Fibrillation potentials and positive sharp waves in patients with antecedent paralytic poliomyelitis.

The diagnosis of post-polio syndrome depends not only on clinical signs, but on sophisticated laboratory tests such as histochemical muscle biopsy and immunohistochemical studies which are very expensive and not available in all laboratories. From eighty-eight previous poliomyelitis victims, muscles with grade 4 or lower strength were examined electromyographically for fibrillation potentials and positive sharp waves. There were no muscles with grade III or IV fibrillation potential and positive sharp waves, 8 with grade I (3.7%) and 7 with grade II (3.2%). Fibrillation potentials were more frequent in muscles with lower grade of strength. The minimum time interval between primary insult and the time of evaluation for patients who had sign of denervation was 36 months. This was 28 months for patients who had no sign of denervation. So we can conclude that denervation beyond this time in muscles with power greater than 3/5 is highly suggestive of a new process rather than primary insult in patients with new atrophy or fatigue.