Stimulated single fiber EMG of the frontalis muscle in the diagnosis of ocular myasthenia

✍ Scribed by J. Valls-Canals; J. Montero; J. Pradas

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 127 KB
• Volume: 23
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/(sici)1097-4598(200005)23:5<779::aid-mus16>3.0.co;2-z

✦ Synopsis

We performed single fiber electromyography by axonal stimulation (SFEMG-AS) of the frontalis muscle of 16 patients with ocular myasthenia gravis (OM) and 33 controls. In the controls, values of mean consecutive differences (MCD) ranged from 5 to 55 micros (average, 14.7 +/- 2.8 micros) and mean MCD of individual MPs was 14. 6 +/- 6.8 micros. All the OM patients showed abnormal SFEMG-AS jitter before prostigmine was administered (mean MCD: 49.19 +/- 21. 82 micros, percentage of blocks: 20.97 +/- 18.53). Twenty or 30 min after prostigmine had been administered, we saw a significant improvement in jitter: mean MCD was 36.38 +/- 22.49 micros (P = 0. 005), and percentage of blocks was 10.16 +/- 18.87 (P = 0.008). The method was well tolerated. We conclude that SFEMG-AS of the frontalis muscle is a sensitive technique for the diagnosis of OM and is easy to carry out.