[Analysis of the interference pattern in patients with muscular dystrophy]

The conventional electromyography contribute to differentiation of myopatic and neuropatic patterns in neuromuscular disorders, however, the classical patterns related to myopatic changes can result in neurogenic components, this confusion could be due to denervation and reinervation changes involved at the different stages of those diseases.

Demonstrate the importance of quantitative electromyographic techniques, as the interference pattern analysis (IPA), for a better differentiation of muscular dystrophies.

IPA was done in 95 patients with 3 different muscular dystrophies: 52 Duchenne muscular dystrophy (DMD), 33 limb girdle muscular dystrophy (LGMD) and 10 myotonic muscular dystrophy (MD) individuals and in a control group of 25 individuals. The left braquial biceps and right anterior tibial muscles were evaluated; the variables analyzed were turns/seconds (t/s), amplitude/turns (a/t), ratio turns/amplitude mean and root squared mean (RSM).

We found statistical significant differences in all variables in both braquial biceps and right anterior tibial muscles (p < 0.05) in DMD patients. In LGMD we only found differences in a/t in braquial biceps. In MD the differences were observed in a/t, ratio and RSM in braquial biceps, and in a/t (in anterior tibial).

All the DMD patients show differences in IPA values in relation to control group, MD only in biceps, However there were not important changes in LGMD probably because the diversity and lack of homogeneity in affected muscles in this group.