Median Nerve Injury at wrist, a clinical diagnosis

EMG correlate: Median neuropathy at the wrist

Common cause

• Occupational injury → repetitive use
• Systemic causes
  • Diabetes Mellitus
  • Hypothyroidism ↓
  • Thiamine B1 Deficiency
• Edema at the wrist (also systemic)
  • SARD
    • RA - Rheumatoid Arthritis
  • Pregnancy → Temporary
    • typically in the 2ed or 3rd trimester,

Presentation

DDx

“Bilateral CTS” → indicate more systemic etiology

• Etiology listed above except occupational injury

vs. C6 Injury

• Sensory
  • No palm (thumb extension), forearm, or arm parasthesia
• Motor
  • No forarm or arm weakness
    • Pronation
    • Supination
    • Elbow flexion
  • Intrinsic hand weakness (C8-T1)
    • Thenar eminance weakness
    • 1st and 2ed lumbercle
• Reflex
  • No Bicep Tendon Reflex

Investigation

• EMG/NCS (NCS) → Confirm the diagnosis (necessary if need surgery)
  • Grade as mild, moderate, severe
    • NCS: Prolonged sensory and motor conduction can be diagnostic of CTS
    • EMG: not usually conducted for CTS, exception: prolonged latency → Abductor Pollicus Brevis (but very painful)
• US: visualize swelling at wrist
  • not a reliable test due to interpreter difference - need to collaborate with other findings, esp. EMG
• “Bilateral CTS” → Screening for the systemic etiology
  • HbA1c (< 6.5) → For DM
  • TSH (< 5) → For Hypothyroidism ↓
  • B12 → Vitamin B12 (Cobalamin) Deficiency

Treatment