Radial And Median Nerves

Radial and median nerves  Radial

nerve is the largest branch of the posterior cord of brachial plexus and is regarded as the continuation of the posterior cord.  C5,6,7,8(T1)

COURSE

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In the axilla - lies posterior to 3rd part of the axillary artery and anterior to 3 muscles, subscapularis,teres major and latissimus dorsi. Passes the lower triangular space to enter the back of the arm.

Branches before entering the spiral groove  Muscular-

to long head and medial head of triceps (ulnar collateral nerve).  Cutaneous branch - posterior cutaneous nerve of the arm.

In the spiral (radial groove) groove 

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Passes between medial and lateral heads of triceps in the groove. Supplies lateral and medial heads and anconeus (a detached part of medial head). Cutaneous brancheslower lateral cutaneous branch of the arm and posterior cutaneous nerve of forearm. Accompanied by profunda brachii artery.

After leaving the groove  Pierces

the lateral intermuscular septum and comes to lie in the radial tunnel.  Radial tunnel is the space between brachialis and brachioradialis.  Can be trapped here.

In the cubital fossa (deep to brachioradialis)   

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Lies between brachialis and brachioradialis. Supplies brachioradialis and ext.carpi.rad.longus. Gives proprioceptive fibers (only) to brachialis.(?) Divides into superficial and deep branches. (deep branch is called posterior interosseous nerve). Superficial branch is purely sensory!!!

Posterior interosseous nerve  Supplies

all the muscles in the extensor compartment of forearm (back of forearm) including supinator.

Radial nerve injuries

Saturday night palsy?

Extension at the elbow is not affected!!! Why?

On the hand (sensory supply)

1.Ulnar nerve 2.Median nerve 3.Radial nerve

The dorsum of the hand, sensory innervation

Part time job in the arm Full time in the fore arm Holiday in the hand!! (regarding the muscular supply)

Median nerve 

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Arises by two roots from the corresponding cords, lateral root and medial root. In the axilla lies in front of the axillary artery. In the front of the arm, it gradually crosses the brachial artery from lateral to medial (superficially).

Roots of median nerve unite in front of the axillary artery.

In the cubital fossa  From

lateral to medial:  Tendon of biceps  Artery (brachial)  Nerve (median)  under cover of bicipital aponeurosis.  (Essential to remember!!!)

In the forearm  Enters

the forearm between the two heads of pronator teres (do remember!!!).  It can be trapped here leading to “PRONATOR SYNDROME”.  Runs deep to the FDS till the wrist and enters the carpal tunnel by curving medial to Flexor carpi radialis.  In the palm it divides into medial and lateral branches.

distribution  No

branches in the arm (holiday in the arm!!)  Supplies all the superficial flexors of the forearm except Fl.Carpi ulnaris.  Supplies the deep group (Fl.dig.profundus (lateral half),FPL and Pronator quadratus through its deep branch called “anterior interosseous nerve”.  (Full time job in the forearm!!!!)

In the hand  Supplies

thenar eminence (abductor pollicis brevis,flexor pollicis brevis and opponens pollicis)  and 1st and 2nd lumbricals.  Mostly it is sensory in the hand.

Brachial plexus & median nerve

Part time job in the hand!!!!

palm

1.Ulnar nerve 2.Median nerve 3.Radial nerve

The dorsum of the hand, sensory innervation

Clinical aspects  Can

be compressed between the two heads of pronator teres.  Usually compressed in the carpal tunnelCARPAL TUNEL SYNDROME(CTS).

Injury

Injury of median nerve at different levels causes different syndromes Injury of this nerve at a level above elbow joint results in loss of pronation and a decrease in flexion of the hand at the wrist joint.

In the hand, thenar muscles are paralyzed and atrophy in time. Opposition and flexion movements of thumb are lost, and thumb and index finger are arrested in adduction and hyperextension position. This appearance of the hand is collectively referred as ape hand deformity. (ape thumb deformity)

In addition, in palmar side of the hand sensation of lateral part of hand, first three fingers and lateral half of the fourth finger and in dorsal side sensation of distal portions of first three fingers and lateral half of distal portion of fourth finger is lost.

Which of the following muscles can perform arm and elbow flexion along with forearm supination? (A) biceps brachii (B) brachialis (C) brachioradialis (D) coracobrachialis (E) supinator

Which of the following innervates the muscle identified? (A) median (B) Musculocutaneous (C) Radial (D) suprascapular (E) ulnar

A 24-year-old student is brought to the emergency room after being found in a ditch where he had lain overnight after being hit by a car. He complains of severe pain in the left arm and examination reveals a broken humerus. Neurological examination reveals that the patient can extend the elbow but displays inability to supinate the elbow when it is extended. The patient also has wrist drop and very weak hand grasp. The neurological lesion is likely localized at which of the following locations?

(A) posterior cord of the brachial plexus (B) posterior divisions of the brachial plexus (C) radial nerve at the distal third of the humerus (D) radial nerve at the mid forearm (E) radial nerve at the wrist

In the above patient, when the elbow is partially flexed, the patient can supinate the left forearm. This is due to the function of which of the following? (A) biceps brachii (B) brachialis muscle (C) brachioradialis (D) pronator teres (E) anconeus

A 42-year-old man visits his doctor after his cousin, who has not seen him for years, notices a change in his appearance. Overgrowth of his frontal bones and enlargement of his hands and feet have occurred. The patient complains of a tingling sensation in the 1st, 2nd, and 3rd digits of the right hand and loss of coordination and strength of the right thumb. Which of the following nerves has most likely been affected? A. Anterior interosseous nerve B. Median nerve C. Musculocutaneous nerve D. Radial nerve

A patient complains to his physician that his thumb "doesn't work right." The physician notes weakness of the thumb in extension, although rotation, flexion, abduction, adduction, and opposition are normal. Which of the following nerves is most likely involved? A. Median and radial B. Median and ulnar C. Median only D. Radial only E. Ulnar only