Myotomes, dermatomes, peripheral nerves Flashcards
What is the sensory distribution of the Median nerve?
Thumb, index finger, middle finger, lateral aspect of fourth finger and palm.
What is the motor distribution of the median nerve?
Thenar muscles, lateral lumbricals, flexion of the elbow, flexion of the wrist (apart from flexor carpi ulnaris), flexion of the fingers. - Basically all flexion in hands and arms.
What is the sensory distribution of the ulnar nerve?
What is the motor function of the ulnar nerve?
All the intrinsic muscles of the hand except for three thenar muscles, and flexor carpi ulnaris. Also does flexor digitorum superficialis which attaches to DIPs
What will an ulnar nerve injury cause?
Clawing of the hand, especially on the ulnar side due to lack of extension muscles. sensory changes over the palmar aspect of the little finger and half of the fourth finger.
How can you tell the difference between an ulnar nerve injury at the elbow or the wrist?
Elbow - loss of sensation over the dorsal surface of the hand on the median side, preserved in wrist injury
What is the sensory supply of the axillary nerve?
Saergents patch over shoulder
What is the motor function of the axillary nerve?
paralysis of deltoid – very weak shoulder abduction from 15-90°; weak shoulder flexion and extension
paralysis of teres minor – weak shoulder external rotation
What is the nerve root supply of the axillary nerve?
What injury is classically associated with damage to axillary nerve and why?
Fractured head of humerus, as axillary nerve wraps around head of humerus
What is the nerve root origin of the radial nerve?
C5 to T1
What is the sensory function of the radial nerve?
Posterior arm and forearm
lateral ⅔ of dorsum of hand
proximal dorsal aspect of lateral 3 ½ fingers (thumb, index, middle and half of ring finger)
- Basically extensor surfaces of arm and hand
What is the motor function of the radial nerve?
posterior compartment of arm
triceps – extends and adducts shoulder, extends elbow
posterior compartment of forearm
brachioradialis – flexes elbow
anconeus – extends elbow, stabilises elbow joint
supinator – supinates forearm
extensor carpi radialis longus and brevis – extend and abduct wrist
extensor carpi ulnaris – extends and adducts wrist
extensor digitorum, extensor pollicis longus and brevis, extensor indicis and extensor digiti minimi – extend thumb and fingers at MCPJs and IPJs
abductor pollicis longus – abducts thumb
Basically all extension of arm and hand
What are some common mechanisms of injury to the radial nerve?
Saturday night palsy/crutch palsy - prolonged pressure on inside of arm.
Stab wounds (including venesection!) in antecubital fossa
Injury to what nerve causes wrist drop? What is this?
WRIST DROP” deformity at rest and on attempted wrist extension – the patient cannot extend their wrist/fingers, resulting in unopposed wrist flexion. In the classical description of a radial nerve injury, the forearm is also pronated, the fingers are flexed and the thumb adducted.