An ice test for the diagnosis of myasthenia gravis.

Abstract

To determine whether ice application to a ptotic eyelid can differentiate myasthenic from nonmyasthenic ptosis. Prospective, multicenter, nonrandomized, comparative trial. 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. Palpebral fissures were measured before and immediately after a 2-minute application of ice to the ptotic eyelid. 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. 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. 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.