# Rebound Tremor Frequency as a Potential Diagnostic Marker for Delayed Therapy Escape after Thalamic Deep Brain Stimulation for Essential Tremor—Insights from a Cross-Sectional Study

## TL;DR

This study explores if a specific rebound tremor after turning off brain stimulation can help identify patients with reduced treatment effectiveness for essential tremor.

## Contribution

The study introduces low-frequency rebound tremor as a potential diagnostic marker for delayed therapy escape after deep brain stimulation.

## Key findings

- A low-frequency rebound tremor in the left hand after stimulation OFF is a potential marker for delayed therapy escape.
- Receiver operating characteristic analysis showed an area under the curve of 0.86 for identifying DTE using rebound tremor.

## Abstract

Delayed therapy escape (DTE) is frequent after thalamic deep brain stimulation for essential tremor, leading to reduced quality of life, often with ataxic symptoms, and early recognition is challenging. Our goal was to examine whether a low-frequency rebound tremor of the left hand after switching off stimulation is useful as a diagnostic marker for DTE. In this cross-sectional study with additional retrospective analysis, we examined 31 patients with bilateral thalamic DBS ≥ 12 months for essential tremor, using quantitative assessments including video-based motion capture, Fahn–Tolosa–Marin Tremor Rating Scale (FTMTRS), and scale for the assessment and rating of ataxia (SARA). If available, preoperative (preOP) and 12-month postoperative assessments were included in the analysis. Evaluations occurred with DBS activated (ON) and deactivated (OFF). A higher ratio FTMTRS nowON/preOP indicated DTE. Preoperative FTMTRS scores were available for 16 patients, including 5 patients with DTE. The receiver operating characteristic analysis found an area under the curve of 0.86 (p = 0.024) for identification of DTE by low-frequency rebound tremor (i.e., OFF) on the left. In conclusion, it could serve as a potential diagnostic marker.