EMG showed neurogenic MUPs, profuse fibrillations, fasciculations, trains of discharges, and loss of motor units in the right abductor pollicis brevis (APB). Motor CB and temporal dispersion were present in the ulnar and median nerves at the axilla, whereas sensory conduction was normal. The US of the nerves at the axilla and brachial plexus was normal.

Repeated excitability testing of the median nerve at wrist over 3 years showed a progressive 80% decrease in fast potassium conductance (GKfN), 360% increase in inward rectification (GH), and 25% increase in Barrett-Barrett conductance (GBB).

MMN is considered a focal disorder. However, this study indicated widely distributed paranodal abnormalities and ion-channel dysfunction far distal to the site of CB that can be involved in spontaneous activity.

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