Editors' Note: Comparison of Ice Pack Test and Single-Fiber EMG Diagnostic Accuracy in Patients Referred for Myasthenic Ptosis

In “Comparison of Ice Pack Test and Single-Fiber EMG Diagnostic Accuracy in Patients Referred for Myasthenic Ptosis,” Giannoccaro et al. compared the diagnostic accuracy of the ice pack test (IPT) with single-fiber EMG (SF-EMG) on the orbicularis oculi muscle in 155 patients, with ptosis being evaluated for ocular myasthenia defined as a positive response to the edrophonium test, presence of acetylcholine-receptor antibodies, a decrement of >10% of the third to fifth compound muscle action potential after repetitive nerve stimulation, or unequivocal response to oral steroids or acetylcholinesterase inhibitors for at least 3 months. They found that the IPT and SF-EMG had similar diagnostic accuracy in this patient population. Silvestri noted interest that (1) the IPT, a simple and cheap bedside assessment, is comparable with a complicated test like the SF-EMG; (2) the results of the IPT and SF-EMG were discordant for 10% of subjects (mostly in the setting of mild or isolated ptosis); and (3) the utility of the IPT was not evaluated in patients with isolated diplopia. Giannoccaro and Liguori responded that the discordance in results generally occurred in the setting of a negative IPT, which may be related to the lack of repetition of the test. They also cited previously published data that the IPT is useful in patients with isolated diplopia, particularly because SF-EMG may be negative in these patients.

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