II. Pathophysiology

  1. Nitrous Oxide inhalation interferes with Vitamin B12 Metabolism
  2. Longterm abuse results in Vitamin B12 Deficiency
    1. Long segmental changes involving the Posterior Columns

III. Signs

  1. Progressive ascending Polyneuropathy (especially sensory)
  2. Distal extremity Paresthesias (starting with legs, ultimately involving arms)
  3. Lower extremity weakness or Incoordination (ultimately involving arms)
  4. Ataxia
  5. Lower extremity Deep Tendon Reflexes diminished or lost
    1. Positive Babinski Reflex

IV. Differential Diagnosis

V. Labs

  1. Macrocytic Anemia
  2. Decreased Serum Vitamin B12

VI. Management

  1. Vitamin B12 Replacement with 1000 mcg orally daily

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