upper limb nerve injuries

Question 1

what condition would we be most likely to see in a mid shaft fracture of the humerus

Answer 1

wrist drop as it would damage the radial nerve

Question 2

what is the clinical presentation of wrist drop

Answer 2

a literal wrist drop, sensory loss on the dorsal 3.5 fingers minus the nail beds, digits remain flexed at the MCP joints

Question 3

why do we see wrist drop the way we do

Answer 3

the radial nerve has been damaged. hence we get sensory loss on the dorsal 3.5 fingers minus the nail beds.
the radial nerve supplies the posterior forearm so we get a loss of function in the extensor muscles, hence the wrist drop

Question 4

what condiotion are we like to see with compression at the gyon canal

Answer 4

we will see claw hand as we have distal compression of the ulnar nerve

Question 5

what are the clinical presentations of claw hand

Answer 5

This is where there is hyperextension of the MCP joint of little finger and ring finger and flexion at all IP joints.

Question 6

why do we see the claw hand

Answer 6

there has been damage of the ulnar nerve more distally. the ulnar nerve supplies the interossei and the medial two lumbricals. these are paralysed while all the long extensors and flexors in the forearm are normal. as the long extensors are fine we get extension at the MCP in all fingers. long flexors are intact which is why we see the IP flexion. due to the paralysis of the interossei and medial two lumbricals the action of the long muscles is unopposed so we get the MCP extension. this is for medial 2 fingers
the other two fingers are more straight as their lumbricals are fine

Question 7

what would we see from a compression in the cubital tunnel at the mediepicondyle of the humerus

Answer 7

we would see the paradoxical claw hand as the ulnar nerve is damaged in the forearm

Question 8

what are the clincial symptoms of paradoxical claw hand

Answer 8

claw hand where the IP joints are actually more upright, so a less severe claw hand

Question 9

why dop we see what we do in paradoxical claw hand

Answer 9

all the claw hand signs still persist. however as the nerve damage is higher we get paralysis of the FCU and the medial half of the flexor digitorum superficialis. as this part of the FDP is paralysed the lack of lumbircals doesn’t matter and there is now unopposed extensor action so the distal IP joints stand up a bit more than normal claw hand

Question 10

what condition will we see in a carpal tunnel syndrome

Answer 10

ape hand as there is distal damage to the median nerve

Question 11

what are the presentations of ape hand

Answer 11

loss of sensation in the palmar 3.5 fingers. but the thumb in opposed and cant move otherwise

Question 12

why do we see ape hand present the way it does

Answer 12

because the median nerve supplies the thenar muscles but the ulnar nerve supplies the opponens pollicis, this means the opponens pollicis has unopposed action and thus the thumb is stuck at the side

Question 13

what do we get when we have mid shaft fracture in forearm

Answer 13

median nerve damage higher up so potentially the hand of benediction

Question 14

what are the presentations of hand of benediction

Answer 14

when we ask them to make a fist the medial 2 fingers can do so but the other fingers stay extended

Question 15

why do we see hand of benediction the way we do

Answer 15

the median nerve supplies all the forearm muscles except for the flexor carpi ulnaris and the medial hald of the FDP. so when this muscle is paralysed we can no longer flex the lateral two fingers and the thumb, hence there is unpoosed extensor action on these fingers and they remain extended even when we try to make a fist.