Brachial Plexus Flashcards
What innervates the anterior compartment of the brachium/upper arm (biceps and brachialis muscles) and what action does this mean these muscles perform?
Musculocutaneous nerve
The muscles perform flexion
What innervates the posterior compartment of the bracium/upper arm (triceps) and what action does this mean these muscles perform?
The Radial nerve
Muscles perform extension
What innervate the anterior compartment of the forearm (antebrachium) and hand?
The Ulnar nerve and Median nerve
What innervates the posterior compartment of the forearm (antebrachium) and hand?
The Radial nerve
A patient falls off of a ladder and lands on his shoulder causing a forceful increase in the angle between his head and neck. He presents with his arm stuck in an adducted, internally rotated position with his hand stuck in pronation. What spinal nerve root is most likely injured in this patient and what is the spinal dysfunction called?
C5 and C6 - Superior Trunk injury (Erb’s Palsey)
This describes the “Waiter’s tip” arm position
A patient presents with his MCP joints hyperextended and his PIP/DIP joints stuck in flexion. His wrist is also extended, creating his hand to be stuck in a claw-like position. What spinal nerve root is most likely damaged, what nerves are involved, and what is the spinal dysfunction called?
C8 and T1 - Inferior Trunk injury (Klumpke’s Palsey)
This describes “claw hand”/”ulnar claw” - the Median and Ulnar nerves are affected. Often due to forceful abduction of arm
A patient presents for a check-up on her knee. She has been using crutches for the last month due to her knee injury, and your physical exam reveals that she has weakness when pushing away with her arm and difficulty extending her wrist and fingers. What is causing this?
Impingement of the Radial nerve in the axillary region - describes “wrist drop” posture
A patient presents to the ER after falling on his arm. Since the fall, his hand has been stuck in a flexed position. Physical exam shows that he retains extension capabilities in his posterior arm. What specific injury has this patient sustained, and how do you know?
A mid-shaft humeral in the radial groove (spiral groove) region
You know this because the patient retains strength in his triceps (arm extensors) but still resembles wrist-drop position, so the radial nerve injury had to occur mid-shaft or below to allow innervation of that area. An axillary region Radial nerve injury knocks out extension in the entire arm/forearm.
If a patient has numbness in the posterior deltoid region, difficulty abducting his arm, and has diminished lateral rotation of his arm, what nerve is most likely injured and what are a few common causes of these symptoms?
Axillary Nerve injury (C5, C6)
Fracture to surgical neck of humerus, anterior dislocation of glenohumeral joint, and/or a rotator cuff repair surgery
A patient cannot raise his arms above 90 degrees and has raised scapula. What nerve is most likely injured in this patient?
The Long Thoracic nerve – “winged scapula” is a dead giveaway
Numbness and tingling in the 4th and 5th digits, weaking of grip/loss of finger flexion, and loss of ab- and adduction of the 4th and 5th fingers indicates what injury has occurred, and what are two common reasons for this?
The Ulnar nerve
Causes: Fracture to medial epicondyle of humerus and/or entrapment of the ulnar nerve in the cubital tunnel
What injury is indicated by the inability to flex 2nd and 3rd digits when making a fist (“Hand of Benediction”), thenar eminence atrophy, and loss of ab- and adduction of digits 1-3? What are a few examples of injuries that cause these symptoms?
Median nerve injury
Causes: fracture of humerus above the condyles, entrapment of the Median nerve by pronator teres, and/or inflammation/irritation in the carpal tunnel (Carpal Tunnel Syndrome)
What cutaneous innervation of the hand is the ulnar nerve responsible for?
The palmar AND dorsal sides of the hand leading all of the way up to the 5th digit and the medial half of the 4th digit
What cutaneous innervation of the hand is the median nerve responsible for?
The palmar side of hand all the way up the hand thru digits 1-3.5 –> remember: the median nerve runs thru the Carpal Tunnel on the palmar side of the hand!
What cutaneous innervation of the hand is the Radial nerve responsible for?
The palmar side of hand all the way up the hand thru digits 1-3.5
