Successful Treatment of Postauricular Muscle Myokymia Using Low-Dose Botulinum Toxin Type A

Postauricular muscle myokymia is a rare focal movement disorder caused by involuntary activation of the posterior auricular muscle.We report a 44-year-old woman with a 2-year history of intermittent bursts of rapid, irregular twitching localized to the right postauricular region, which aggravated when lying on her right side or turning her head rightward.Oxcarbazepine was ineffective.In a single injection session, botulinum toxin type A (Nabota, 10 U in 0.2 mL; 50 U/mL) was administered into the posterior auricular muscle.Given the small size and superficial location of the muscle, a concentrated, low-volume formulation was chosen to confine the toxin to the target area.Symptoms markedly improved within 3 days and resolved completely by day 5. Visual Analogue Scale decreased from 5 to 0 at 2 weeks, remained 0 at 3 months, and was 1 at 6 months without requiring further treatment.No adverse effects occurred.This case illustrates that the botulinum toxin type A can be a safe and effective option for focal postauricular muscle myokymia when the symptomatic muscle is accurately identified.