In electromyography (EMG) the presence of fibrillation potentials or positive sharp-waves is often interpreted as a sign of acute ongoing denervation activity (DA). Large motor unit potentials and discrete interference pattern with large amplitude may indicate more chronic changes. Our hypothesis was that the proportion between acute and chronic EMG changes may be related to the disease course in amyotrophic lateral sclerosis (ALS).
Methods
Fifty-five consecutively patients referred for motor neuron disease at our department were included. Diagnosis according to the revised El Escorial criteria was confirmed during the course of the disease. Acute and chronic EMG changes in individual muscles were dichotomised and related to survival time after EMG by means of Kaplan-Meier statistics.
Results
For the anterior tibial muscle survival was shorter in patients with DA ⩾ 7/10 sites (log-rank test p < .01). For the abductor digiti minimi muscle the 11/2 year survival was only 25% in patients with DA ⩾ 7/10 sites compared with 76% in patients with less DA. No relations between DA in proximal muscles or chronic changes in limb muscles were found.
Conclusion
The amount of DA in distal limb muscles relates to survival in ALS.
Key message
EMG findings may predict prognosis in ALS.
