GL-25 Brachial Plexus Flashcards
List the nerves of the brachial plexus that course through the arm
Musculocutaneous Nerve Medial Cutaneous Nerve of Arm Medial Cutaneous Nerve of Forearm Median Nerve Ulnar Nerve Axillary Nerve Radial Nerve
Musculocutaneous Nerve
Origin
Spinal Segments
Function (motor and/or sensory)
origin: lateral cord of brachial plexus
spinal segments: C5 to C7
function: motor-all muscles in anterior compartment of arm; sensory–lateral part of forearm
Medial Cutaneous Nerve of Arm
Origin
Spinal Segments
Function (motor and/or sensory)
Origin: Medial Cord
Spinal Segments: C8, T1
Function: sensory ONLY; skin on medial side of distal 1/3 of arm
Medial Cutaneous Nerve of Forearm
Origin
Spinal Segments
Function (motor and/or sensory)
Origin: medial Cord
Spinal Segments: C8, T1
Function: sensory ONLY; skin on medial side of forearm
Median Nerve
Origin
Spinal Segments
Function (motor and/or sensory)
origin: medial and lateral cords
spinal segments: (C5), C6 to T1
Function:
motor
(a) all muscles in the anterior compartment of the forearm except the flexor carpi ulnaris and medial half of flexor digitorum profundus
(b) 3 thenar muscles of the thumb & 2 lateral lumbrical muscles
sensory
(a) skin over the lateral palmar surface & associated fingers
(b) skin on middle of wrist
Ulnar Nerve
Origin
Spinal Segments
Functions (motor and or sensory)
Origin: medial cord
Spinal Segments: (C7), C8, T1
Functions:
motor:
(a) all intrinsic muscles of the hand except 3 thenar muscles 2 3 lateral lumbricals
(b) flexor carpi ulnaris & medial half of flexor digitorum profundus in the forearm
sensory
(a) : skin over palmar surface of medial 1 & 1/2 digits and associated palm and wrist
(b) skin over the dorsal surface of the medial one and one half digits
Axillary Nerve
Origin
Spinal Cord Segments
Function
Origin: Posterior Cord Spinal Cord Segment: C5, C6 Function: motor: deltoid, teres minor sensory: skin over upper lateral part of the arm
Radial Nerve
Origin
Spinal Cord Segments
Function
Origin: Posterior Cord
Spinal Segmentes: C5 to C8 (T1)
Function:
motor: all muscles in the posterior compartment of arm and forearm
sensory: skin on the posterior aspects of the arm and forearm, lower lateral surface of the arm, and the dorsal lateral surface of the hand
List the fiber types of the nerves present in the branches of the brachial plexus
postganglionic sympathetic, somatic afferent and efferent, sensory
What type of plexus is the brachial plexus?
somatic plexus
Describe the organization of the brachial plexus from its roots to its terminal braches
Roots, Trunks, Divisions, Cords, Branches
“Randy Travis Drinks Cold Beer”
What are the roots of the brachial plexus?
ventral rami of C5-T1
What are the trunks of the brachial plexus?
Superior (C5, C6)
Middle (C7)
Inferior (C8, T1)
What are the divisions of the brachial plexus?
Anterior (flexors)
Posterior (extensors)
What are the cords of the brachial plexus?
