[Single fibre electromyography in 18 patients with amyotrophic lateral sclerosis]

Single fibre electromyography (SFEMG) is a method that complements conventional electromyography and studies the activity of individual muscle fibres and of the neuromuscular junction. AIMS. We attempt to demonstrate the presence of reinnervation disorders by studying Jitter, fibre density (FD) and the presence of neurogenic blocks in patients with amyotrophic lateral sclerosis (ALS).

SFEMG was carried out on 18 patients diagnosed with ALS. All the patients were submitted to a voluntary SFEMG in the extensor digitorum communis muscle of the fingers on the most affected side.

The SFEMG in the extensor digitorum communis muscle of the fingers showed alterations in 13 out of the 18 patients studied (72%). FD was the most reliable parameter for translation of the motor neuron instability and increased in all cases. This was followed by the mean and the maximum individual (62%) Jitter and, lastly, the percentage of blocks (38%).

In ALS, the parameters studied with SFEMG were modified in 72% of the cases studied. There is an overall correlation between the length of time the patient has had the disease and the modifications in the SFEMG (21.5 versus 13.7 months). The degree of clinical involvement is higher (6.5/13) in those who present an altered SFEMG compared to those who present a normal SFEMG (5.3/13).