Ulnar Nerve Palsy 2018-01-30T16:37:12+00:00

Nerve supply

  • Motor
    • Forearm
      • Flexor carpi ulnaris
      • Medial half of flexor digitorum profundus (distal interphalangeal joint)
    • Small muscles of the hand
      • Abductor digiti minimi
      • Opponens digiti minimi
      • Flexor digiti minimi
      • Medial two lumbricals
      • Interosseous muscles
      • Adductor pollicis
  • Sensory
    • Palmar and dorsal aspects of medial 1½ fingers

Examination

  • Inspection
    • Wasting of the hypothenar eminence
    • Ulnar claw, especially when opening hand
      • Results from unopposed extension of the MCPJ (paralysis of medial two lumbricals) and flexion of the DIPJ (medial half of FDP)
      • Ulnar paradox: lesions at the wrist result in a more deformed claw. More proximal lesions will paralyse the medial half of FDP, reducing the flexion deformity when the patient is asked to extend his fingers
    • Scars / deformities / fractures at elbow and wrist
  • Power
    • Finger abduction
    • Finger adduction
    • Thumb adduction (best to test in extension)
      • Froment’s sign: ask the patient to hold a piece of paper between an extended thumb and the adjacent index finger. Pull the paper out of this pincer grip – the sign is positive if the patient flexes or abducts the thumb to main his grip on the paper.
    • Fourth and fifth finger FDP power (fix middle phalanx, ask patient to flex DIPJ)
      • If preserved, lesion is distal
    • Wrist flexion in the ulnar direction (FCU)
  • Sensation
    • Numbness over ulnar 1½ digits
    • Numbness over the radial half of the 4th finger implies a C8 lesion, not an ulnar lesion

Differential diagnosis

  • C8 / T1 palsy
  • Cervical syringomyelia

 Causes of ulnar nerve palsy

  • Lesions at the elbow
    • Fracture
    • Arthritis / osteophytes
    • Compression during surgical procedure
    • Compression from prolonged leaning on a flexed elbow
    • Cubital tunnel syndrome
  • Lesions at the wrist
    • Hook of hamate fracture
    • Lacerations
    • Repetitive strain injury (e.g. due to propulsion of a wheelchair)
    • Ganglia arising from within the wrist
  • General mononeuritis
    • Leprosy
    • Vasculitis
    • Hereditary neuropathy
    • Acromegaly

Investigations

  • Nerve conduction studies to confirm diagnosis
  • Radiographs of wrist and elbow if underlying fracture suspected

Management

  • Multidisciplinary approach
  • Splinting, avoidance of exacerbating activities
  • Consider surgical decompression

Ulnar Nerve Palsy

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