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Radial Nerve

  1. Radial nerve is the largest branch of brachial plexus and is the continuation of posterior cord(root value C5-8, T1)
  2. The various branches of radial nerve are: -
    1. Before spiral groove: - Medial muscular branches to the long and medial head of triceps. Here triceps also gives posterior cutaneous nerve of arm.
    2. In the spiral groove: - Posterior muscular branch to lateral &medial head of triceps and direct branch to anconeus. Sensory branches in this area are posterior cutaneous nerve of forearm and lateral cutaneous nerve of arm.
    3. At lower end of spiral groove (before elbow): - Muscular branches to Branchioradialis, Extensor carpi radialis longus.
    4. After crossing the elbow, before piercing the supinator: - Extensor carpi radialis brevis and the supinator.
    5. After piercing the supinator: - Extensor digitorum, extensor digiti minimi, Extensor Carpi ulnaris, Abductor pollicis longus, extensor pollicis brevis, Extensor pollicis longus, extensor indicis.
  3. Among these muscles, radial nerve directly supplies triceps, anconeus, brachioradialis, and extensor carpiradialis longus. All the other muscles are supplied by deep branch of radial nerve, i.e., posterior interosseous nerve.


Radial nerve injury

Radial nerve injury may be high or low.

  1. High radial nerve palsy
    1. Injury is before the spiral groove
    2. All muscles supplied by radial nerve are paralysed.
  2. Low radial nerve palsy
    1. Injury is after the spiral groove.
    2. Low radial nerve palsy may be of two types.
      1. Type I: - Injury occurs between the spiral groove and elbow joint. Muscles involvement is : -
        a) Elbow extensors (Triceps, anconeus) are spared.
        b) Wrist, elbow and finger extensors are paralysed.
        c) Sensory loss in first web space (on dorsal side)
      2. Type II: - Injury occurs below the elbow joint.
        a) Elbow extensors (triceps, anconeus), brachioradialis and wrist extensors (ECRL) are spared,
        b) Finger extensors (extensor digitorum, extensor digiti minimi, extensor indicis),ECRBand thumb extensors (extensorpollicis longus & brevis) are paralysed.
        c) Sensory loss in first web space (on dorsal side).

Clinical features of radial nerve palsy

  • Clinical features depend upon the site of lesion.
  1. If lesion is high
    1. Wrist drop, thumb drop and finger drop.
    2. Inability to extend elbow, wrist, thumb & fingers (MP joint)
    3. Patient can extend interphalangeal joints due to action of lumbricals and interossei.
    4. Sensory loss over posterior surface of arm & forearm and lower lateral half offorearm.
  2. Iflesion is low

a. Type - I

b. Type- II

i. Wrist drop, thumb drop and finger drop.

i. Thumb drop and finger drop

ii. Elbow extension is preserved.

ii. Elbow and wrist extension is preserved

iii. Sensory loss over the dorsum of first web space.

iii. Sensory loss over the dorsum of first web space


Clinical features of posterior interosseous nerve

  1. It is prone to be injured in injury & operations of radial head- neck.
    There is no sensory deficit as it is a pure motor nerve.
  2. Wrist extension is preserved (i.e. no wrist drop) due to spared extensor carpi radialisIongus.
  3. Presents with loss of extension of metacarpophalangeal(MP) joints i.e., thumb &finger drop.

Saturday night palsy (weekend palsy)

  1. In this condition, there is compression of the radial nerve between spiral groove and the lateral intermuscular septum.
  2. It is known after an event which typically happens on a Saturday night weekend when in an inebriated condition, a person slump with his mid-arm compressed between the arm ofthe chair and his body.

Axillary nerve (circumflex nerve)

  1. Axillary nerve is a branch ofthe posterior cord of brachial plexus with root value C5 and C6. It leaves the posterior wall of axilla along with the posterior circumflex humeral vessels through the quadrangular space. While passing through the quadrangular space it gives its first branch, an articular twig to the shoulder joint. Then it divides into-
    1. Anterior division: - Winds around the surgical neck of humerus to supply deltoid.
    2. Posterior division :- It gives of
      1. Branches to posterior part of deltoid.
      2. Nerve to teres minor which shows pseudo ganglion.
      3. Upper lateral cutaneous nerve of arm supplying the skin covering lower part of deltoid (regimental badge region).
  2. Damage to axillary nerve causes deltoid paralysis, teres minor paralysis, loss of rounded contour of shoulder, sensory loss in small patch of skin and on the outer surface of arm immediately above the deltoid tuberosity (regimental badge patch). There is loss of abduction from 150-900 due to paralysis of deltoid (first 15° of flexion is not lost as it is caused by supraspinatus and overhead abduction is preserved as it is caused by trapezius and serratus anterior).

Musculocutaneous nerve

It is a branch of lateral cord of brachial plexus with root value C5, 6,7.It supplies Biceps brachii, corachobrachialis andbrachialis. After supplying these muscles, musculocutoneous nerve continues as lateral cutaneous nerve offorearmsupplying the skin oflateral border of forearm. Damage to musculocutaneousnerve results in:-

  1. Weakness of flexion of elbow due paralysis of biceps and brachialis.
  2. Loss of supination of semi flexed forearm due to paralysis of biceps.
  3. Sensory loss along the lateral (radial) border of forearm.
  4. Loss of biceps jerk.

Carpal tunnel syndrome

Carpal tunnel syndrome is the most common and widely known entrapment neuropathy in which the body's peripheral nerve is compressed or traumatized. Carpal tunnel syndrome occurs when the median nerve is compressed in the carpal tunnel below flexor retinaculum. The carpal tunnel is a narrow rigid passage way of ligament and bones at the base of hand, in front of distal part of wrist. Carpal tunnel houses the median nerve and 9 tendons.


Clinical features of carpal tunnel syndrome

  1. Symptoms usually start gradually, with frequent burning, tingling, paraesthesiaand numbness in the distribution of median nerve, i.e., lateral three & half of fingers and lateral2/3rd of palm.
  2. Sensory symptoms can often be reproduced by percussing over median nerve (Tinel's sign) or by holding the wrist fully flexed for a minute (Phalen's test).
  3. As the disease progresses, clumsiness of hand and impairment of digital function develop.
  4. Later in the disease, there is sensory loss in median nerve distribution and obvious wasting of thenar



Median (anterior interosseous)







Radial (posterior interosseous)


(superficial radial)



Carpal tunnel

Proximal forearm

Pronator teres

Ligament of Struthers

Cubital tunnel

Guyon's canal


Spiral groove

Proximal forearm


Distal forearm

Suprascapular notch

Usually referred to as

Carpal tunnel syndrome

Anterior interosseous syndrome

Pronator teres syndrome

Ligament of Struthers syndrome

Cubital tunnel syndrome

Guyon's canal syndrome

Radial nerve compression

Radial nerve compression

Posterior interosseous nerve


Wattenberg's Syndrome

Suprascapular nerve entrapment

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