12 - Nerve palsies in limbs Flashcards
define dermatome?
sensory area of skin supplied by a single spinal nerve
what results in axial lines?
embryological development of limb buds growing out from body wall
is there overlap between dermatomes?
adjacent dermatomes = yes, adjacent pre/post- axial dermatomes = no
why are lower limb dermatomes distorted?
rotation and extension, and borrowing of the skin from trunk
rhyme for remembering S1-S4?
stand on S1, sleep on S2, sit on S3 and shit on S4
define Hilton’s Law?
The nerves crossing a joint supply the muscles acting on it and the joint itself
which 3 nerves supply the hip joint?
obturator nerve (predominately), femoral nerve, lateral femoral cutaneous nerve
define myotome?
group of muscles supplied by one segment of spinal cord
what is the brachial plexus?
large network of nerves supplying the upper limb, extending from the cervical spine to the axilla
name 5 divisions of the brachial plexus?
roots, trunks, divisions, cords, branches
where would damage to C5, 6 affect?
deltoid and shoulder muscles, brachialis and biceps
what palsy causes porter’s tip position?
Erb’s palsy
describe the actions of the shoulder, elbow, forearm and wrist in porter’s tip?
shoulder adduction, elbow extension, forearm pronation, wrist flexion
what does klumpke’s paralysis look like?
clawed hand
when is the axillary nerve at risk of damage?
surgical neck of humerus
what motor deficit is associated with axillary n damage?
loss of shoulder (deltoid) abduction
what sensory deficit is associated with axillary n damage?
badge area
what are the 5 nerve roots of the radial n?
C5, 6, 7, 8, T1
which artery is the radial n closely associated?
profunda brachii artery
between which 2 muscles does the radial nerve enter the forearm?
brachioradialis and brachialis
which nerves are at risk in saturday night palsy?
axillary and radial nerves
when is the radial n at risk?
spiral groove of humerus and lateral intermuscular septum
what motor deficit is associated with radial n damage?
wrist drop
what sensory deficit is associated with radial n damage?
1st web space dorsally
3 nerve roots of the median nerve?
C7, 8, T1
which artery is the median n closely associated?
brachial a
where does the median n enter the forearm?
by passing between the 2 heads of the pronator teres
what is at risk with damage to the median n?
volar aspect of the wrist (and cubital fossa)
name 2 complications associated with damage to the median n?
carpal tunnel syndrome, wrist lacerations
what motor deficit is associated with median n damage?
monkey hand (thenar wasting), pointing finger
what sensory deficit is associated with median n damage?
volar aspect thumb
3 nerve roots of the ulnar nerve?
C7, 8, T1
which arteries is the ulnar n closely associated?
superior collateral a and ulnar a
where does the ulnar n enter the forearm?
passing between the 2 heads of the flexor carpi ulnaris
where is at risk with damage to the ulnar n?
behind the medial epicondyle of humerus, wrist and canal of guyon
what motor deficit is associated with ulnar n damage?
claw hand, hypothenar and 1st dorsal interosseous wasting
what sensory deficit is associated with ulnar n damage?
little finger
where is the lumbar plexus located?
lies on surface of quadratus lumborum and within body of psoas muscle
where do most major nerves of the hip exit the pelvis?
the sciatic foramen
which nerves of the hip do not exit the pelvis via the sciatic foramen?
genitofemoral & ilioinguinal, femoral, lateral femoral cutaneous and obturator nerves
3 nerve roots of the femoral n?
L2-4
what is the largest branch of the lumbar plexus?
femoral nerve
how does the femoral n leave the pelvis?
passes through the psoas muscle and exits pelvis under the inguinal ligament, lateral to femoral triangle
what is in the femoral triangle?
femoral a, v, and lymphatic channels
what does the femoral n supply?
quadriceps muscles in anterior thigh
where does the femoral v terminate?
in long fine sensory branch
2 nerve roots of the lateral femoral cutaneous nerve?
L2,3
where does the lateral femoral cutaneous nerve lie?
lies on surface of iliacus muscle
how does the lateral femoral cutaneous nerve exit the pelvis?
under lateral end of inguinal ligament
what is the function of the lateral femoral cutaneous nerve?
purely sensory to lateral aspect thigh
what causes meralgia paraesthetica?
compression of the lateral femoral cutaneous nerve
nerve roots of the sciatic n?
L4-S3
what is the largest nerve in the body?
sciatic n
what is the main branch of the sacral plexus?
sciatic n
how does the sciatic n exit the pelvis?
through sciatic foramen below piriformis muscle
to which muscle does the sciatic nerve run deep?
gluteus maximus
which nerve supplies the hamstring muscles?
sciatic n
what does the sciatic n supply?
hamstring muscles, part of adductor magnus, and all lower leg and foot muscles via terminal branches
3 occasions when the sciatic n is at risk?
posterior dislocation of hip, IM injections, surgery
nerve roots of the common fibular nerve?
L4-S2
what is the smaller and lateral branch of the sciatic nerve?
common fibular n
what does deficit of common fibular nerve cause?
foot drop and slapping gait
most commonly injured nerve in lower limb?
common fibular nerve
where does the common fibular nerve lie?
passes around the lateral aspect of the neck of the fibula
what n is the communicating branch to the sural n?
common fibular n
which nerve divides to give rise to the superficial and deep fibular nerves?
common fibular nerve
