Fig 1.
Study flow diagram.
Table 1.
Summary of inclusion criteria for eligible studies.
Fig 2.
Distribution of DBS groups against the control groups.
Fig 3.
Distribution of study categories.
Fig 4.
ROB2 tool for bias assessments in RCTs-prospective interventional study (*)-cross over designs (†).
Fig 5.
Bias risk assessment in studies utilizing a within-subject experimental design.
Fig 6.
NOS assessment of comparative observational† and cohort studies.
Fig 7.
Forest plot depicting the analysis of verbal fluency in PD and ET patients over follow-ups.
The weight percentage of each study is listed alongside the effect estimate. Substantial heterogeneity is observed (I2: 62.40%, 95% CI).
Fig 8.
Forest plot analysis examining verbal fluency following DBS (A) This subplot compares different targets (STN vs GPi) in PD patients, showing no heterogeneity (I2: 0.00%, 95% CI). (B) This subplot explores ON versus OFF stimulation status in PD and ET patients (while consistently on medication), indicating minor heterogeneity (I2: 19.6%, 95% CI). Each study’s weight percentage is presented alongside the effect estimate.
Fig 9.
Forest plots examining articulation and phonation and word production in PD patients following DBS (A) Articulation and Phonation (F0) in PD patients, revealing moderate heterogeneity (I2: 45.50%, 95% CI) in the comparison of ON versus OFF status; (B) Word production over post-surgery follow-ups—no heterogeneity was observed (I2: 0.00%, 95% CI). Each study’s weight percentage is presented alongside the effect estimate.