May23 M3-Brachial Plexus and Axilla Flashcards
armpit 3 borders (what muscles form the axilla)
- anterior: pectoralis major m.
- posterior: latissimus dorsi m. and subscapularis m.
- medial: serratus anterior m. (+ ribs)
3 pathways in upper limb
- axilla (neck to upper extremities)
- cubital fossa (arm to forearm)
- carpal tunnel (forearm to hand)
problems involving invasion of the axilla pathway (2 examples)
- tumor of lung (like pancoast tumor)
- thoracic outlet syndrome (compression of structures passing between rib1 and clavicle)
where the neurovascular bundle crosses the axilla
medially in axilla (medial border)
big arteries (is the same continuous one) to the upper extremity are what
- brachiocephalic trunk (out of arch of aorta)
- splits in carotid and subclavian a. (subclavian to the UL)
- subclavian a. becomes axillary a. after crosses rib 1
- axillary a. becomes brachial a. after it passes teres major
2 branches of the brachial a. we have to know
- humeral circumflex a. (goes around the neck of humerus)
2. deep brachial a. (goes deep to posterior arm)
axillary pulse taken how
put finger in axilla and push towards the arm
brachial pulse is taken how
in arm region, posterior to the biceps brachii m.
how do we keep the blood supply to our arm all the time (even though the subclavian, axillary, brachial a. can get compressed when we lift our arm)
anastomoses present (small routes joining subclavian and axillary to brachial a., other than the main artery)
- useful in case of ligature or compression*
- concept applies to upper and lower limbs a lot*
veins to know in armpit region and where they run
- subclavian vein -> axillary vein (after rib 1) -> basilic vein (after teres major) runs deep, on side of brachial a.
- cephalic vein runs laterally, superficially
- brachial veins (are small, deep veins) run on side of brachial a. and on side of humeral circumflex a.
lymphatics in the armpit region clinical relevance
lymph nodes surrounding the basilic-axillary vein
-may see nodule there if metastatic breast tumor
plexus definition
mingling of nerves that share info and then separate and go off
brachial plexus levels of spinal cord involved + innervates what part of the body
C5,6,7,8 + T1
(C5-T1)
-innervates upper extremities
diff stages of a plexus where spinal nerves share content
(initially, each level gives an anterior ramus)
- ramus called roots
- trunks (from some roots fusing or continuation of root)
- divisions (from trunks dividing or coninuation of trunk)
- cords (from divisions fusing or continuing)
- terminal branches (nerves)
mnemonic to remember parts of a plexus
really thirsty? drink cold beer.
Roots, trunks, divisions, cords, terminal branches (nerves. terminal branches = nerves)
how many cords and how many terminal branches in the brachial plexus
- 3 cords
- 5 terminal branches (3 come from 2 cords, last 2 come from the last cord)
where do terminal branches branch off the plexus
around axillary artery
3 cords surrounding the axillary artery and their spinal levels (names mean position relatively to the axillary a.)
- lateral cord (C5,C6,C7) (anterior arm and forearm)
- medial cord (C8, T1) (anterior arm and forearm)
- posterior cord (C5 to T1) (posterior arm and forearm)
terminal branch that is the continuation of the lateral cord and spinal levels in it
musculo-cutaneous nerve (C5,C6,C7)
terminal branch that is the continuation of the medial cord + spinal levels in it
ulnar nerve (C8, T1)
terminal branch coming off both the lateral and medial cords + levels)
median nerve (C5 to T1). both medial and lateral cord give a branch going on top of axillary artery and these 2 fuse to form the median n.
what do the spinal levels in a nerve tell us about it in the brachial plexus
- more proximal spinal levels = more proximal innervation (arm only)
- more distal = distal inn only (forearm, hand)
- all spinal levels = inn in all the upper extremity
name of the concept of how a nerve’s spinal levels content tells us where the nerve goes
gradient of the brachial plexus
clinical significance of the gradient of the brachial plexus
- general weakness in arm muscles, around shoulder = proximal injury (C5-C7)
- general weakness in forearm, hand, distally = distal lesion (C8-T1)
what region and compartment does the musculocutaneous n. innervate
anterior compartment of the arm (remember lat cord is to anterior upper extremity)
what region and compartment does the median nerve inn.
anterior compartment of the forearm and hand (remember anterior bc comes from branches of lat and medial cord which are both to anterior upper extremity)
what region does the ulnar n. inn.
