Nerves of the Upper Limb Flashcards
What types of nerves make up the brachial plexus?
ventral rami of the spinal nerves
What does the brachial plexus provide?
somatomotor and somatosenstory innervation to the upper extremity
What is the cervical enlargement?
ventral rami of spinal nerves C5-T1
-gives rise to brachial plexus
What muscles does the brachial plexus pass through?
the anterior and middle scalene muscles
What is the space in which the brachial plexus passes through the scalene muscles called?
the interscalene space
What is the supraclavicular region?
the region that above the clavicle
Where does the subclavian artery run?
posterior to the anterior scalene with the brachial plexus
-not with the subclavian v.
What is an interscalene block?
administration of anesthesia into the interscalene space to block the brachial plexus
What nerve can also be affected by an interscalene block?
the phrenic nerve
-affect breathing
where does the axillary artery travel?
runs in the middle of the brachial plexus
does the brachial plexus travel anterior or posterior to clavicle?
posterior
where does the axillary vein travel?
“entangled” with branches of the brachial plexus
what surrounds the brachial plexus along with the axillary a. and v. as it runs into the axilla?
axillary sheath
(concentration of fascia NOT a tube)
what is an area of cutaneous sensory innervation supplied by a single spinal nerve?
dermatome
what dermatome is supplied by C4?
supraclavicular and upper shoulder region
what dermatome is supplied by C5?
upper lateral arm and shoulder
what dermatome is supplied by C6?
posterolateral arm and lateral forearm
what dermatome is supplied by C7?
middle of forearm and hand
what dermatome is supplied by C8?
posteromedial forearm and medial hand
what dermatome is supplied by T1?
medial arm
what dermatome is supplied by T2-T4?
axillary region
why is there not a 1:1 correspondence between named cutaneous nerves and dermatomes?
bc names nerves may be comprised of more than 1 spinal nerve and thus will span more than one dermatome
an individual named muscle in limbs are supplied by how many spinal nerves?
more than one spinal nerve
what is a group of muscles that receive motor innervation from a single spinal nerve?
myotome
can myotomes overlap?
yes
what myotome is supplied by C4?
shoulder elevation
what myotome is supplied by C5?
shoulder abduction; elbow flexion
what myotome is supplied by C6?
elbow flexion; wrist extension
what myotome is supplied by C7?
elbow extension; wrist flexion
what myotome is supplied by C8?
thumb and finger extension
what myotome is supplied by T1?
intrinsic hand muscles
what myotome is supplied by T2?
intercostal muscles
what divisions do each trunk of the brachial plexus have?
anterior and posterior
the anterior divisions of the brachial plexus trunks contribute to what?
the medial and lateral cord
anterior divisions of the brachial plexus tend to?
flex
the posterior divisions of the brachial plexus trunks contribute to what
the posterior cord
posterior divisions of the brachial plexus tend to?
extend
what nerve supplies the anterior compartment of the arm?
musculocutaneous nerve
what nerve supplies the posterior compartment of the arm?
radial nerve
what nerve supplies the anterior compartment of the forearm and hand?
ulnar & radial nerves
what nerve supplies the posterior compartment of the forearm and hand?
radial nerve
what innervates the shoulder (pectoral girdle) region?
nerves that come directly from the roots, trunks, or cords of the brachial plexus
what innervates the arm (brachial) region?
nerves from the medial cord (cutaneous), the musculocutaneous n. (anterior), and the radial n. (posterior)
what innervates the forearm (antebrachial) region?
a branch from the medial cord (cutaneous), the median and ulnar nn. (anterior), and the radial n (posterior)
what supplies motor innervation to the hand?
median and ulnar nerves
what supplies sensation innervation to the hand?
median, ulnar and radial
what parts of the brachial plexus lie in the supraclavicular region?
roots (rami) and trunks
what parts of the brachial plexus lie in the infraclavicular region?
divisions, cords, and branches
what is the order of the brachial plexus segments?
roots –> trunks –> divisions –> cords –> branches
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the upper trunk of the brachial plexus is made up of which roots?
