist, it travels superficially to the flexor retinaculum and enters the hand via the ulnar canal. Terminates here by giving rise to superficial and deep branches.
What do the three forearm branches of the ulnar nerve (muscular, palmar cutaneous and dorsal cutaneous) innervate?
Muscular branch- innervates some muscles in the anterior compartment of the forearm.
Palmar cutaneous branch - innervates skin of the medial half of the palm.
Dorsal cutaneous branch - innervates the skin of the medial one and a half fingers and the associated palm area.
How does damage to the ulnar nerve at the elbow occur?
Fracture of the medial epicondyle.
What are the motor functions affected by damage to the ulnar nerve at the elbow?
Flexor carpi ulnaris and medial half of flexor digitorum profundus paralysed. Flexion at the wrist can occur but only with abduction. Interossei are paralysed so abduction and adduction of the fingers can’t happen. Little and ring finger movement is greatly reduced as the medial two lumbricals are paralysed.
What are the sensory functions affected by damage to the ulnar nerve at the elbow?
All sensory branches affected, so sensory loss over all areas the ulnar nerve innervates.
What is the characteristic sign of damage to the ulnar nerve at the elbow?
Can’t grip paper between fingers.
How does damage to the ulnar nerve at the wrist occur?
Lacerations to the wrist.
What are the motor functions affected by damage to the ulnar nerve at the wrist?
Interossei paralysed so abduction and adduction of fingers can’t occur. Little and ring finger movement is reduced greatly due to paralysis of the medial two lumbricals. Muscles in forearm are unaffected.
What are the sensory functions affected by damage to the ulnar nerve at the wrist?
Palmar branch and superficial branch are severed, but dorsal branch is unaffected. So sensory loss over palmar side of medial one and half fingers.
What is the characteristic sign of damage to the ulnar nerve at the wrist?
Can’t grip paper between fingers. Long-term, ulnar claw develops - hyperextension of metacarpophalangeal joints of little and ring fingers form paralysed medial two lumbrical and unopposed action of extensor muscles, also flexion at the interphalangeal joints from flexor digitorum profundus paralysis.
What are the nerves involved in ulnar claw and hand of benediction?
UC - ulnar nerve at wrist.
HOB - median nerve at the elbow or wrist.
What are the typical presentation of ulnar claw and hand of benediction?
UC - long standing cases of nerve damage.
HOB - when patient attempts to make a fist.
What are the digits affected in ulnar claw and hand of benediction?
UC - little and ring fingers.
HOB - middle and index fingers.
What muscles are paralysed in ulnar claw and hand of benediction?
UC - medial two lumbricals.
HOB - lateral half of flexor digitorum profundus and lateral two lumbricals.
What are the movements involved in ulnar claw and hand of benediction?
UC - unopposed extension at metacarpophalangeal joints, unopposed flexion at the interphalangeal joints.
HOB - inability to perform flexion at the metacarpophalangeal and interphalangeal joints of the middle and index fingers.
