Background: Hemifacial Sapsm (HFS) is a common movement disorder in Thailand. Botulinum toxin type A
(BTA) is an effective and safe treatment for this condition. The success of BTA treatment depends on the experience of the clinician.
Objective: To study the demographic data, efficacy and safety of low dose BTA injection in HFS patients.
Setting: The Spastic and Dystonia Clinic, Department of Rehabilitation Medicine, King Chulalongkorn Memorial Hospital.
Design: Open-label, prospective case-series study.
Patients: All patients with HFS referred for BTA injection from December 1st, 1995 to November 30th, 2003.
Method: Sex, age, side of spasm, onset of symptoms before BTA injection, underlying diseases, sites of BTA
injection, dose of each BTA treatment, duration of response, efficacy, and side-effects were analyzed. 3-5 units of BOTOX were intramuscularly injected per site to all muscles that had spasm. After injection, a 20-minute cold compression on the first day was followed by 20-minute warm compression with massage at each injection site per day for 14 days.
Results: A total of 112 patients with HFS were treated with 874 BTA treatments. There were 71 females (63.4%) and 41 males (36.6%). The mean age was 45 years. 75 patients (67%) were affected on the left side. Mean duration of symptoms was 3.4 years. The sites of injection were orbicularis occuli and orbicularis oris muscles in all 874 treatments (100%). The mean dose of all treatments was 25 units. The mean initial dose was 30.5units.The mean dose for subsequent injection was 23 units. The mean duration between treatments was 4.7 months. The mean initial duration was 3.5 months. The mean duration for subsequent injection was 4.8 months. The outcomes of treatment assessed at 4 weeks after injection classified as excellent (> 80% improvement) were found in 845 treatments (96.7%). Most treatments had no complication (91.9%). Ptosis,
facial paresis and double vision were mild and transient, lasting 1-4 weeks. There were no long-term complications
of BTA treatment in the present series.
Conclusion: Low dose BTA injection is an effective treatment for hemifacial spasm patients. There was a
longer duration of response in subsequent injections and a lower complication rate in the present study when compared to others.

Keywords: Botulinum toxin, Hemifacial spasm