Miraan Jhaveri, Mary Hawkshaw, Robert T Sataloff
DBS, particularly in the Ventral Intermediate (VIM) nucleus, is associated with voice improvement in patients with LD refractory to BTX-A. The evidence base is limited in design as it remains case-level due to lack of robust prospective trials. Prospective, multicenter studies and randomized controlled trials are needed to establish durability and efficacy of DBS.
OBJECTIVES: Laryngeal dystonia (LD) is a focal dystonia causing involuntary laryngeal muscle contractions that can impair voice. Botulinum toxin type-A (BTX-A) injection is the current standard of care; however, a subset of patients experience treatment failure due to neutralizing antibody development or other reasons. Deep brain stimulation (DBS) has emerged as a potential alternative. This systematic review and descriptive pooled analysis aimed to synthesize all available evidence on the efficacy of DBS for LD.
METHODS: A systematic search of MEDLINE, Web of Science, Scopus, and Google Scholar was conducted in accordance with the PRISMA 2020 guidelines (PROSPERO: CRD420251105305). Studies were eligible if they enrolled adult patients with LD who underwent DBS and reported at least one voice outcome. Given the predominant amount of heterogeneity present in the case reports, outcomes were synthesized descriptively as absolute changes and percentage improvements from baseline.
RESULTS: Ten studies, including two randomized controlled trials, two case series, and six case reports published between 2009 and 2024, were included, comprising 24 patients (mean age 66.0 years). The predominant subtype was adductor LD (n = 21), and most patients received ventral intermediate nucleus (VIM) DBS (n = 22). Mean percentage improvement on the Unified Spasmodic Dysphonia Rating Scale (USDRS) was 47.6%, and 9 of 10 patients met the prespecified threshold for clinical response on the USDRS. Mean improvement on the Voice Handicap Index (VHI) was 49.5%, and improvement on the Voice-Related Quality of Life scale (VR-QOL) exceeded 74%. Where calculable, Cohen's d was -2.25, indicating a large treatment effect.
CONCLUSION: DBS, particularly in the Ventral Intermediate (VIM) nucleus, is associated with voice improvement in patients with LD refractory to BTX-A. The evidence base is limited in design as it remains case-level due to lack of robust prospective trials. Prospective, multicenter studies and randomized controlled trials are needed to establish durability and efficacy of DBS.