The Challenge of Choosing the Right Stimulation Target for Dystonic Tremor—A Series of Instructive Cases

Abstract

BackgroundThalamic deep brain stimulation (Th‐DBS) is established for medically refractory tremor syndromes and globus pallidus stimulation (GPi‐DBS) for medically refractory dystonia syndromes. For combined tremor and dystonia syndromes, the best target is unclear.ObjectivesWe present four patients with two different profiles whose clinical course demonstrates that our current analysis of clinical symptomatology is not a sufficient predictor of surgical success.MethodsOutcome parameters were assessed with observer‐blinded video ratings and included the Fahn‐Tolosa‐Marin‐Tremor Rating Scale (FTM‐TRS) and the Unified Dystonia Rating Scale (UDRS).ResultsTwo patients with ‘predominant lateralized action tremor’ of the hands and mild cervical dystonia showed no relevant tremor improvement after GPi‐DBS, but UDRS improved (mean: 45%). Rescue Vim‐DBS electrodes were implanted and both patients benefited significantly with a mean tremor reduction of 51%.Two other patients with ‘axial‐predominant action tremor of the trunk and head’ associated with cervical dystonia underwent bilateral Vim DBS implantation with little effect on tremor (24% reduction in mean FTM‐TRS total score) and no effect on dystonic symptoms. GPi rescue DBS was implanted and showed a significant effect on tremor (63% reduction in mean FTM‐TRS) and dystonia (49% reduction in UDRS).ConclusionsThe diagnosis of dystonic tremor alone is not a sufficient predictor to establish the differential indication of Gpi‐ or Vim‐DBS. Further criteria (e.g., proximal‐distal distribution of tremor/dystonia) are needed to avoid rescue surgery in the future. On the other hand, the course of our patients encourages rescue surgery in such severely disabled patients if the first target fails.This article is protected by copyright. All rights reserved.

Effect of Thalamic versus Pallidal Deep Brain Stimulation on Head Tremor in Dystonic and Essential Tremor Patients—A Retrospective Video‐Blinded Study

“…Recent evidence suggests that axial‐proximal dystonic tremor (ie, dystonic head or trunk tremor) may better respond to GPi‐DBS compared to Vim‐DBS, whereas distal dystonic tremor (ie, dystonic extremity tremor of the arms or legs) may well respond to Vim‐DBS. 20 , 21 Individual patient expectations need to be considered as well. For example, if the main complaint is caused by head tremor and dystonic symptoms subjectively play a minor role for the patient, this may have a decisive influence on the choice of the target point to achieve high patient satisfaction and an improvement in quality of life.…”