RADIAL NERVE Dr. Qudsia Sultana
Objectives Origin Course & Relations Branches Distribution Applied Anatomy
Radial Nerve Originates as the terminal branch of the posterior cord of the brachial plexus Roots from C 5, 6, 7, 8, & T 1. Largest branch of brachial plexus It is primarily a motor nerve
Course – RN – Ant. view-Axilla It commences its decent into the arm by passing anterior to the muscles forming posteerior wall of axilla.
Course of Radial Nerve Enters lower triangular interval Teres major (superior) Long head triceps (medial) Humerus (lateral)
Course of R N Comes to lie in distal part of spiral groove with profundi brachii artery Beneath lateral head of triceps and proximal to origin of medial head
Course of Radial Nerve The lower portion of the radial nerve pierces the lateral intermuscular septum at approximately 812 cm from the lateral epicondyle and enters the lower part of arm
Course of Radial Nerve In anterior compartment of arm lies between brachialis medially and brachioradialis, Extensor carpi radialis longus laterally. In the cubital fossa divide Superficial radial Deep radial /Posterior interosseous nerve
Course of Superficial Radial Nerve Runs down the forearm along the lat. border of BR with radial artery on its ulnar side in the middle 1/3 of forearm Passes posteriorly through tendon of BR proximal to radial styloid.
Course of Superficial R. Nerve Passes over tendons of snuffbox Terminates as cutaneous branches to dorsum of hand lateral 3 1/2 digits except nailbeds
Course – Posterior Interosseous Nerve The Post Interosseous Nerve continues down the forearm dividng between the heads of supinator and then emerging to split into several branches that supply the extensors of the wrist and hand
Lesions Level I – Axilla Level II – Spiral groove Level III – Elbow Level IV – Forearm
Axilla Lesions in the axilla Involves the posteriorcord / high axillary lesions. * Etiology: Crutches / shoulder dislocation
Position • Hand hangs in flexion(wrist drop) • Wasting of dorsal arm (triceps)& muscle mass on the posterior surface of the forearm • Paraesthesias & sensory loss on the entire extensor surface of the arm & forearm & on the back of the hand & dorsum of the first 4 fingers.
Spiral Groove Etiologies Humeral factures/Compressive lesions / Saturday night palsy Entrapment by tendinous arch of lateral head of triceps muscle/damaged after arm excercise. Soldiers developing palsies at the lateral border of humerus after military shooting training Sensibility on the extensor aspect of arm is spared. Sensibility on the extensor aspect of forearm may or may not be spared. Wrist drop + / No loss of elbow extension
Elbow – Radial Tunnel Syn. • Involvement of the Post Interosseous N. • Etiologies A constricting band at the radiohumeral joint capsule.
Position Atrophy & paresis of the ECU, ED, Extensor digiti minimi APL, EPB & extensor indices. Extensor carpi radialis is intact. • Drop finger deformity Difficulty in extending the MCP of all five fingers Partial wrist drop No sensory loss The wrist deviates radially, when the patient makes a fist.
Cheiralgia Paresthetica • The superficial cutaneous branch of the radial nerve → pure sensory syndrome that affects the radial part of the dorsum of the hand & dorsal aspect of the first 3 ½ fingers. • Etiology: Crushing/twisting injuries of the wrist/forearm ( “Hand-cuff / Wrist watch neuropathy” ) Repetitive pronation & supination.
Summary Radial nerve arises from posterior cord of the brachial plexus It passes posterior to the axillary artery between long and medial heads of triceps muscle, to lie in the spiral groove between medial & lateral heads of triceps muscle. Here it is accompanied by the profunda brachii artery before it pierces lateral intermuscular septum of the lower third humerus to run between brachialis & brachioradialis At the lateral of epicondyle humerus, it gives rises to PIN & superficial radial nerve
Radial nerve supply all the extensor muscles of forearm & arm. However it also supply brachioradialis, which is flexor of elbow when forearm pronated. Damage to the nerve in the spiral groove causes wrist drop but no loss of elbow extension, as fibres of triceps remain intact proximal to this site. Only damage in the axilla will causes loss of elbow extension & wrist drop Damage to posterior interosseus nerve (PIN) does not cause wrist drop because extensor carpi radialis longus receives its innervation from the main radial nerve Pin only causes inability to extend metacarpophalangeal joint finger drop.