A 50-year-old woman with known myasthenia gravis on pyridostigmine 60 mg every 4 hours presents with worsening ptosis, dysphagia, and respiratory distress. Tensilon (edrophonium) test is performed: 2 mg IV is given as a test dose with no adverse reaction, followed by 8 mg IV. After 60 seconds, her ptosis and dysphagia markedly improve. This response indicates which of the following?
- A Cholinergic crisis requiring increased pyridostigmine
- B Myasthenic crisis requiring increased immunotherapy or plasmapheresis ✓
- C Lambert-Eaton syndrome misdiagnosed as myasthenia gravis
- D Seronegative myasthenia gravis with MuSK antibodies
Correct answer: B. Myasthenic crisis requiring increased immunotherapy or plasmapheresis
Explanation
A positive Tensilon test (improvement in muscle weakness after IV edrophonium) indicates myasthenic crisis, meaning insufficient acetylcholine at the neuromuscular junction due to the disease itself, not overmedication. In cholinergic crisis (too much pyridostigmine), weakness worsens or does not improve after edrophonium, and muscarinic side effects (fasciculations, miosis, secretions) are present. Myasthenic crisis management includes IVIG or plasmapheresis, not more pyridostigmine.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.