4 - Nerve Lesions Flashcards
What are the motor innervations of the ulnar nerve?
- The muscles of the hand (other than the thenar muscles and two lateral lumbricals)- Flexor Carpi Ulnaris - Medial half of flexor digitorum profundus
What are the sensory innervations of the ulnar nerve?
Innervates the anterior and posterior surfaces of the medial on and half fingers and the associated palm areas
In brief, give the course of the ulnar nerve
Passes down the medial side of the arm, passing posterior to the medial epicondyle to enter the forearm. At the the wrist the ulnar nerve travels superficially to the flexor retinaculum, forming the “ulnar tunnel”
What is the ulnar tunnel?
The ulnar tunnel is a space between the pisiform and hamate carpal bones, bridged by a piece of fibrous tissue from the flexor retinaculum.
How is the ulnar nerve damaged at the elbow?
Fracture of the medial epicondyle
What motor functions are lost if the ulnar nerve is damaged at the medial epicondyle?
Flexor carpi ulnaris and medial half of flexor digitorum profundus paralysed.
What sensory loss occurs in damaged elbow ulnar damage?
the anterior and posterior surfaces of the medial one and half fingers, and the associated palm area.
How is the ulnar nerve damaged at the wrist?
Lacerations to the wrist
What motor functions are lost to ulnar nerve damage at wrist?
Movement of the little and ring fingers is greatly reduced, due to paralysis of the medial two lumbricals.
What sensory functions are lost in ulnar damage to the wrist?
The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected. Sensory loss over palmar side of medial one and a half fingers only.
What occurs in long term ulnar damage?
Ulnar claw
What is ulnar claw?
hyper-extension of the metacarpophalangeal joints of the index and ring fingers – this is because of the paralysis of the medial two lumbricals, and the now unopposed action of the extensor musclesflexion at the interphalangeal joints (if the lesion has occurred close to the elbow, this might not be evident, as the flexor digitorum profundus will be paralysed)
What are the motor functions of the median nerve?
The flexor muscles in the forearm (with a few exceptions).Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.
What are the sensory functions of the median nerve?
Innervates the palm of the hands and posterior tips of the lateral three digits.
What is the basic course of the median nerve?
Descends down the arm lateral to the brachial artery.Halfway down arm, crosses over and travels medial Passes through cubital fossa, divides into branches and enters hand via carpal tunnel
What is carpal tunnel syndrome?
Median nerve can become compressed in carpal tunnel, due to thickening of synovial sheaths of tendons brought on by overuse.Causes pins and needles in sensors distribution of hand and weakness of thenar muscles
How is the median nerve damaged at the elbow?
Supracondylar fracture of humerus
What does damage to median nerve at elbow cause?
Hand of benediction - Flexors in forearm paralysed, so forearm constantly supinated and weak flexion. Flexion at thumb, index and middle finger impossibleLack of sensation over areas that median nerve innervates. .
What is the sensory innervation of the radial nerve?
Innervates most of the skin on the posterior side of the forearm and the dorsal surface of the lateral side of the palm and the lateral three fingers
What are the motor functions of the radial nerve?
Innervates the triceps brachii, responsible for extension at the elbowInnervates the majority of the extensor muscles in the forearmResponsible for extension of wrist and fingers and supination of the forearm
What is the course of the radial nerve?
Passes out of the axilla posteriorly and descens down the arm via the radial groove on the posterior shaft of the humerus. Travels anteriorl over the lateral epicondyle of the humerus through the cubital fossa and into the forearm.
How can the radial nerve be damaged at the axilla? What does it cause?
Dislocation of the humerus at the glenohumeral joint, or excessive pressure on the axilla. Causes wrist drop and lack of sensation.
How can the radial nerve be damaged in the radial groove? What does it cause?
Mid-shaft fractureCauses wrist drop and sensory loss on dorsum of hand
How can the deep branch of radial nerve be damaged?
DISLOCATION OF RADIUS AT ELBOW
How can damage to superficial radial nerve occur?
Stabbing or laceration of the forearmCauses loss of sensation in dorsum of hand
What are the sensory functions of the axillary nerve?
Innervates regimental badge area
What are the motor functions of the axillary nerve?
Innervates teres minor and deltoid
What is the quadrangular space?
A route for nerves and vessels to pass from anterior arm to posterior. Axillary nerve and posterior circumflex humeral artery pass.
How can axillary nerve be damaged?
Anterior dislocation of the humerus at the glenohumeral joint, or a fracture of the humerus at the surgical neck.
What are the effects of axillary nerve be damaged?
Paralysis of deltoid and teres minor muscles. Loss of innervation to regimental badge area,
What is a characteristic clinical sign of long term axillary damage?
Paralysed deltoid muscle atrophies and the greater tuberosity can be palpated.
What are the motor functions of the musculocutaneous nerve?
Anterior compartment of the arm - BBC
What are the sensory functions of the musculocutaneous nerve?
Innervates skin on the lateral surface of the forearm
What is the course of the musculocutaneous nerve?
Arises from lateral cord of brachial plexus - leaves the axilla and pierces coracobrachialis. Then passes down the arm, anterior to brachialis and posterior to biceps. Emerges through cubital fossa laterally to biceps tendon and continues into the forearm as the lateral cutaneous nerve
How can the musculocutaneous nerve be damaged? What occurs?
Shank to the axillaFlexion at shoulder and elbow and supination weakened. Loss of sensation over lateral side of forearm
