Deep Brain Stimulation of the Caudal Zona Incerta: Tremor Control in Relation to the Location of Stimulation Fields

Abstract

Background: The caudal zona incerta (cZi) and posterior subthalamic area (PSA) are an emerging deep brain stimulation (DBS) target for essential tremor (ET). Objectives: To evaluate the efficacy of tremor control in relation to the anatomical locations of stimulation fields in 50 patients with ET and DBS of the cZi. Methods: A total of 240 contacts were evaluated separately with monopolar stimulation, and amplitudes were optimized for improvement of tremor and hand function. Stimulation fields, i.e., volumes of neural activation, were simulated for each optimized setting and assembled into probabilistic stimulation maps (PSMs). Results: There were differences in the anatomical distribution of PSMs associated with good versus poor tremor control. The location of PSMs which achieved good and excellent tremor control corresponded well with the PSM for the clinically used settings, and they were located within the superior part of the PSA. Conclusions: PSMs may serve as a useful tool for defining the most efficacious anatomical location of stimulation. The best tremor control in this series of cZi DBS was achieved with stimulation of the superior part of the PSA, which corresponds to the final part of the cerebellothalamic projections before they reach the ventral lateral thalamus.

Unilateral Left Deep Brain Stimulation of the Caudal Zona Incerta Is Equally Effective on Voice Tremor as Bilateral Stimulation: Evidence from 7 Patients with Essential Tremor

“…Since the thalamic and the subthalamic targets are in close proximity, it is conceivable that stimulation of thalamic regions may have contributed to the observed voice tremor reduction. However, for most patients here, the active contacts were located well below the intercommissural line, which suggests that the patients were receiving stimulation primarily within the PSA [6].…”

“…Electrode location was confirmed by merging the preoperative MRI with a postoperative CT using the Framelink ® Planning Station (Medtronic Inc.), and contact coordinates were calculated in relation to the mid-commissural point. All ac- tive contacts during left unilateral stimulation were located below the intercommissural line (Table 1), i.e., within the PSA [6].…”

Comparison of tractography‐assisted to atlas‐based targeting for deep brain stimulation in essential tremor

“…Plaha and colleagues in their analysis of Parkinson's disease (PD) patients found contacts placed in the cZI had better motor control (including significantly improved tremor control) than those placed in STN proper. Fytagoridis and colleagues in an analysis of anatomical location of electrode contacts after optimization of parameters at clinically useful settings demonstrated through probabilistic stimulation mapping that the contacts placed in the superior part of the PSA had superior tremor control than those elsewhere in the cZI. They state that such efficacy is most likely attributed to greater modulation of the cerebellothalamic fibers, which are more tightly concentrated at this location.…”

“…The use of diffusion tensor tractographic methods has shown that these targets likely lie along part of the same cerebello‐thalamic‐cortical network, or the dentato‐rubro‐thalamic tract (DRTt), where the more proximal targets intercept tract fibers that are more concentrated before fanning out in the thalamus . Some experts contend that modulation of the DRTt fibers may, in fact, be responsible for tremor suppression applied at any of these targets …”

Prelemniscal Lesion for Selective Improvement of Parkinson Disease Tremor

“…In the posterior subthalamic area, 2 targets have been proposed for controlling motor symptoms of PD, i.e., the caudal zona incerta (Zic) [19-21] and the posterior subthalamic white matter (Raprl) [22-24]. Given that the posterior subthalamic area is rather small, both targets are in close proximity in terms of their x (14.0 vs. 11.69 mm), y (5.8 vs. 6.73 mm behind the mid commissural point), and z (2.1 vs. 4.38 mm below the AC-PC level) coordinates [25].…”