Ulnar Nerve

00:01 So, now, let's look at lesions that impact the ulnar and the radial nerves.

00:07 Let's start off with the ulnar and remind ourselves of the course of the ulnar nerve, coming to direct continuation of the medial cord of the brachial plexus.

00:15 So, here, we have the ulnar nerve. It runs medial to the brachial artery and it penetrates the medial intermuscular septum here as it then, passes posterior to the medial epicondyle of the humerus in what's known as the groove of the ulnar nerve.

00:30 Once it's passed through that, it then runs alongside the medial aspect of the muscles within the forearm, specifically, flexor digitorum profundus and by separating flexor digitorum profundus and flexor carpi ulnaris, you can reveal the ulnar nerve.

00:45 The ulnar nerve then extends into the hand, not via the carpal tunnel, but by the Guyon's canal.

00:51 And this happens medial to the carpal tunnel.

00:54 Once it's there, it gives off to a deep branch that goes and supplies the interosseous muscles and it also supplies various other muscles within the hand that we've spoken about.

01:03 So, adductor pollicis medial two lumbricals, interossei and the hypothenar muscles.

01:10 So, remembering this is important when we have a lesion of the ulnar nerve, the sort of muscular deficiencies we're going to have.

01:17 It also gives rise to a superficial branch which goes on to supply palmaris brevis muscle.

01:22 But it also importantly has a cutaneous supply.

01:26 It supplies the palmar surface of the little finger and the medial half of the ring finger.

01:31 Those areas not supported by the median nerve.

01:36 It also supplies those structures on the dorsal surface of the hand, the little finger and the ring finger.

01:44 A common site of location is at that groove around the medial epicondyle.

01:48 So, fractures in this location or if you ping your funny bone can lead to a funny sensation around the distribution of the ulnar nerve.

01:57 So, damage at the level of the groove of the ulnar nerve, all compression at Guyon's canal.

02:02 This can lead if it's damaged at the level of the ulnar nerve to paralysis of most of the intrinsic muscles of the hand and also, those associated within the forearm.

02:11 Remember, there's some aspects of the forearm muscles which is supplied by the ulnar.

02:15 You'll also end up with sensory loss in the medial palm and the medial one and a half fingers.

02:21 So, the opposite area to that of the median nerve.

02:24 Similar to the hand of benediction, you have the opposite occurring now where you have claw hand.

02:29 Remember, the ulnar nerve is supplying a medial two digits enabling them to flex.

02:36 Here, we can see that with claw hand, when you ask the patient to form a fist, the median nerve is still intact and that can cause these fingers to flex whereas the innervation of these fourth and fifth digits is now compromised, they remain extended.

02:52 And this is what's known as claw hand, flexion of the first, second, and third digits because of the intact median nerve.

02:58 Damage to the ulnar nerve means the fourth and fifth fingers remain extended.