Upper Limb Nerves , Dermatomes & Myotomes Flashcards
Branches that exit the brachial plexus “superior” to the clavicle and largely located in the cervical region are called:
Supraclavicular Branches
Branches exit plexus inferior to clavicle and are primarily located in the axilla/armpit are called:
Infraclavicular Branches (terminal Branches)
what important branches make up the supraclavicular branches
Long Thoracic Nerve
Suprascapular Nerve
Dorsal Scapular Nerve
what important branches make up the infraclavicular branches (hint: MARMU)
MARMU
Musculocutaneous (C5,6,7)
Axillary (C5/6)
Radial (C5 – T1)
Median (C5 – T1)
Ulnar (C8/T1)
origin of musculocutaneous nerve
terminal branch of lateral cord
functions of musculocutaneous nerve
motor function to anterior arm:
- coracobrachialis
- biceps
- brachialis
Sensory to
- the skin of the anterolateral forearm
Pathway of musculocutaneous nerve
- the terminal branch of the lateral cord within the axilla
- travels through the coracobrachialis muscle belly
- innervates muscles of the anterior compartment of the arm
- continues after passing the cubital fossa as the lateral cutaneous N. of the forearm
which is the most likely site of injury to the musculocutaneous nerve?
- when it travels through the coracobrachialis muscle belly
origin of axillary nerve
the terminal branch of the posterior cord
the function of axillary nerve
motor to lateral shoulder:
- deltoid
- teres minor
sensory to:
- skin of lateral shoulder
Pathway of axillary nerve
- heads posteriorly in axilla
- travels through the quadrangular axillary space
- wraps around the posterior aspect of the humeral neck
- relationship with the surgical neck of humorous
- innervates deltoid and teres minor
what is the most likely site of injury for the axillary nerve?
in the pathway where it has a relationship with the surgical neck of the humerus
“military patch syndrome” is an injury to which nerve
axillary
what occurs when a patient has “military patch syndrome”
weakness is abduction
weakness in lateral (external) rotation
numbness and tingling in the lateral shoulder
origin of the radial branch
the terminal branch of the posterior cord
the function of the radial branch
motor to:
- extensor muscles of the posterior arm
- extensor muscles of the posterior forearm
- brachoradialis
- supinator muscle
sensory to:
- skin of posterior arm, forearm and hand
- dorsal surface of digits 1,2,3 and lateral 1/2 of digit 4
(typically written as lateral 3.5 digits, dorsal surface)
radial nerve pathway
- head posteriorly in axilla
- travels posteriorly, inferior to the quadrangular axillary space
- wraps around the posterior aspect of the humeral shaft
- relationship with the radial groove of the humerus
- innervates extensors of arm and forearm and supinator
what is the most likely site of injury for the radial nerve?
in the pathway at its relationship with the radial groove of the humerus
Radial nerve: sensory branches in the posterior arm
posterior cutaneous nerve of forearm
lower lateral cutaneous nerve of arm
The terminal deep branch of the radial nerve is ______. It innervates
motor
- innervates the muscles in the posterior compartment of the forearm
The terminal superficial branch of the radial nerve is ______. It innervates
sensory
- it contributes to the cutaneous innervation of the dorsal hand and fingers
Wrist drop is an indication of injury to which nerve
radial nerve
injury of the radial nerve results in the loss of what action?
Loss of extension of forearm, elbow, wrist and fingers
Weakness in supination (but not loss of because biceps also does supination)
origin of the median nerve
the terminal branch of lateral and medial cords
function of median nerve
motor to muscles of the anterior forearm and hand:
- flexors of the wrist
- pronators of the forearm
- flexors of digits 1,2,3
- lumbrical 1 and 2
- thenar muscles
sensory to:
- palmar surface of digits 1,2,3 and lateral 1/2 of digit 4 (typically written as lateral 3.5 digits, palmar surface)
pathway of the median nerve
- heads inferiorly from the axilla, travelling down an anteromedial arm (within layers of muscle)
- crosses anterior elbow within the cubital fossa
- travels down the anterior forearm
- enters hand via carpal tunnel
what are the TWO likely sites of injury for the median nerve?
when it crosses the anterior elbow within the cubital and when it enters the hand via the carpal tunnel
carpal tunnel syndrome is an injury of which nerve
the median nerve
the compression of the median nerve as it passes through the carpal tunnel. Name 4 possible causes of disease.