C5 and C6
the middle trunk of the brachial plexus is made up of which roots?
C7
the lower trunk of the brachial plexus is made up of which roots?
C8 and T1
which divisions make up the lateral cord of the brachial plexus?
anterior divisions of upper and middle trunks
which divisions make up the medial cord of the brachial plexus?
anterior division of the lower trunk
which divisions make up the posterior cord of the brachial plexus?
posterior divisions of upper, middle, and lower trunks
which cords make up the musculocutaneous branch of the brachial plexus?
lateral cord
which cords make up the median branch of the brachial plexus?
lateral and medial cords
which cords make up the ulnar branch of the brachial plexus?
medial cord
which cords make up the radial branch of the brachial plexus?
posterior cord
which cords make up the axillary branch of the brachial plexus?
posterior cord
what additional nerves does the lateral cord of the brachial plexus give rise to?
lateral pectoral n.
what additional nerves does the medial cord of the brachial plexus give rise to?
medial pectoral n.
medial brachial cutaneous n.
medial antebrachial cutaneous n.
what additional nerves does the posterior cord of the brachial plexus give rise to?
upper subscapular n.
lower subscapular n.
thoracodorsal n.
what additional nerves does the upper trunk of the brachial plexus give rise to?
subclavius n.
suprascapular n.
what additional nerves does the C5 root of the brachial plexus give rise to?
dorsal scapular n.
long thoracic n.
an injury to superior trunk (C5 and C6) can be called?
Erb’s palsey
what are potential causes of Erb’s palsey?
-results from excessive, forceful increase in angle b/w neck and shoulder
-most common obstetric brachial plexopathy
-can also occur in adults from a fall onto the shoulder
what is the clinical presentation of Erb’s palsey?
-arm will be adducted
-arm will be internally (medially) rotated at the elbow
-there will be pronation
-there will be extension
what are the nerve deficits & affected muscles of Erb’s palsey?
-axillary n. (weakness in deltoid and teres minor)
-suprascapular n. (weakness in supraspinatus and infraspinatus)
-musculocutaneous n. (weakness in biceps)
-radial n. (weakness in brachioradialis and supinator, and wrist extensors)
an injury to the axillary region affects which nerves?
C5-T1 (radial nerve)
what are common causes of injury to axillary region?
improper use of crutches can compress and injure the nerve in the axilla
what is the clinical presentation of an injury to the radial nerve in the axillary region?
-weakness when trying to push something away with arm
-difficulty extending the wrist
-difficulty extending the fingers and opening the hand
-“wrist drop” posture
an injury at the spinal groove of humerus affects which nerves?
C5-T1 (compression of the radial nerve)
what is the clinical presentation of an injury at the spiral groove of humerus?
-difficulty extending the wrist
-difficulty extending or straightening the fingers and opening the hand
-triceps retains strength because nerve fibers entering this muscle branch off proximal to the mid shaft of the humerus
-also causes “wrist drop” posture
what are common causes of injury at spiral groove of humerus?
-compression of the radial nerve along the midshaft of the humerus in certain postions
-humeral fracture at midshaft (spiral groove fracture)
what are common causes of injury to the axillary nerve?
-fracture to surgical neck of humerus
-anterior dislocation of glenohumeral joint
-rotator cuff repair surgery
what is the clinical presentation of an injury to the axillary nerve?
-numbness in posterior deltoid region
-difficulty abducting arm
-diminished lateral rotation of arm
-deltoid muscle wasting (prolonged injury)
an injury to the axillary nerve affects which nerves?
C5 and C6
an injury to the long thoracic nerve affects which nerves?
C5, C6, and C7
(innervation to the serratus anterior muscles)
what are common causes of an injury to the long thoracic nerve?
-penetrating wound to the axillary region
-surgical removal of axillary lymph nodes
what is the clinical presentation of an injury to the long thoracic nerve?
-cannot raise arms above 90 degrees
-“winged scapula”
