Comparative efficacy of PSA and VIM deep brain stimulation in essential tremor: a network and multilevel...

Essential tremor (ET) is a common movement disorder often treated with deep brain stimulation (DBS) when medications fail. While the ventral intermediate nucleus (VIM) is the traditional DBS target, newer studies suggest that the posterior subthalamic area may be a more suitable target with a comparable safety profile. Nevertheless, previous studies have failed to reach a consensus regarding the superiority of PSA. Studies comparing VIM and PSA/ZI DBS in ET patients were identified through PubMed, Web of Science, and Scopus databases. Primary outcomes included changes in Fahn Tolosa Marin total tremor scores, with secondary outcomes covering action/intention, postural, and head tremor subscores, quality of life measures, depression status, and adverse events between the targets. 52 studies were included. Both VIM and PSA DBS provided marked and clinically significant tremor reduction (mean difference - 28.24 vs. - 31.23). The 3-point difference between targets was statistically nonsignificant (p = 0.428) and clinically negligible, confirming comparable efficacy. Efficacy for both targets declined over time (~ 1.2 points/year) resulting in the loss of almost half the initial efficacy within 10 years. PSA DBS was significantly superior for head tremor (68% greater improvement over VIM) and was associated with a lower risk of dysarthria. Depression score improved marginally with VIM DBS, while cognitive outcomes remained largely unchanged. Bilateral implantation offered no significant advantage over unilateral DBS. Quality of life and functional improvements were comparable, though PSA showed a trend toward greater QoL gains (p = 0.060). VIM and PSA DBS offer comparable tremor reduction and functional benefits, with PSA showing advantages for head tremor and fewer speech-related side effects. Declining efficacy over time and minor cognitive effects underline the importance of long-term monitoring. Standardized protocols and tractography-guided targeting are needed to optimize outcomes.Clinical trial number: not applicable.