Evaluation of neostigmine test in diagnosis of myasthenia gravis initiated from extrocular muscles

Objective To investigate the usage of neostigmine test in diagnosis of myasthenia gravis (MG) initiated from extraocular muscles, including test methods and data analysis. Methods The clinical features of 100 consecutive patients with myasthenia gravis initiated from extraocular muscles were collected retrospectivelly, including initial symptom, number and department of visiting, evolution of symptoms and signs, methods and the judgment of therapeutic response for neostigmine test. Results (1) All patients with MG started from ptosis unilateral or bilateral or diplopia, among which 46%（46/100）of patients with both ptosis and diplopia. Within 21%（21/100） of patients, other muscles had been involved except for extrocular muscles before neostigmine test. Seventy-eight percent patients first consulted ophthalmology after (0.7±0.3) month from onset. It took (1.6±1.3) months for patients to visit neurologist for the first time. The average time for confirming diagnosis was (3.3±2.1) months.（2）After (2.0±1.5) times consulted at neurology department and (2.0±1.8) months after symptoms onset, the patients undergone neostigmine test. Positive reaction rate showed lower in low dosage group（60.9%(14/23) vs 98.3%(58/59),χ2=18.30，P<0.01）. Positive rate also showed lower in oral-take pyridostigmine bromide tablets group than neostigmine methylsulfate injection group（15/18 vs 98.3%(58/59)， χ2=4.428，P=0.035）.（3）Sixty-five percent patients had mild to moderate side effects after neostigmine injection, which disappeared in 60—120 minutes. Conclusions Non-standard operations of neostigmine test reduced the effectiveness of its diagnosis for MG initiated from extraocular muscles.Neurologist should attach importance totake standard neostigmine test to identify MG as soon as possible. Key words: Myasthenia gravis; Ophthalmoplegia; Neostigmine