Article
Deep brain stimulation in subthalamic and ventral intermediate nucleus for therapy of refractory tremor – are we stimulating two structures or one structure at two different points?
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Authors
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Michael Fiechter
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Andreas Nowacki
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Markus F. Oertel
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Jens Fichtner
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Michael Schüpbach
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Ines Debove
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Lenard Lachenmayer
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Roland Wiest
- Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Claudio Pollo
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| Published: | June 2, 2015 |
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Outline
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Objective: Deep brain stimulation (DBS) in the subthalamic nucleus (STN) or ventral intermediate nucleus (VIM) has shown to be effective for the treatment of tremor in patients suffering from Parkinson disease (PD) or essential tremor (ET). However, the optimal site of stimulation is still debated. Retrospective studies on electrode position in the VIM pointed out the possibility of stimulated contacts below the thalamus. Similarly, studies performed in the STN reported efficiency above and medial to it. In this study, we retrospectively propose to calculate the site of stimulation of patients implanted in the STN and VIM for PD and ET respectively and discuss the possible common structure involved in DBS for tremor.
Method: 25 patients with tremor either due to PD or ET in whom DBS was successfully performed between 2008 and mid-2012 were included in in this study. The position of the stimulating electrodes (i.e correlated with the best control on tremor) was calculated using postoperative CT co-registrated with preoperative 3 Tesla T2-weighted MR (iPlan Net, Brainlab AG, Germany) and OPTIVISE software (Medtronic Inc., Minneapolis, USA). For each patient, the volume of tissue activated (VTA) was calculated. The student’s t-test was used for statistical analysis. A P<0.05 was considered as statistically significant.
Results: The mean position of the STN stimulating contacts was (in mm) AP=-2.0 ± 1.7, LAT=12.8 ± 1.1, VERT=-0.8 ± 1.6, whereas AP=-5.0 ± 0.9, LAT=14.3 ± 1.6, VERT= 0.9 ± 1.2 for the VIM (P<0.001). The mean radius of the VTA was 4.8 ± 1.1 mm for STN and 5.8 ± 1.8 mm for VIM, respectively. Although the 2 stimulation sites were significantly different in terms of AC-PC coordinates, the VTA co-registrated with the preoperative image of each individual patient interestingly showed a stimulation site inferior to the VIM and superior to the STN in >80% of the cases.
Conclusions: VTA analysis in each individual patient suggests that stimulation of these 2 sites may actually involve a unique structure. According to diffusion tensor imaging (DTI) studies, the dentate-rubro-thalamic tract (DRTT) is crossing this area and could be the optimal point of stimulation. A prospective study is under investigation to confirm these findings.