Carpal tunnel syndrome
- typing, mechanics, pregnancy and obesity
where will carpal tunnel impact first? What does the patient often complain of?
the median nerve in the hand (motor and sensory)
- The patient often complains of numbness and tingling in the first 3.5 digits and weakness of thumb movement
as the condition of carpal tunnel progresses, where can sensory changes radiate into?
the forearm and even the axilla
how do you relieve symptoms of carpal tunnel?
To relieve symptoms, partial or complete surgical division of the flexor retinaculum may be necessary – this is known as ‘carpal tunnel release
ape hand deformity is an indication of injury to which nerve?
median nerve
- Smaller muscles will show atrophy quicker!!!
Such as thenar muscles that support the thumb
The thumb is pulled closer to the hand because abduction is function is lost
if injury to the median nerve occurs at the elbow, what will occur?
Loss of flexion of the wrist
Loss of flexion of fingers
Loss of thumb movement
loss of Pronation
Sensation in the hand
origin of ulnar nerve
terminal branch of medial cord
function of ulnar nerve
Motor to medial forearm and hand:
- Medial ½ of flexor digitorum profundus
Hand intrinsics
- Lumbricals 3&4
- Hypothenar group
- Palmer and Dorsal Interossei
Sensory to:
- palmer and Dorsal surface of medial ½ of digit 4
- And all if digit 5 (typically written as medial 1.5 digits)
pathway of ulnar nerve
heads inferiorly from the axilla, travelling down the anteromedial arm (protected by muscle)
- passes posterior to medial epicondyle
- travels down the medial forearm
- enters hand external to carpal tunnel
what is the most likely site of injury to the ulnar nerve?
when it passes posterior to the medial epicondyle
injury to ulnar nerve results in:
ulnar claw hand
- Significant Loss of hand functions 2,3,4,5
Small muscles are higher risk for developing atrophy
Cutaneous Supply from Brachial Plexus: Median
Palmer surface of lateral 3.5 digits
Cutaneous Supply from Brachial Plexus: Ulnar
Palmer and dorsal surface of medial 1.5 digits
Cutaneous Supply from Brachial Plexus: Radial
Dorsal surface of lateral 3.5 digits
There are ___ pairs of spinal nerves exiting off spinal cord
31
Nerves are _____ matter pathways that provide a route for motor and sensory signals to travel between ___ and ____
WHITE
PNS and CNS
_________ carries sensory/afferent information INTO the CNS so it can ascend in the cord to reach the cortex
Posterior/Dorsal root
___________ root carries motor/efferent information OUT of CNS that has descended from the cortex to the cord
Ventral/Anterior
Ventral and dorsal roots come together to form a __________ in the intervertebral foramen
spinal nerve
is a specific area on the skin innervated by a specific spinal root
Dermatome
is a specific group of muscles innervated by a particular spinal root.
Myotome
Testing both dermatome and myotomes can provide important clinical feedback about the function of
spinal nerves
Dermatome: T1
medial aspect of the upper arm
Dermatome: C8
C8 little finger
Dermatome: C7
C7 middle finger
Dermatome: C4
collarbone area
Dermatome: C5
middle part of anterior arm
Dermatome: C6
C6 lateral aspect of the forearm and the thumb
Myotome: C5
deltoid
abduction of the arm at should
Myotome: C6
bicep
flexion of the arm at the elbow
Myotome: C7
tricep
extension of the arm at the elbow
Myotome: C8
small muscles of the hand
finger flexion
Myotome: T1
small muscles of the hand
finger abduction
Clinical test: __
Dermatome = sensation of skin of anterior/lateral arm (skin over deltoid)
Myotome = muscle strength of deltoid (arm abduction)
C5
Clinical Test: ___
Dermatome = sensation of anterior skin of thumb
Myotome = muscle strength of biceps (elbow flexion)
C6
Clinical Test: ___
Dermatome = sensation of anterior skin of digits 2 and 3
Myotome = muscle strength of triceps (elbow extension)
Clinical Test: C7
Clinical Test: ____
Dermatome = sensation of skin of digits 4 and 5
Myotome = muscle strength of finger flexors
Clinical Test: C8
Clinical Test: ____
Dermatome = sensation of skin of antero/medial elbow
Myotome = muscle strength of finger abductors
Clinical Test: T1
stimulus to receptors to ________ neuron, to the spinal cord to _______ neuron to effector to response
sensory neuron to motor neuron
deep tendon reflexes for C7
head of the hammer at the posterior elbow
deep tendon reflexes for C5
head of hammer at anterior the elbow
deep tendon reflexes for C6
the butt of the hammer at the radial wrist
