Stimulated single fiber EMG of the frontalis muscle in the diagnosis of ocular myasthenia.
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.
Valls-Canals
J
J
Unitat de Neuromuscular i Electromiografia, Institut Universitari Dexeus, C./Calatrava 83, 6(a) planta, 08017 Barcelona, Spain. unmemg@comb.es
Montero
J
J
Pradas
J
J
D000328:Adult; D000368:Aged; D001369:Axons / Q000502:physiology; D001763:Blepharoptosis / Q000209:etiology / Q000503:physiopathology; D002800:Cholinesterase Inhibitors; D004172:Diplopia / Q000209:etiology / Q000503:physiopathology; D004576:Electromyography / Q000379:methods*; D005152:Facial Muscles / Q000294:innervation / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology*; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology; D009388:Neostigmine; D009886:Ophthalmoplegia / Q000209:etiology / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002800:Cholinesterase Inhibitors; D009388:Neostigmine