Axial myoclonus in paraproteinemic polyneuropathy.

We describe a patient with a paraproteinemic anti-myelin-associated glycoprotein (anti-MAG) antibody polyneuropathy and concomitant axial myoclonic jerks. Neurophysiological investigation revealed that axial jerks were asymmetrical and exaggerated by lying in bed. They disappeared during mental arousal and sleep. Analysis of axial myoclonus showed that the first activated muscle was the left rectus abdominis with subsequent rostral and caudal propagation of a propriospinal type. Plasmapheresis substantially reduced the frequency and intensity of axial myoclonic jerks. In our patient, propriospinal myoclonus was associated with anti-MAG polyneuropathy, but the causal relationship remains unclear.