Ulnar nerve Lesion

Ulnar Nerve lesion
The ulnar nerve may be damaged at any point in its distribution. The most common sites are behind the elbow and in the hand.

The clinical features of an ulnar nerve lesion at the elbow include:
• wasting of the flexor carpi ulnaris and the ulnar half of the flexor digitorum:
-is apparent on the inner aspect of the flexor surface of the forearm
-weakness of flexor carpi ulnaris causes the hand to deviate to the radial side as the wrist is flexed
• wasting of the small muscles of the hand except the thenar eminence and the first two lumbricals
• clawing of the ring and little fingers (main en griffe):
-loss of the 3rd and 4th lumbricals and all the interossei results in:
-hyperextension of the metacarpophalangeal joints
-flexion of the interphalangeal joints
• paralysis of the hypothenar muscles:
-abolishes abduction of the little finger
• paralysis of the interossei:
-abolishes abduction and adduction of the fingers
• paralysis of the adductor pollicis:
-weakens adduction of the thumb which is most evident when a piece of paper is grasped in a pincer grip between thumb and index finger (Froment's sign)
• numbness and tingling:
-over the two ulnar fingers and the ulnar border of the palm

The clinical features of an ulnar nerve lesion below the elbow are presented according to the site of the lesion:
• in the cubital tunnel the features resemble those of a lesion at the elbow except:
-clawing is more prominent due to preservation of flexor digitorum profundus
-flexor carpi ulnaris is spared and so wrist flexion is unaffected
• at the wrist the features resemble those of a lesion at the elbow except:
-there is no sensory loss because the dorsal cutaneous branch of the ulnar nerve is spared
• in the hand the features resemble those of a lesion at the elbow except:
-the hypothenar eminence is usually spared
-wasting and weakness is confined to the interossei and adductor pollicis














Muscle and skin innervations of ulnar nerve
• Muscles:
o In the forearm, via the muscular branches of ulnar nerve:
-Flexor carpi ulnaris
-Flexor digitorum profundus (medial half)
o In the hand, via the deep branch of ulnar nerve:
-Hypothenar muscles
-Adductor pollicis
-The third and fourth lumbrical muscles
-Dorsal interossei
-Palmar interossei
o In the hand, via the superficial branch of ulnar nerve:
-Palmaris brevis
• Skin:
o The ulnar nerve also provides sensory innervation to the part of the hand corresponding to the fourth and fifth fingers:
-Palmar branch of ulnar nerve (anterior)
-Dorsal branch of ulnar nerve (posterior)