Cortical myoclonus due to hypocalcemia 12 years after thyroidectomy

Although seizures have been described in hypocalcemia, myoclonus has been rarely reported. We report the first case of a patient with hypocalcemic cortical myoclonus due to hypoparathyroidism following a previous thyroidectomy. The patient was an 84-year-old woman who presented with multifocal myoclonus, which was predominant in the upper extremities, neck, jaw, and facial muscles. Electrophysiological studies revealed enlarged somatosensory evoked potentials, cortical reflexes evoked by peripheral nerve stimulation, and a cerebral potential preceding myoclonic jerks determined by jerk-locked averaging. All these findings were consistent with cortical myoclonus. The myoclonic state disappeared as serum calcium level became normal. Hypocalcemia should be considered in patients who had had a thyroidectomy, even if it was performed more than 10 years previously.