Ultrastructure of the syndrome of continuous muscle fibre activity.

The ultrastructure of muscle and the myoneural junction of a man of 60 suffering from the syndrome of continuous muscle fibre activity was studied. This syndrome is manifested by disturbances of walking, muscle weakness, permanent muscle contractions and involuntary movements. The myoneural junction was hypertrophied and showed ramifications of the secondary clefts. The presynaptic nerve ending contained no synaptic vesicles. The relationship of these findings to the disease is discussed.