How is myasthenia gravis diagnosed?

• A. MRI brain
• B. Physical exam, serology antibodies, EMG, nerve testing
• C. Urinalysis
• D. Abdominal ultrasound

Answer: (B)

Diagnosis of myasthenia gravis rests on recognizing fatigable weakness and then confirming it with tests that assess neuromuscular transmission. The strongest approach is a combination of a thorough physical exam showing patterns like ptosis and diplopia that worsen with activity, plus objective testing: serology for acetylcholine receptor antibodies (and MuSK antibodies if needed), and electrodiagnostic studies such as repetitive nerve stimulation or single-fiber EMG that reveal impaired transmission at the neuromuscular junction. The Tensilon (edrophonium) test or an ice-pack test can support the diagnosis in some settings, but antibody and EMG testing provide more definitive confirmation. By contrast, imaging of the brain is not diagnostic for MG, and studies like urinalysis or abdominal ultrasound don’t inform the diagnosis.