Multifocal motor neuropathy: the first two cases

The author presents here the clinical history of 2 patients with chronic asymmetric motor neuropathy of the upper limbs. The affected muscles were weak but not wasted, and there were many fasciculations and myokymia. Electrophysiological examination recognised (i) proximal multifocal persistent conduction blocks located outside the usual entrapment sites, (ii) asynchronous and arrhythmic firing of a large number of fasciculation potentials recorded in the paretic muscles that were isolated or grouped, discharging distally on the blocked axons, and (iii) reduction of the number of motor unit potentials according to the severity of the conduction block during maximal voluntary contractions. During follow-up the weakness of these 2 patients slowly increased, and new conduction blocks could be seen at each examination, together with progressive denervation and amyotrophy. The patients died several years after onset, but no nerve biopsy was available. The patients were described in a medical thesis in 1986 and were the first two to be published and known to suffer from a peripheral neuropathy nowadays known as multifocal motor neuropathy. It is underlined that in 1986 the nosology of this neuropathy was unknown and there were neither biological markers nor treatment.