1; M. Nevrlý
2; P. Otruba
2; L. Hrabálek
1; M. Vaverka
1; P. Kaňovský
Department of Neurosurgery, University Hospital Olomouc
1; Department of Neurology, University Hospital Olomouc
Cesk Slov Neurol N 2019; 115(3): 342-344
Aim:Deep brain stimulation (DBS) is a very effective procedure for the treatment of idiopathic Parkinson‘s disease (PD), essential tremor and dystonia. The authors describe a method of DBS using frameless and fiducial-less system Nexframe (Medtronic), S8 navigation (Medtronic) and O-arm (Medtronic) for placing DBS electrodes in four patients (8 electrodes). To our knowledge, this is only the second centre in the world to have used this method.
Methods:Two adult patients with PD and two with essential tremor were indicated to bilateral DBS. Baseline neurological status and DBS-related improvement in motor function were measured using patients‘ diaries, Unified Parkinson‘s Disease Rating Scale and Clinical Global Improvement tests. The implantation of DBS leads was performed using MRI, preoperative CT examination and their fusion with perioperative O-arm imaging. The accuracy was checked using the same methodology as the Nexframe system. We also evaluated average time of surgery for Leksell frame-based surgery, Nexframe procedure and fiducial-less procedure.
Results: The accuracy and patient outcome were excellent, with a total error of 2.49 mm, without any complication. Average times of surgeries were: Leksell frame 290 min, Nexframe system 222 min and last procedure 201 min.
Conclusion:Implantation of DBS electrodes using frameless and fiducial-less system is a very useful and technically feasible procedure with excellent patient toleration. It will be necessary to operate in this way on many more patients to prove efficacy of this method, but from our point of view this method appears very promising
Four patients (eight electrodes) were implanted using the frameless and fiducial-less technique in October 2018. Two patients were treated for PD and the other two for tremor. PD patients met the Movement Disorder Society Clinical Diagnostic Criteria for Parkinson‘s Disease  and patients treated for tremor had pharmacoresistant essential tremor. All patients were fully informed about the procedure and the procedure was performed by a single surgeon (D. K.) and neurologists (M. N., P. O.)
Two MRI sets were obtained a few days before the surgery for PD patient: 1. volumetric 3D Gd-enhanced gradient echo MRI sequence covering the whole brain in 1 mm axial slices, mainly for trajectory planning and 2. T2 images turbo spin echo 2 mm slices for the borders of subthalamic nucleus (STN). For tremor patients, we used tractography and segmentation of thalamic nuclei according to 1. high resolution inversion recovery T1 covering the whole brain and 2. diffusion tensor imaging sequence: non-diffusion weighted data set, 30– 60 diffusion gradient, as high a resolution as possible.
CT scan covering whole head was obtained for the best fusion with perioperative O-arm
imaging (Medtronic, Dublin, Ireland).
At the beginning of the surgery, the 3D O-arm scan was obtained and fused with preoperative MRI and CT image in the S8 stereotactic navigation planning software (Medtronic). The target points for the tips of the electrodes were selected using a combination of direct (visualized) and indirect targeting in PD and with indirect targeting in tremor combined with MRI tractography and segmentation of thalamic nuclei. The trajectories were visualized on the volumetric MRI images using “navigation” views. Small adjustments were then made to avoid traversing the cortical veins and dural venous lakes (easily seen on Gd-enhanced images) and lateral ventricles. Surgical procedures were carried out in two stages during the same day. The first stage, implantation of the DBS electrodes was carried out on the patient whilst awake, and the second stage was implantation of the internal pulse generator, performed under general anaesthesia.
To perform MER in STN-DBS, four MER/ macrostimulation needles were placed in an array
with central, lateral, anterior and posterior to delineate the borders of the nucleus. A starting point for the STN 10 mm above the MRI-based target was set and the microelectrodes were advanced in steps of 500 μm towards the target by an electric microdrive.
Lead anchoring and implantable pulse generator placement
Leads were anchored to the skull with a lead anchoring device (Stimlock®, Medtronic). After scalp closure, the surgery continued under the general anaesthesia and the lead extenders and pulse generators were placed.
Deep brain stimulation is basically performed by two methods, one using any stereotactic frame and the other using any frameless system with small fiducials attached to the skull. This new method excludes fiducials and uses perioperative O-arm imaging and an online navigation system. None of the systems are strictly accurate and average error is between 1– 2 mm. There are few weak points in the method that can lead to inaccuracy such as fusion between MRI, CT and O-arm, but the newest navigation system has an error of about 1– 2 imaging voxels . Urgosik et al analyzed accuracy of DBS placement using the Leksell frame according to intraoperative monitoring with very good results and minimum complications . Rohlfing et al found reduced accuracy of stereotactic frames because of torque introduced by the effect of weight bearing on the frame . Krahulík et al and Holloway et al confirmed comparable accuracy of frameless systems to the frame-based systems [10,14].
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