Voluntary multiplet discharge after the activation test for spasmophilia as an electromyographic sign of a mild form of this disease.

The electromyographic (EMG) diagnosis of spasmophilia is based on the appearance in a susceptible muscle of spontaneous burst (multiplet) discharges after an activation procedure consisting usually in 10 minutes ischemia followed by a pause of a length that varies with the author but does not exceed 5 minutes, and finally by a hyperventilation, again not exceeding 5 minutes. In investigations carried out many years ago we observed that a number of subjects with symptoms of spasmophilia showed no postischemic spontaneous bursts, but responded with bursts to voluntary contraction. In this work we present some findings leading to the conclusion that voluntary burst discharge after the activation procedure can represent a sign of spasmophilia and not a mere manifestation within normal limits. Thus, in most cases with no symptoms of spasmophilia, voluntary burst response was absent. On the other hand, most subjects with such an EMG alteration suffered of troubles attributable to spasmophilia. Crisis of tetania with partial or generalized contracture could be encountered in such cases with a frequency close to that of cases with mild spontaneous burst discharge, being, on the contrary, exceptional in cases with normal EMG. In a previous work we showed the existence of a close correlation between the increase above normal of the incidence of ischemic discharge and the intensity of postischemic spontaneous burst (multiplet) discharge. A significant increase of ischemic discharge was also found for the cases showing only voluntary bursts (34.29% of 487 cases as compared to 14.28% of 602 normals). In addition, the period of abnormal burst responses of motor units to voluntary command was significantly prolonged for the cases with more intense ischemic discharge. Finally, there is no gap between spontaneous and voluntary burst discharge, since not rarely a short contraction could trigger a rhythmical selfmaintained burst discharge entirely similar to the spontaneously occurring one. One may conclude that voluntary burst discharges, if rather persistent, can represent a sign of spasmophilic alteration of excitability that must be always tested EMG in suspected cases that give no spontaneous burst discharge to the facilitation procedures. It represents a change in excitability less severe than the spontaneous burst discharge.