Targeting the hot spot in a patient with essential tremor and Parkinson's disease: Tractography matters.

INTRODUCTION: Thalamic ventralis intermedius deep brain stimulation (VIM-DBS) is generally effective in treating refractory tremor in Parkinson's disease (PD) and in essential tremor (ET), but some patients do not respond well due to side effects or from loss of the effect of stimulation over time. The caudal zona incerta (ZI) has emerged as a promising target in ET, and the effects of ZI-DBS on PD tremor are less studied. Here, we describe a rare situation in which both ET and PD coexist in a 72-year-old male referred for ZI-DBS due to refractory tremor. The aim of this study was to evaluate whether there was a difference in the area stimulated to improve each type of tremor and whether tractography could improve and predict motor outcome. METHODS: Two months after the surgery, in order to define which of the cathodes was the most effective towards improving the tremor and parkinsonian symptoms, a double-blinded, monopolar evaluation was conducted on both hemispheres separately. Once the best contact and parameters were defined, the volume of tissue activation (VTA) was represented spatially for each type of tremor and, finally, the image model was fused with the tractography. RESULTS: For both types of tremor, the hot spot stimulated region achieved the dentato-rubro-thalamic tract (DRTT) at the higher fiber density region. The DRTT fibers were asymmetrical between the right and left hemispheres. CONCLUSION: Regardless of the type of tremor, DRTT can be the most effective region for stimulation. Tractography should be considered when planning the surgical target since the DRTT is not always symmetrical, and the reconstruction of the VTA together with the tractography can greatly improve the DBS programming, and, probably, the patient's outcome to the stimulation.

Simultaneous bilateral stereotactic procedure for deep brain stimulation implants: a significant step for reducing operation time.

OBJECT Currently, bilateral procedures involve 2 sequential implants in each of the hemispheres. The present report demonstrates the feasibility of simultaneous bilateral procedures during the implantation of deep brain stimulation (DBS) leads. METHODS Fifty-seven patients with movement disorders underwent bilateral DBS implantation in the same study period. The authors compared the time required for the surgical implantation of deep brain electrodes in 2 randomly assigned groups. One group of 28 patients underwent traditional sequential electrode implantation, and the other 29 patients underwent simultaneous bilateral implantation. Clinical outcomes of the patients with Parkinson's disease (PD) who had undergone DBS implantation of the subthalamic nucleus using either of the 2 techniques were compared. RESULTS Overall, a reduction of 38.51% in total operating time for the simultaneous bilateral group (136.4 ± 20.93 minutes) as compared with that for the traditional consecutive approach (220.3 ± 27.58 minutes) was observed. Regarding clinical outcomes in the PD patients who underwent subthalamic nucleus DBS implantation, comparing the preoperative off-medication condition with the off-medication/on-stimulation condition 1 year after the surgery in both procedure groups, there was a mean 47.8% ± 9.5% improvement in the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) score in the simultaneous group, while the sequential group experienced 47.5% ± 15.8% improvement (p = 0.96). Moreover, a marked reduction in the levodopa-equivalent dose from preoperatively to postoperatively was similar in these 2 groups. The simultaneous bilateral procedure presented major advantages over the traditional sequential approach, with a shorter total operating time. CONCLUSIONS A simultaneous stereotactic approach significantly reduces the operation time in bilateral DBS procedures, resulting in decreased microrecording time, contributing to the optimization of functional stereotactic procedures.