Botulinum toxin in peripheral facial paralysis: systematic review and rehabilitation perspectives.
Silvia Domínguez Ibáñez
Across 13 studies of 1,821 patients, botulinum toxin injections consistently reduced facial synkinesis, eased muscle tightness, and improved symmetry and quality of life, with only mild, temporary side effects.
Evidence is strongest for the chronic phase.
Key findings
1All thirteen included studies reported improvements in facial symmetry, reduction of synkinesis, and better quality of life after BTX-A treatment.
2SAQ scores decreased significantly across multiple studies: from 46.2 to 37.6 (P=0.001), from 26.6 to 17.9 (P<0.05), and by 14.2 points (P<0.001), reflecting reduced synkinesis severity.
3BTX-A was generally well tolerated; adverse events were mild, transient, and dose-dependent, most often temporary muscle weakness, ptosis, mild dry eye, or lip asymmetry. No systemic complications or long-term adverse effects were observed.
Still to come
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What it does not show
Twelve of the 13 included studies are observational; the single RCT was rated as having some concerns for risk of bias, so the evidence base lacks a high-quality randomised trial. No meta-analysis was possible because of heterogeneity in study design, dosing protocols, injection sites, and outcome measures, so the 'consistency' of findings is narrative rather than statistical. The review protocol was not prospectively registered in PROSPERO, reducing transparency of the search and selection process. Most studies report short-term outcomes; long-term durability and the effect of repeated cycles over years remain uncertain. Most evidence pertains to the chronic sequelae phase; whether early BTX-A during partial recovery helps or hinders is still debated, and one study found early contralateral injection beneficial while others caution against it. A single author performed all quality assessments and data extraction, with no independent second reviewer. Dosing, timing, and muscle selection varied widely across studies, making it difficult to identify a single optimal protocol.
Declared interests
The author declares no conflict of interest with any financial organisation and states that no external funding was received for the study.
The easy way to misread this
Do not read the consistent positive narrative as proof that BTX-A is a proven, standardised treatment — 12 of the 13 included studies are observational, the one RCT had some concerns for bias, no meta-analysis was possible, and dosing, timing, and muscle targets varied so widely across studies that no single protocol is supported. The review is a synthesis of heterogeneous, mostly small studies, not a demonstration of efficacy in a controlled trial.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →