Complications of botulinum toxin application: differences between hemifacial spasm and post-facial palsy synkinesis

Abstract

Dear Editor,Although hemifacial spasm (HFS) and post-facial palsysynkinesis (PFPS) are two different entities with differentunderlying causes, both share an effective treatment option:botulinum neurotoxin (BoNT). Its mechanism is temporaryblocking of the presynaptic release of acetylcholine inneuromuscular junction which lasts 3–6 months [1].Herein, we report the complications of BoNT use in HFSand PFPS.A retrospective analysis was conducted using themedical records of well documented 30 HFS and 20PFPS patients. Botilinum toxin A (Botox ) was recon-stituted with 2 ml of preservative free 0.9 % salinesolution to yield toxin in a concentration of 5 units per0.1 ml. Selected muscles were orbicularis oculi, corru-gator supercilii, frontalis in superior facial area, zygom-aticus, orbicularis oris, mentalis in middle and inferiorfacial area. Statistical analysis was performed usingMann–Whitney U test.Hemifacial spasm group consisted of 17 females and 3males with a mean age of 47 ± 11 years. The meanduration of symptoms was 17 ± 8 months. In threepatients a dolicho-ectatic basilar artery was founded on thesymptomatic side in brain magnetic resonance imaging. Allthe patients received 3–9 BoNT injections. Mean BoNTdose was 66 ± 56 U. Of HFS patients, 34 % developedcomplications: ptosis 24 % and orbicularis oris paralysis10 %.Post-facial palsy synkinesis group consisted of 18females and 2 males with a mean age of 59.3 ± 12 years.The mean duration of symptoms was 19 ± 8 months. Amedical history of Bell’s palsy was present in 12 patients.All of the patients received 3–7 BoNT injections. MeanBoNT dose was 53 ± 24 U. Complications occurred in77 % of PFPS patients consecutively: ptosis 33 %, dry eye-lagophthalmos 11 %, orbicularis oris paralysis 11 %, eyeand mouth complications together 22 %. The difference ofcomplication rates between the two groups was statisticallysignificant (p:0.04).Based on our results, it appears that complications ofBoNT are more frequent in PFPS. This may be due to theprevious muscle weakness and axonal damage in PFPS [2].In conclusion, choosing hyperactive muscle for injectionsand lower doses of BoNT in PFPS may reduce complica-tion ratios.