Lateral (C5, C6, C7)
Posterior (C5-T1)
Medial (C8-T1)
Which root(s) of the brachial plexus have branches? What are the those branches (list SC level contributions for each nerve)
Superior root is the only root to have branches
Dorsal Scapular Nerve (C5)
Long Thoracic Nerve (C5-C7)
Accessory Phrenic (C5)
“Roots Don’t Lie, Pal”
What trunk(s) of the brachial plexus have branches? What are those branches (list SC level contributions for each nerve)
Only the superior trunk has branches
Suprascapular Nerve (C5, C6) Nerve to the Subclavius Muscle (Subclavian Nerve, C5, C6)
What are the branches of the lateral cord? (list the SC level contributions for each nerve)
lateral pectoral nerve (C5 to C7)
lateral root of the median nerve
musculocutaneous nerve (terminal part is the lateral cutaneous nerve of forearm)
What are the branches of the medial cord? (list the SC level contributions for each nerve)
medial pectoral nerve (C8 to T1) medial cutaneous nerve of arm (C8, T1) medial cutaneous nerve of forearm (C8, T1) medial root of the median nerve ulnar nerve ((C7), C8, T1)
What are the branches of the posterior cord (list the SC level contributions for each nerve) -
superior subscapular nerve (C5 to C6) thoradorsal nerve (C6 to C8) inferior subscapular nerve (C5, C6) axillary nerve (C5, C6) Radial Nerve (largest terminal branch of the posterior cord, C5 to C8, sometimes T1)
STI are rad
Describe the signs and symptoms of a lower brachial plexus nerve lesion (also need to be able to explain how it happens, result, signs/symptoms)
this type of injury is an lower trunk or “klempke’s” palsy
how: angle b/w arm and chest is increased too much (usually by arm being delivered 1st in babies or grabbing tree branch in adults)
result: tears C7, C8, and T1 nerves off the spinal cord
signs/symptoms: loss of hand function, with the fingers contracted in a “claw” position
this is most likely to affect the ulnar nerve
Describe the signs and symptoms of an upper brachial plexus nerve lesion (also need to be able to explain how it happens, result, signs/symptoms)
this type of injury is known as a lower trunk or “erb’s” palsy, “waiter’s tip hand”
how: angle b/w shoulder and head is increased too much (in babies, the shoulder is delivered first; in adults, usually by MVC that forces the shoulder down and the head goes in the opposite direction)
result: C5-C7 spinal roots are injured
signs/symptoms: unable to use the shoulder to raise the arm away from the body, unable to bend the arm at the elbow, weakness in the arm
this type of injury usually damages the musculocutaneous nerve
What major muscle group does the musculocutaneous nerve supply? List the muscles in that group
muscle group: anterior compartment of the arm (flexors)
muscles: biceps brachii, coracobrachialis, brachialis
What major muscle group does the radial nerve supply? List the muscles in that group
muscle group: posterior compartment of the arm and forearm (extensors)
muscle
posterior arm: triceps brachii
posterior forearm: (see wrist and forearm learning objectives)
What major muscles does the axillary nerve supply?
deltoid
teres minor
What major muscle group does the median nerve supply?
anterior compartment of the forearm (except flexor carpi ulnaris & medial half of flexor digitorum profundus), 3 threnar muscles of thumb & 2 lateral lumbrical muscles
What major muscle group does the ulnar nerve supply?
all intrinsic muscles of the hand except the 3 threnar muscles and 2 lateral lumbricals, also supplies flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the forearm
Describe how brachial plexus injuries usually happen
they are the result of blunt trauma producing nerve avulsions and disruptions
Injuries in the cervical region affect what parts of the brachial plexus?
the roots
injuries of the 1st rib usually affect what part of the brachial plexus?
the trunks
How are the divisions and cords of the brachial plexus usually injured?
by the dislocation of the glenohumeral joint
Biceps Tendon Test
tests function of C6 spinal root
Triceps Tendon Test
tests function of C7 spinal root
Median Nerve Injury result
carpal tunnel syndrome
Radial Nerve Injury result
wrist drop
Long Thoracic Nerve Injury Result
winged scapula
How can you test the function of the spinal accessory nerve?
asking the patient to shrug their shoulders
Symptoms of a lesion to the spinal accessory nerve
patient will be unable to shrug shoulders against resistance (b/c spinal accessory innervates trapezius & w/o it you cant elevate or depress the scapula)
Symptoms of a lesion to the dorsal scapular nerve
won’t be able to elevate or retract the scapula
Symptoms of a lesion to the long thoracic nerve
injury will cause winged scapula
Symptoms of a lesion to the suprascapular nerve
supplies supra&infraspinatus (rotator cuff); injury will mess up abduction & lateral rotation of the arm
Symptoms of a lesion to the thoracodorsal nerve
unable to extend, adduct, and medially rotate the humerus (b/c it supplies the latissimus dorsi)
