A 32-year-old woman reports variable ptosis that is worse in the evening. On examination she has bilateral ptosis with normal ocular motility today, but a photograph from six months ago shows ptosis on the opposite side. After holding an ice pack over the closed eyelids for two minutes, the ptosis measurably improves. The MOST appropriate next step is:

• A Tensilon (edrophonium) challenge test
• B Levator resection surgery
• C Orbital MRI with fat suppression
• D Serum acetylcholine receptor antibody assay ✓

Explanation

The history of variable, fatigable ptosis with shifting laterality and a positive ice pack test establishes myasthenia gravis. The ice pack test improves ptosis by enhancing neuromuscular transmission at cooler temperatures. Serological testing for acetylcholine receptor antibodies confirms the diagnosis non-invasively. Edrophonium testing is now rarely used due to cardiac arrhythmia risk and is reserved when serology is negative. Surgery is contraindicated before systemic evaluation because of perioperative respiratory crisis risk.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.