Nerves

Question 1

Posterior interosseous nerve

Answer 1

Emerges from supinator between the superficial extensor muscles and lowest fibres of supinator
It gives recurrent branches which innervate extensor digitorum, extensor digiti minimi and extensor carpi ulnaris
It then passes with the posterior interosseous artery superficial to the abductor pollicis longus supplying it.
It supplies branches to extensor pollicis longus and brevis and extensor indicis and ends as a small gangliform enlargement at the back of the carpus from which the intercarpal joints are supplied.

Question 2

Ulnar nerve - origin, path, muscles supplied

Answer 2

Origin - C8, T1

Supplies (no muscles in the upper arm)
Flexor carpi ulnaris
Flexor digitorum profundus
Flexor digiti minimi
Abductor digiti minimi
Opponens digiti minimi
Adductor pollicis
Interossei muscle
Third and fourth lumbricals
Palmaris brevis

Path
Posteromedial aspect of upper arm to flexor compartment of forearm, then along the ulnar. Passes beneath the flexor carpi ulnaris muscle, then superficially over the flexor retinaculum into the palm of the hand.

Question 3

Ulnar nerve injury

Answer 3

Damage at the wrist:
Wasting and paralysis of intrinsic hand muscles (claw hand)
Wasting and paralysis of hypothenar muscles
Loss of sensation medial 1 and half fingers

Damage at the elbow:
Radial deviation of the wrist
Clawing less in 4th and 5th digits

Question 4

Branches of ulnar nerve

Answer 4

Branches
Muscular branch - Flexor carpi ulnaris, Medial half of the flexor digitorum profundus
Palmar cutaneous branch (Arises near the middle of the forearm) - Skin on the medial part of the palm,
Dorsal cutaneous branch - Dorsal surface of the medial part of the hand
Superficial branch - Cutaneous fibres to the anterior surfaces of the medial one and one-half digits
Deep branch - Hypothenar muscles, All the interosseous muscles, Third and fourth lumbricals, Adductor pollicis, Medial head of the flexor pollicis brevis

Question 5

Median nerve - origin and path

Answer 5

Formed by the union of a lateral and medial root respectively from the lateral (C5,6,7) and medial (C8 and T1) cords of the brachial plexus
The nerve descends lateral to the brachial artery, crosses to its medial side (usually passing anterior to the artery). It passes deep to the bicipital aponeurosis and the median cubital vein at the elbow.
It passes between the two heads of the pronator teres muscle, and runs on the deep surface of flexor digitorum superficialis (within its fascial sheath).
Near the wrist it becomes superficial between the tendons of flexor digitorum superficialis and flexor carpi radialis, deep to palmaris longus tendon. It passes deep to the flexor retinaculum to enter the palm, but lies anterior to the long flexor tendons within the carpal tunnel.

Question 6

Branches of median nerve

Answer 6

Upper arm - No branches, although the nerve commonly communicates with the musculocutaneous nerve
Forearm - Pronator teres, Pronator quadratus, Flexor carpi radialis, Palmaris longus, Flexor digitorum superficialis, Flexor pollicis longus, Flexor digitorum profundus (only the radial half)
Distal forearm - Palmar cutaneous branch
Hand (Motor) - Motor supply (LOAF) - Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
Hand (Sensory) - Over thumb and lateral 2 ½ fingers, on the palmar aspect this projects proximally, on the dorsal aspect only the distal regions are innervated with the radial nerve providing the more proximal cutaneous innervation

Question 7

Median nerve injury

Answer 7

Damage at wrist

• carpal tunnel syndrome
• paralysis and wasting of thenar eminence muscles and opponens pollicis (ape hand deformity)
• sensory loss to palmar aspect of lateral (radial) 2 ½ fingers

Damage at elbow, as at wrist plus:

• unable to pronate forearm
• weak wrist flexion
• ulnar deviation of wrist

Anterior interosseous nerve (branch of median nerve):

• leaves just below the elbow
• results in loss of pronation of forearm and weakness of long flexors of thumb and index finger

Question 8

Superior laryngeal nerve

Answer 8

Innervates the cricothyroid muscle
Since the cricothyroid muscle is involved in adjusting the tension of the vocal fold for high notes during singing, SLN paresis and paralysis result in abnormalities in pitch and/or inability to sing with smooth change to each higher note (glissando or pitch glide)

Question 9

Recurrent/Inferior laryngeal nerve

Answer 9

Innervates intrinsic larynx muscles which controls:

a. Opening vocal folds (as in breathing, coughing)
b. Closing vocal folds for vocal fold vibration during voice use
c. Closing vocal folds during swallowing

Question 10

Sciatic nerve - origin, termination, muscular branches, sensory branches, articular branches

Answer 10

Origin - L4-S3

Articular branches - Hip joint

Muscular branches in upper leg

• semitendinosus
• semimembranosus
• biceps femoris
• part of adductor magnus

Cutaneous sensation

• posterior aspect of thigh via cutaneous nerves
• gluteal region
• entire lower leg except the medial aspect

Termination - upper part of the popliteal fossea by dividing into the tibial and peroneal nerves