Botulinum toxin (BT) is the treatment of choice for hemifacial spasm (HFS). When BT is injected into the affected side, patients may experience increased facial asymmetry. We wanted to evaluate in a prospective, randomised, placebo-controlled study whether bilateral BT injections may reduce this facial asymmetry. For this, we treated 19 HFS patients with unilateral and 24 with bilateral BT therapy using CBTX-A (Lanzhou Biological Products Institute, Lanzhou, China). BT doses on the affected side were standard doses, on the non-affected side they were one-third of those. Facial asymmetry was studied with the Sunnybrook facial grading system (SFGS), the Facial Clinimetric Evaluation Scale (FaCE), the Symmetry Scale for Hemifacial Spasm (SSHS) and a self-assessment scale. As shown in SFGS and SSHS, bilateral BT therapy reduces facial asymmetry, whilst unilateral BT therapy increases it. Both effects are more pronounced during voluntary facial movements than at rest. BT effect delay, BT effect duration, adverse effect frequency and severity were not affected. FaCE total score, some of its subscores and the self-assessment scale did not show an effect. Bilateral BT therapy may improve the outcome of BT therapy for HFS without producing additional adverse effects. This strategy, however, raises drug costs (by about a third). Using even higher doses in the non-affected side may intensify the improvement even further. Future studies may also monitor the patient's quality of life and the naïve public's overall perception of the patient's facial expression.
Keywords: Botulinum toxin; Facial asymmetry; Hemifacial spasm; Therapy.