Abstract
BackgroundTherapeutic effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson’s disease (PD) may in parts be attributed to the stimulation of white matter near the targeted structure. The dentato-rubro-thalamic (DRT) tract supposed to improve tremor control in patients with essential tremor could be one candidate structure. The aim of this study was to investigate the effect of stimulation proximity to the DRT on tremor control in PD patients treated with STN-DBS.MethodsFor this retrospective analysis, we included 36 consecutive patients (median age 65.5 years) treated with STN-DBS for disabling motor symptoms including tremor. Stereotactic implantation of DBS electrodes into the motor area of the STN was performed using direct MRI-based targeting and intraoperative microelectrode recording. Tremor severity was assessed preoperatively and at regular intervals postoperatively (Unified Parkinson’s Disease Rating Scale III). The DRT was visualized in 60 hemispheres after probabilistic fiber tracking (3-T MRI). The position of active electrode contacts was verified on intraoperative stereotactic X-rays and postoperative CT images after co-registration with 3D treatment planning MRI/CT images. We determined the shortest distance of active contacts to the ipsilateral DRT tracts on perpendicular view slices and correlated this value with tremor change percentage.ResultsTwelve patients had unilateral tremor only, and accordingly, 12 hemispheres were excluded from further imaging analysis. The remaining 60 hemispheres were associated with contralateral resting tremor. Active brain electrode contacts leading to resting tremor improvement (46 hemispheres) had a significantly shorter distance to the DRT (1.6 mm (0.9–2.1) [median (25th–75th percentiles)]) compared with contacts of non-responders (14 hemispheres, distance: 2.8 mm (2–4.6), p < 0.001).ConclusionThis retrospective analysis suggests that in STN-DBS, better tremor control in PD patients correlates with the distance of active electrode contacts to the DRT. Tractography may optimize both individually DBS targeting and postoperative adjustment of stimulation parameters.
Highlights
The predominant aspects of the motor symptoms associated with Parkinson’s disease (PD) classify the patients into an akinetic-rigid, tremor-dominant, and balanced motor PD subtype
Pathophysiological mechanisms supposed to be involved in tremor genesis are tremor of the extremity, tremor mediated through reflexes of the central nervous system (CNS), malfunction of feed forward loops within the CNS, and central oscillation
Impulse generator settings associated with the best individual improvement of motor symptoms were mean voltage 2.3 V for 14 patients with non-segmented electrodes, mean amplitude 3 mA for the remaining 22 patients with segmented electrodes, mean pulse width 63.3 μs, and mean frequency 141.2 Hz
Summary
The predominant aspects of the motor symptoms associated with Parkinson’s disease (PD) classify the patients into an akinetic-rigid, tremor-dominant, and balanced motor PD subtype. Chronic high-frequency electrical stimulation (deep brain stimulation (DBS)) of the subthalamic nucleus (STN), the ventro-postero-lateral part of the globus pallidus internus (VPL-GPi), and the nucleus ventralis intermedius of the thalamus (V.im.) according to Hassler’s classification) reduces effectively Parkinsonian rest tremor. These anatomical structures are relay nuclei of the basal ganglia loop and/or the cerebello-thalamic loop. Even though the mode of action is not completely unraveled to date, one important therapeutic mechanism of DBS is the disruption and overriding of network-wide pathological signals leading to electrical stabilization of diseased neuronal networks In this context, myelinated axons and white matter are the assumed target structures for DBS effects [31]. We determined the shortest distance of active contacts to the ipsilateral DRT tracts on perpendicular view slices and correlated this value with tremor change percentage
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
