Trigeminal myokymia in a young girl.

Myokymia results from complex bursts of repetitive discharges of a motor unit typically attributable to a demyelinating condition. We report a 12-year-old girl with unilateral trigeminal myokymia who presented with involuntary jaw movements. Electromyography demonstrated unilateral rhythmic myokymic discharges in the left masseter and temporalis muscles at a rate of 3.5 Hz. Abnormal jaw movements spontaneously resolved over 8 months without treatment or residual deficits. The pathophysiology of myokymic discharges is discussed.