Objective: To compare the effect of deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) in patients with Essential Tremor (ET) and ET-plus (ET-p).

Background: Following the recent consensus statement for the diagnosis of ET, a tremor syndrome with additional symptoms besides the typical action tremor (i.e. ataxia, rigidity or rest tremor) is now classified as ET-p [1]. However the therapeutic consequences of this new classification, especially regarding the effect of VIM-DBS as an effective treatment for medication-refractory ET [2], remains to be explored. Therefore, we retrospectively compared the effect of VIM-DBS in ET and ET-p patients.

Method: Patients diagnosed with ET prior to VIM-DBS, were reclassified as ET or ET-p according to the new diagnosis criteria, based on the patient file and, if available, preoperative video documentation. Tremor rating scale total scores (TRS) were retrospectively assessed in stimulation OFF and ON state using postoperative video documentation. As Shapiro-Wilk test showed normal distribution for TRS scores, TRS change scores were analyzed per group using paired t-tests and relative TRS change scores were compared in between groups with the two-sample t-test. Differences in variance of the relative TRS improvement were investigated using the two sample F-Test (all p≤0.05; reported as mean).

Results: 19 ET patients with VIM-DBS were retrospectively reclassified in ET (N=7) and ET-p patients (N=12). TRS in stimulation OFF did not differ between groups (ET: 37.29 (±22.07), ET-p: 32.92 (±14.95); p=0.612) and improved in both groups in stimulation ON (ET: 11.14 (±6.94), p=0.014; ET-p: 12.92 (±9.99); p<0.001). No significant difference in relative TRS improvement was observed between both groups (ET: 66.69% (±23.41); ET-p: 59.29% (±22.90); p=0.538). Although the variance did not differ significantly between both groups (p=0.89) the proportion of patients experiencing less than 60% TRS improvement was much higher in ET-p (ET: 14.3%, ET-p: 50%).

Conclusion: Although ET-p and ET patients profit similarly from VIM-DBS, outcome in ET-p patients seems more heterogenous. Further studies are needed to investigate differences in Et-p patients.

References: [1] Bhatia KP, Bain P, Bajaj N, et al. Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord;33:75–87. doi:10.1002/mds.27121 [2] Flora ED, Perera CL, Cameron AL, et al. Deep brain stimulation for essential tremor: a systematic review. Mov Disord Off J Mov Disord Soc 2010;25:1550–9. doi:10.1002/mds.23195

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-vim-dbs-in-et-plus-patients-as-effective-as-in-et-patients/