Median Nerve Palsy

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

Nerve supply

  • Motor
    • Anterior forearm compartment
      • Superficial
        • Pronator teres
        • Flexor carpi radialis
        • Palmaris longus
        • Flexor digitorum superficialis (proximal interphalangeal joint flexion)
      • Deep
        • Flexor pollicis longus
        • Pronator quadratus
        • Medial half of flexor digitorum profundus (distal interphalangeal joint flexion)
    • Hand
      • Lateral two lumbricals
      • Opponens pollicis
      • Abductor pollicis brevis
      • Flexor pollicis brevis
  • Sensory
    • Palmar aspect of lateral three and a half digits
    • Palmar sensation (palmar cutaneous branch, proximal to wrist crease – not in carpal tunnel)

Physical signs

  • Inspection
    • Wasting of the thenar eminence
    • Hand of benediction (if injured at the elbow, seen when asked to make a fist) – paralysis of FDS, lateral FDP and the lateral two lumbricals
  • Power
    • Opponens pollicis
      • “Make an OK sign”
    • Flexor pollicis
      • “Push up against my thumb”
    • Abductor pollicis
      • “Push in against my thumb”
    • Lateral two lumbricals (flexion MCPJs and extension of IPJs)
  • Sensation
    • Numbness over lateral three and a half digits
    • Palm affected in lesions proximal to the wrist
  • Other tests
    • Tinnel’s test (percussion of the wrist distal to the wrist crease with the wrist extended) – tingling

Causes

  • Compression neuropathy
    • Carpal tunnel syndrome (sparing of thenar sensation) – see “Approach to Hand Pain”
    • Pronator teres syndrome
    • Anterior interosseous neuropathy (rare, only motor components, particularly opponens pollicis)
  • Trauma
    • Supracondylar humeral fracture
  • Vasculitis (mononeuritis), e.g. ANCA-associated vasculitides
  • Infections (HSV, Lyme disease)

 Investigations

  • Nerve conduction studies to confirm diagnosis and assess severity
  • Consider EMG of thenar eminence
    • Electrically silent
    • Recent denervation: fibrillation potentials
  • Consider full blood count (anaemia of chronic disease)
  • Renal function (secondary CTS)
  • Fasting plasma glucose, HbA1c (secondary CTS)
  • Consider autoimmune profile
    • Anti-nuclear antibody
    • Rheumatoid factor, anti-cyclic citrullinated peptide (RA, secondary CTS)
    • Anti-neutrophil cytoplasmic antibody
    • Extractible nuclear antigens
  • Consider anterior pituitary hormone screen
    • Insulin-like growth factor 1 (acromegaly, secondary CTS)
    • Thyroid function tests (hypothyroidism, secondary CTS)
  • Consider Borrelia burgdoferi serology if Lyme disease suspected

Management

  • Multidisciplinary team approach
  • Physiotherapy and occupational therapy to regain function
    • Wrist splinting in 30° extension
  • Local steroid injections
  • Carpal tunnel release surgery

Median Nerve Palsy

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