brachial plexus Flashcards
DIAGRAM overview of brachial plexus
roots (anterior rami) form trunks, which form divisions, which form cords, which form terminal branches ie peripheral nerves there are branches coming off different parts- dorsal scapular and long thoracic nerve from roots, subclavian nerve etc they are either supraclavicular ie above clavicle or infraclavicular
DIAGRAM brachial plexus roots to trunks to divisions
plexus is C5-T1 C5 and 6 form upper trunk, C7 forms middle trunk, C8 and T1 form lower trunk each trunk divides into anterior and posterior divisions, with NO terminal branches coming off them
DIAGRAM divisions to cords
upper and middle anterior divisions form lateral cord, lower anterior forms medial cord, and posterior divisions of all 3 trunks form posterior cord most peripheral nerves comes from the cords- lateral forms musculocutaenuous, posterior forms axillary and radial, medal forms ulnar nerve, medial AND lateral form median nerve
DIAGRAM reason for names of cords
location relative to axillary artery- lateral to artery, medial to artery, and posterior to artery also functional reasons- posterior GENERALLY supplies posterior structures
motor nerves of different parts of upper limb
C3-7 ie some nerves NOT part of plexus supply muscles of shoulder girdle C5-6 shoulder joint muscles and elbow flexors eg shoulder abduction/adduction C7-8 elbow extensors C6-8 wrist+ coarse hand muscles (wrist extension/flexion and finger extension) C8-T1 small muscles of hand for fine movements (finger flexion, abdution, an d abductor pollicis brevis)
interesting point abot motor supply to upper limb
opposite movements are supplied by adjacent roots- C5-6 elbow flexion, C7-8 extension C6 pronation, C7-8 supination shoulder flexion C5, shoulder extension C6-7
dermatomes of upper limb
go round the upper limb- C3,4,5 in upper shoulder region, followed by C6, then mainly C7-8 in hand, then T1 posterior- C4,5 in upper shoulder, then C6, then mainly C7-8 in hand
dermatome vs cutaneous nerve patients
sensory supply has different pattern, due to the fibre recombination occurring in the plexus eg superior and inferior lateral cutanaeous nerves both supplied by C5-6 roots, but supplied via different pathways, thus different nerves
injuries to axillary nerve- causes and effects
passes under shoulder joint, so often damaged due to shoulder dislocations, and fractures of SURGICAL NECK of humerus supplies deltoid, so leads to deltoid atrophy branch coming off it is superior lateral cutaneous nerve- thus area of skin supplied by is loses sensation, which can be tested- in area aka regimental badge ie where soldiers put badge
injuries to radial nerve- causes and effects
runs close to shaft of humerus (in radial groove), so can be damaged by shaft fractures leads to wrist droop (extensor forearm muscles not working, and loss of sensation of dorsal hand (posterior part of hand) loss of tricep muscles arm as well loss of POWER GRIP as well, as extensor muscles needed for stability
injuries to musculocutaneous nerve- muscle pierced, causes
pierces coracobrachialis well protected by muscles so not often injured in trauma- may be damaged during surgery for breast cancer, as in area where many lymph nodes are leads to lateral forarm sensory loss, weak flexion/supination
DIAGRAM injuries to ulnar nerve- causes, effect, but good thing
often damage behind medial epicondyle ie funny bone, AND at wrist (self harm can damage area) causes claw appearance due to loss of lumbricles (ie no flexion at MC joint, and extension at IP joint), loss of adduction/abduction thumb, index and middle finger mostly spared, as ulnar nerve supplies mostly medial 1 and a half digit- sensory problems incoveiient but not as bad as median nerve damage, as again only medial 1 and half digits effected
ulnar paradox
unlike other nerves where the more proximal the injury, the worse, injury at the wrist leads to a worse injury compared to at elbow, as it innervates half of FDP= less claw deformity THE CLOSER TO PAW, THE WORSE THE CLAW
DIAGRAM supply of median nerve
gives off recurrent branch to thumb, and sensory branches to thumb, index, middle and lateral half of ring finger (cutaneous) also gives off superficial branch to palm BEFORE entering carpal tunnel
DIAGRAM carpal tunnel syndrome- importance and effects
most common nerve entrapment problem- leads to wasting of thenar eminene (adductor policis longus STILL INTACT) loss of sensation in lateral part of hand, as well as fine movement (in thumb due to thenar muscles, and digits due to lateral 2 lumbricles)
DIAGRAM damage to long thoracic nerve- vulnerability and consequence
superficial, so easily damaged serratus anterior attaches trunk ie ribs to medial edge of scapula, so holds scapula down= winging of scapula when pressing against wall
DIAGRAM damage to upper roots (ERB palsy) cause and effect, with nerves effected
can occurring during car crash and to baby during child birth (C5-6)- affects lots of nerves leads to waiters tip postion- many muscles wasted, forearm pronated (no bicep supination) and flexed= devastating to limb mobility
