(BMJ)—A man in his 50s w/ hx of HTN presented w/ L eyelid drooping and difficulty swallowing. The ptosis was absent on waking and worsened during the day. Exam: bilateral ptosis L>R; otherwise unremarkable exam. Ptosis resolved w/ application of an ice pack. What is the dx?
Oculopharyngeal muscular dystrophy
Horner syndrome
Levator aponeurosis dehiscence
Myasthenia gravis
Ischemic stroke
You are correct. The ice pack test is positive in most pts w/ myasthenia gravis (MG), and this pt’s dx was confirmed by anti-AChR antibodies. The ice pack test has a specificity of 88% to 100%, implying that 0% to 12% of pts w/ nonmyasthenic ptosis will have a positive result. In MG w/ ocular manifestations, cooling is believed to reduce acetylcholinesterase activity by making more acetylcholine available at the neuromuscular junction, thereby reversing the ptosis (in nonmyasthenic ptosis, there is no acetylcholine deficiency at the neuromuscular junction).

Causes of unilateral nonmyasthenic ptosis include Horner syndrome, oculomotor nerve palsy, and levator aponeurosis dehiscence. Causes of bilateral nonmyasthenic ptosis include myotonic dystrophy and oculopharyngeal muscular dystrophy.

This pt developed difficulty chewing, dysphagia for food and saliva, dysarthria, fatigue, and generalized proximal weakness 2wk after initial presentation. He was successfully treated w/ pyridostigmine and prednisolone.

BMJ 2020;369:m1147