Question

A 35-year-old female has proximal weakness of muscles, ptosis and easy fatiguability. The best test to diagnose her condition is:

• A. Muscle biopsy
• B. CPK
• C. Edrophonium test
• D. EMG

Hint:

A drug that boosts acetylcholine briefly reverses ptosis and weakness.

Answer 1

The Correct Option is C

Step 1: The combination of fluctuating proximal weakness, ptosis and fatiguability that worsens with activity in a young woman is the classic picture of myasthenia gravis, a disorder of the neuromuscular junction.
Step 2: The edrophonium (Tensilon) test uses a short-acting acetylcholinesterase inhibitor that increases acetylcholine at the junction; in myasthenia gravis it produces a rapid, transient improvement in ptosis and weakness, making it a quick bedside diagnostic test. So option 3 is correct.
Step 3: Muscle biopsy (option 1) and CPK (option 2) are tests for primary muscle disease (myopathy) and are typically normal in myasthenia, since the defect is at the junction, not the muscle fibre.
Step 4: EMG, specifically repetitive nerve stimulation or single-fibre EMG, supports the diagnosis, but among the choices given the edrophonium test is the best/most specific immediate answer for this classic presentation.
Conclusion: The answer is option 3 (Edrophonium test).