An ice test for the diagnosis of myasthenia gravis.

OBJECTIVE: To determine whether ice application to a ptotic eyelid can differentiate myasthenic from nonmyasthenic ptosis.

DESIGN: Prospective, multicenter, nonrandomized, comparative trial.

PARTICIPANTS: Twenty patients with myasthenia gravis (MG) and ptosis were evaluated in the neuro-ophthalmology service. CONTROL SUBJECTS: Twenty patients with nonmyasthenic ptosis evaluated in the same locale.

METHODS: Palpebral fissures were measured before and immediately after a 2-minute application of ice to the ptotic eyelid.

MAIN OUTCOME MEASURES: The difference in palpebral fissures in millimeters before and after ice application. Two or more millimeters of improvement after ice application was considered a positive ice test result.

RESULTS: A positive ice test result was noted in 16 of the 20 (80%) patients with MG and in none of the 20 patients without MG (P < 0.001). Of the 4 patients with MG and complete ptosis, 3 had a negative ice test result.

CONCLUSIONS: The ice test is a simple, short, specific, and relatively sensitive test for the diagnosis of myasthenic ptosis. The sensitivity of the ice test in patients with complete ptosis decreases considerably.