Electromyographic and nerve conduction findings in a patient with neuromyotonia, normocalcemic tetany and small-cell lung cancer.

A 57-year-old man with neuromyotonia and normocalcemic tetany as probable paraneoplastic symptoms of small-cell lung cancer was examined neurophysiologically. In EMG, spontaneous action potential generation was demonstrated in peripheral motor axons. There were also time-locked high-frequency discharges after some voluntarily activated motor unit potentials. After electrical stimulation of motor axons, the M-response as well as spinal F-response or H-reflex was often followed by a sequence of oscillating potentials which could last several hundred msec. There was no evident peripheral polyneuropathy. Tetany subsided when carbamazepine therapy was started. The only striking abnormality in extensive laboratory studies was an increase in the plasma noradrenaline value.