forearm and hand
myotome def
group of muscles* innervated by a specific spinal level* and that serve for a specific movement*
why myotomes easy to remember
gradient of the brachial plexus so upper movements = know it’s more proximal levels for example
levels for abduction of arm, flexion, flexion of digits, abduction of digits
ABDuction of arm = C5
flexion = C6
flexion of digits = C8
ABDuction of fingers = T1
Erb Duschenne palsy general mechanism and some specific situations where can happen + affects what side
affects right side
lateral hyperextension of the neck
-infant delivery and pull head
-fall on neck
sign of Erb Duschenne palsy
Waiter’s tip position (as in arm myotomes). limb hangs by the side, shoulder lower. but muscles in distal upper extremity are very contracted (wrist contracting to back)
Dejerine-Klumpke palsy general mechanism and some specific situations where can happen + affects what side
affects left side
after hyperabduction of the arm (stretch of axilla)
-delivery of infant and pull arm
-hyperabduction while lifting something in the air
sign of Dejerine-Klumpke palsy
claw hand (weakness of intrinsic muscles of the hand), unable to close hand. + loss of sensation
Erb-Duschenne palsy vs Dejerine-Klumpke palsy
- Erb-Duschenne is upper brachial plexus injury
- Dejerine-Klumpke is lower brachial plexus injury
posterior cord of the brachial plexus (post to axillary a.) levels + innervates what
- C5 to T1
- posterior compartment of arm and forearm
terminal branches from posterior cord and levels and regions
- radial nerve (stays in the middle): C5 to T1 (inn. everything, goes all the way down)
- axillary n. goes laterally. C5,C6. stays proximal
axillary nerve innervates what region, muscle specifically
deltoid m.
radial n. inn what region
posterior compartment of arm and forearm
where to locate axillary n.
near deltoid m. if reflect deltoid m. and supraspinatus m.
2 nerves coming off the brachial plexus early, their spinal levels and the specific muscles they’re supplying
- long thoracic n. (on top of serratus anterior, postero-laterally). C5,6,7. to serratus anterior
- thoraco-dorsal n. (along ribs, to the back) C6,7,8. to latissimus dorsi m.
where long thoracic n. and thoraco-dorsal n. originate from
- long thoracic n. = from roots of brachial plexus
- thoraco-dorsal n. = from posterior cord
how to test if long thoracic n. is not damaged after a thoracentesis
ask patient to do push up on wall (test serratus anterior function): will check for wing scapula (scapula not following the ribs)
function of the serratus anterior m.
keep the scapula close to the ribs and allow protraction of the arm
what’s a wing scapula
during protraction of the arms (a push up on wall), one scapula still visible in the back bc it didn’t follow the ribs
mnemonic for serratus anterior fct and spinal levels
wing scapula (couldn’t do protraction) = fly to heaven = C5,6,7
thoraco-dorsal n. allows what movements
- ADDuction of the arm
- extension of the arm
- functions of the latissimus dorsi m.*
spaces that nerves of brachial plexus use to get to their muscles in ant and post compartments
quadrangular space and triangular interval
quadrangular space borders
- medial = long head of triceps
- lateral = humerus
- superior = subscapularis
- inferior = teres major
- this is above teres major (between subscapularis and teres major*
triangular interval borders
- superior = teres major
- lateral = humerus
- medial = long head of triceps
- this is under teres major*
structures travelling together in the quadrangular space
axillary n. and posterior humeral circumflex a. (makes sense bc quadrangular space more proximal than triangular interval and axillary n. stays proximal)
structures travelling together in the triangular space
radial n. and deep brachial a.
axillary nerve related to what structure (travels where)
neck of the humerus
radial n. related to what structure (travels where)
shaft of the humerus posteriorly
ulnar n. related to what structure (travels where)
medial epicondyle of the elbow
pathology involving radial n in the upper arm
fracture of spiral groove of the humerus
pathology involving radial n in the forearm
Wallenberg’s syndrome
pathology involving median n. in the elbow
pronator teres syndrome (compression)
pathology involving median n. in the wrist
carpal tunnel syndrome
pathology involving ulnar n. in the elbow
cubital tunnel syndrome
pathology involving ulnar n. in the elbow
Guyon’s canal syndrome
clinical case: after a night sleeping on a chair with an arm over the back of the seat, chair pressing in the axilla*: 2 structures that can be compressed FROM BELOW like that and one that is problematic
- axillary artery (not a problem) bc of anastomoses
- ulnar n. bc is medial. is first thing to be compressed from below
clinical case: after a night sleeping on a chair with an arm over the back of the seat, chair pressing in the axilla*: consequence of ulnar n. compression
weakness in the hand mainly bc C8-T1 spinal levels so distal weakness
