Objective: To quantify the clinical changes in tremor during the different stages of thalamotomy, and to investigate the relationship between intraoperative findings and clinical outcome.

Background: Thalamotomy, involving radiofrequency (RF) ablation of the thalamic ventral intermediate nucleus (VIM), alleviates medication-refractory tremor in patients with movement disorders such as Parkinson’s Disease (PD), Essential tremor (ET) and Holmes tremor (HT). However, limited data is available on tremor intensity during different thalamotomy stages. Also, the predictive value of intraoperative tremor status for treatment outcome remains unclear.

Method: Data were gathered between January 2020 and May 2022 during consecutive unilateral VIM RF-thalamotomy procedures in patients with PD (n=11), ET (n=6) and HT (n=3). MDS-UPDRS scores and tri-axial accelerometry data were obtained during rest, postural, and intention tremor tests. Measurements were performed intraoperatively (1) before lesioning-probe insertion, (2) directly after lesioning-probe insertion, (3) during coagulation, (4) directly after coagulation, and (5) 4-6 months post-surgery. Accelerometric data were recorded continuously during the coagulation process. Outcome measures included MDS-UPDRS tremor scores and accelerometric parameters (peak-frequency, tremor amplitude, and area-under-the-curve of power (AUCP)). Tremor intensity was assessed for the insertion effect (1-2), during coagulation (3), post-coagulation effect (1-4), and postoperative effect (1-5).

Results: Following insertion and coagulation, tremor intensity improved significantly compared to baseline (p<0.001). The insertion effect clearly correlated with the postoperative effect (ρ=0.908, p<0.001). This was also the case for the post-coagulation effect (ρ=0.932, p<0.001). Both tremor amplitude and AUCP declined gradually during coagulation. Peak frequency did not change significantly intraoperatively. Accelerometric amplitude and AUCP both correlated significantly with MDS-UPDRS ratings (ρ≥0.688, p<0.001).

Conclusion: This study shows that both the post-insertion effect and the post-coagulation effect are good predictors for thalamotomy outcome. Accelerometric monitoring of tremor allows the objective quantification of these intraoperative parameters, reducing the dependency on experienced raters for reliable clinical assessments.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-added-value-of-accelerometric-monitoring-during-thalamotomy/