Subdinical impairment of neuromuscular transmission in transient global amnesia

Objective: To investigate the neuromuscular transmission (NMT) of the patients with transient global amnesia (TGA) using single fiber electromyography (SFEMG). Background: The pathophysiology of TGA remains unknown and several elements support the hypothesis of a shared background with migraine. Recent studies showed that some migraineurs have subclinical abnormalities of NMT by using SFEMG. We aimed to test the patients with TGA using SFEMG. Methods: We investigated 6 patients diagnosed with TGA according to published criteria and 5 healthy volunteers with similar ages. SFEMG during voluntary contraction of the extensor digitorum communis muscle, nerve conduction studies and concentric needle electromyography were performed and 20 single fiber potential pairs were recorded from each subject and individual and mean jitter values were calculated. Results: Three patients with TGA showed pronounced NMT failure by SFEMG, whereas none of the controls disclosed this abnormality. The mean jitter value of TGA patients (35 33) was greater than that of the control subjects (25 15) (P = 0.006). Seventeen of the 120 individual jitter values of the TGA group and only 3 (from 3 different volunteers) of the 100 individual jitter values of the control group exceeded upper normal limit (P = 0.004). Conclusions: These results suggest that TGA shares the same type of subclinical abnormality of NMT observed in migraine patients in recent studies.