Japan: Botulinum toxin injection into laryngeal muscles is safe and effective for the treatment of spasmodic dysphonia (SD), finds a recent study in the European Journal of Neurology.
Botulinum toxin injection is an accepted standard treatment for SD and this study provides additional data for safety and efficacy of this treatment, note the authors.
SD is a rare form of focal dystonia that occurs in the absence of phonatory organ paralysis or other structural pathology. It is characterized by involuntary intermittent spasms of the intrinsic laryngeal muscles. BT injection has been standard treatment for spasmodic dysphonia. However, only a few high‐quality clinical studies have appeared, and BT is used off‐label in most countries.
Masamitsu Hyodo, Kochi University, Nankoku, Japan, and colleagues performed a multicenter, placebo‐controlled, randomized, double‐blinded, parallel‐group comparison/open‐label clinical trial (the BOtulinum toxin Injection therapy for Spasmodic dySphonia [BOISS], study).
The study aimed at obtaining approval for BT therapy for SD in Japan. This is the first clinical trial based on Good Clinical Practice (GCP) guidelines to be conducted on BT worldwide.
The study enrolled twenty‐four patients (22 with adductor SD and two with abductor SD). The primary end point was the change in the number of aberrant morae (phonemes) at 4 weeks after drug injection.
Key findings of the study include:
In the adductor SD group, the number of aberrant morae at 4 weeks after injection was reduced by 7.0 ± 2.30 (mean ± SE) in the BT group and 0.2 ± 0.46 in the placebo group.
The improvement persisted for 12 weeks following BT injections.
The strain element in GRBAS scale significantly reduced at 2 weeks after BT treatment.
The VHI and VAS scores as subjective parameters also improved. In the abductor SD group, one patient responded to treatment.
Adverse events included breathy hoarseness (77.3%) and aspiration when drinking (40.9%) but were mild and resolved in 4 weeks.
"Botulinum toxin injection was safe and efficacious for the treatment of SD. Based on these results, BT injection therapy was approved as an SD treatment in Japan.," concluded the authors.
The study titled, "Botulinum toxin injection into the intrinsic laryngeal muscles to treat spasmodic dysphonia: A multicenter, placebo‐controlled, randomized, double‐blinded, parallel‐group comparison/open‐label clinical trial," is published in the European Journal of Neurology.
DOI: https://onlinelibrary.wiley.com/doi/10.1111/ene.14714