Ulnar nerve palsy for PACES

There is wasting of the dorsal interossei causing dorsal 'guttering'.
There is wasting of the hypothenar eminence.
There is clawing of the 4th and 5th digits.
There is sensory loss over the medial 1.5 digits and corresponding part of the hand which does not extend proximal to the wrist.
Froments sign is present.

What causes do you know for an ulnar nerve palsy?
  • can be a lesion at any point from brachial plexus to the hand
  • compression: any mass at the elbow (eg boney mass in RA or OA, soft tissue mass), post operative or ITU stay
  • trauma (especially at medial epicondyle)
  • any cause of a mononeuropathy: diabetes, vasculititides (PAN, Wegeners), leprosy, amyloidosis...

What is the root of the ulnar nerve?
C8 and T1 

What do you mean by 'claw hand'?
Flexion of the interphalangeal joints and hyperextension of the metacarpophalangeal joints.

What is the function of the dorsal interossei?
Abduction of the fingers (recall D-AB and P-AD: dorsal abduction, palmar adduct)

What does the hypothenar eminence consist of?
Oppenes digiti minimi, Abductor digiti minimi and Flexor digiti minimi  

What muscles are innervated by the ulnar nerve?
  • C8: flexor carpi ulnaris, flexor digitorum profundus and superficialis to the ring and little fingers
  • T1: All intrinsic muscles of the hand except for the lateral 2 lumbicals, oppenens pollicis brevis, abductor pollicis brevis and flexor pollicis brevis (LOAF), which are innervated by the median nerve.

How can you tell a 'low' ulnar lesion from a 'high' lesion?
  • In a low lesion there is partial clawing of the hand as the lumbricals of the ring and little finger are paralysed causing MCP hyperextension whilst the flexor digitorum profundus is intact and causes DIP flexion.  Low lesions occur at the wrist.
  • In a high lesion the flexor digitorum pronfundus is also paralysed so the DIPs are not flexed, making the clawing less obvious.  High lesions usually occur at the elbow.

What is Froment's sign?
This is when the ulnar nerve is damaged so the adductor pollicis is paralysed, meaning that when a piece of paper is held between the thumbs and index fingers and pulled the paralysed thumb flexes.

What alternative diagnosis for a claw hand do you know?
  • Diabetic cheiropathy
  • Ischaemic contracture 
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