Distance between Active Electrode Contacts and Dentatorubrothalamic Tract in Patients with Habituation of Stimulation Effect of Deep Brain Stimulation in Essential Tremor

Abstract

Some patients under thalamic deep brain stimulation (DBS) for essential tremor (ET) experience habituation of tremor reduction. The nucleus ventralis intermedius (Vim) is the current main target side for ET in DBS. However, the dentatorubrothalamic tract (DRTT) is considered the relevant structure to stimulate. We investigated the distance between the active contact of the DBS electrode and the DRTT and compared this distance in patients with habituation of tremor reduction and good responders. In this retrospective study, we performed deterministic fiber tracking of the DRTT in 6 patients (12 hemispheres) with ET who underwent DBS in the Vim. We subsequently measured the distance between the active contact of the electrode and the ipsilateral DRTT in both hemispheres. The clinical tremor response of those 6 patients was analyzed accordingly. The distance between the active contact and the DRTT in patients with better and constant clinical tremor reduction was shorter (mean distance: 2.9 ± 2.2 mm standard deviation [SD]) than in patients who showed habituation of their response (mean distance: 6.1 ± 3.9 mm SD). After re-placement of a thalamic electrode inside the DRTT in one patient who experienced unsatisfying tremor reduction due to habituation of stimulation, the tremor alleviation was significant and persistent at a 13-month follow-up. This retrospective analysis suggests that recurrence of ET tremor under chronic DBS might be associated with a larger distance between the DRTT and the active lead contact, in comparison with the smaller distances in patients with persistently good tremor control.

A structural magnetic resonance imaging review of clinical motor outcomes from deep brain stimulation in movement disorders

“… 72 , 74‐80 , 82 In two studies, clinical testing for motor symptoms was not assessed using standardized clinical scales. 73 , 81 …”

“…The simplest approach to tractography identified in this review was deterministic diffusion tensor imaging (DTI), 28 , 42 , 47 , 51 , 55 , 73 , 74 , 81 which models a single orientation of voxel-wise diffusion using a tensor ( Fig. 3B ).…”

“… 108 A total of three studies quantified the overlap of VTA with specific neural regions or tracts of interest. 23 , 28 , 47 , 51 , 60 , 69 , 73‐75 , 81 A similar method used in 10 studies measured the distance (or proximity) of reconstructed contacts/VTA to specific tracts. 23 , 28 , 47 , 51 , 60 , 69 , 73‐75 , 81 Another method involved assessing quantitative diffusion metrics from tensor-reconstructed tracts, identified in three studies ( Fig.…”

Loss of long‐term benefit from VIM‐DBS in essential tremor: A secondary analysis of repeated measurements

“… 53 , 59 , 60 , 61 , 62 , 63 However, Murata et al 60 reported that PSA may also cause a loss of DBS benefits. Anthofer et al 64 found that patients with a long distance from contact with DRTT fibers are more likely to experience DBS tolerance. Further research is needed to explain the benefit loss in terms of the locations of DBS leads.…”

Habituation After Deep Brain Stimulation in Tremor Syndromes: Prevalence, Risk Factors and Long-Term Outcomes

“…Surgical approaches to habitation may include reimplantation of DBS with a repositioned electrode optimized to closer proximity to the dentatorubrothalamic tract (as imaged by diffusion tensor tractography MRI) which may achieve superior tremor control with less habituation ( 86 ). Moreover, there is growing evidence that closer targeting of MRI-visualized dentatorubrothalamic tract (DRT) provides more effective and efficient tremor control ( 87 , 88 ) and it remains to be seen whether this approach of targeting DRT deliberately will confer lower rates of habituation in the longer term.…”