Clinical Cases Flashcards
What is the anatomical mechanism behind Erb’s Palsy?
Stretching of nerve roots C5 & C6 by abnormal increase in angle between the neck and the shoulder
What is the resulting deficit of an Erb’s Palsy?
Results in the upper limb hanging at the side, with medial rotation and the palm facing posteriorly
What is the resulting deficit from a lower brachial plexus injury (Klumpke palsy), affecting C8-T1 including the ulnar nerve?
Interosseous muscle atrophy and claw hand
What are the 5 terminal branches of the brachial plexus?
Axillary, musculocutaneous, median, ulnar and radial nerves
Where is the axillary nerve most at risk of injury?
As it courses posteriorly around the surgical neck of the humerus
What muscles does the axillary nerve supply?
Deltoid and teres minor muscles
What deficit could a fracture to the surgical neck of the humerus cause?
Inability to abduct the arm at the shoulder to a horizontal position and sensory loss in the shoulder patch area due to axillary nerve injury
What deficit does damage to the musculocutaneous nerve cause?
Weakness in supination and flexion of the shoulder and elbow
Where does the ulnar nerve course through the elbow?
Curves posterior to the medial epicondyle
Where does the ulnar nerve enter the forearm and what does it innervate?
Through the anterior compartment of the forearm where it innervates the flexor carpi ulnaris and the bellies of the flexor digitorum profundus to the ring and little fingers.
Where does the ulnar nerve enter the hand and what does it supply?
Through Guyon Canal superficial to the flexor retinaculum, supplying all the intrinsic muscles of the hand except for the three thenar muscles and lumbricals of the index and middle fingers
What deficit does ulnar nerve injury cause?
Radial deviation of the hand, weakness in flexion and adduction of the hand at at the wrist and loss of flexion at the DIP joint of the ring and little fingers. Also loss of abduction and adduction of the index, middle, ring and little fingers due to paralysis of the interossei muscles which causes a “Claw Hand”
Which muscles are primarily responsible for abduction at the shoulder and what nerves innervate them?
Deltoid and supraspinatus muscles, which are innervated by the axillary nerve and suprascapular nerves respectively.
What deficit would injury to the lateral cord of the brachial plexus cause and what muscles are affected? Given such an injury damages the musculocutaneous nerve?
Weakness of flexion at the elbow due to paralysis of the biceps brachii and brachialis muscles.
A patient sustains an injury to the lower brachial plexus. Which nerve will be most likely affected?
The C8 and T1 portions of the lower brachial plexus make up the majority of the ulnar nerve
What cord and nerve is injured causing a wrist drop?
The posterior cord, which supplies the radial nerve
A patient with a displaced fracture of the humerus complains of an inability to open their left hand and loss of sensation to a portion of the hand. What is the most likely diagnosis?
Injury to the radial nerve as it spirals around the humerus resulting in an inability to extend the wrist or fingers at the MCP joints and a loss of sensation of the lateral side of the dorsum of the hand, dorsum of the thumb and index and middle digits
Where is the radial nerve a particular risk of injury?
As it courses in the radial groove as it spirals around the midshaft of the humerus
What other structure courses the radial groove of the humerus besides the radial nerve?
The deep brachial artery
What two structures would a midshaft fracture of the humerus put at risk?
The radial nerve and the deep brachial artery
What are the two main terminal branches of the radial nerve and what do they do?
The deep branch of the radial nerve and the superficial branch of the radial nerve. The deep branch is entirely motor to the muscles of the posterior compartment of the forearm. The superficial branch is sensory to the dorsum of the hand and to the dorsum of the thumb, index finger and the radial side of the middle finger.
Describe the course of the radial nerve from the radial groove to the forearm.
It gives off multiple muscular branches to the triceps muscle in the posterior compartment, then pierces the lateral intermuscular septum to return to the anterior compartment of the arm, and descends to the level fo the lateral epicondyle of the humerus where it lies deep to the brachioradialis muscle where it divides into its two terminal branches.
What is the main blood supply to the upper limb?
Axillary artery -> brachial artery
Describe the course of the brachial artery
From the lower border of the teres major muscle and accompanies the median nerve on the medial aspect of the humerus. Towards the elbow it branches off the deep brachial artery which supplies the posterior compartment of the arm and passes around the radial groove of teh humerus with the radial nerve. It also has ulnar collateral branches to the elbow joint. The brachial artery shifts anteriorly as it enters the forearm lying just medial to the tendon of the biceps brachii muscle in the cubital fossa. At the level of the neck of the radius to divides into the ulnar and radial arteries.
