Parkinson's disease (PD) and essential tremor (ET) sometimes appear in the same patient, but the nature of this coexistence is a matter of ongoing debate.1 Although deep brain stimulation (DBS) is effective for both disorders, the targeted brain regions differ: the subthalamic nucleus (STN) or pars interna of the globus pallidus is preferred in PD patients and the nucleus ventralis intermedius of the thalamus (Vim) for ET patients. In addition, stimulation of the caudal zona incerta has been suggested for tremor control.2-4 In 1 reported patient with ET and PD, DBS in the STN improved both disorders.5 We present the case of a 50-year-old man who has suffered from ET since he was 5 years old. His mother and brother also suffered from ET. The Whiget Tremor Rating Scale score was 34 points (left, 14; right, 20) and improved to 16 (8/8) points after alcohol intake. Furthermore, he showed progressive signs of PD, which started 2 years ago. Both ET and PD were more dominant on the right side. Apart from the rest tremor, PD signs responded well to levodopa (motor part of the Unified Parkinson's Disease Rating Scale score: 32 points off, 17 points on levodopa). Pharmacological treatment was difficult; treatment for ET was either insufficient (gabapentin, topiramate, alprazolam) or not well tolerated (primidone, propranolol). Dopaminergic drugs (pramipexole, ropinirole, levodopa) caused severe sleepiness. After careful evaluation, we recommended DBS. Although at this point the patient was still more affected by ET, PD symptoms were already significantly limiting the patient's daily activities. Based on the above-mentioned case report, we selected as a target structure the medial STN, neighboring the caudal zona incerta in T2-weighted MRI (Suppl. Fig.; mid-commissural point [MCP]–based coordinates as x/y/z in millimeters: L, −10.72/−5.75/−4.08; R, 10.15/−5.0/−4.08). However, we aimed for an electrode trajectory that allowed the most dorsal poles of the quadripolar electrodes (Medtronic model 3389) to be located as close as possible to the Vim. After 5 microelectrode recordings and intraoperative macrostimulation, and after weighing benefits versus side effects, we implanted the electrodes in the anterior (left side) and lateral (right side) trajectory passing the thalamus and ending down in the STN, but not in proximity of the zona incerta. Fusion of intraoperative stereotactic computed tomography images with preoperative MRI revealed the following MCP-based positions (Suppl. Fig.): c0, −11.18/−2.85/−3.50; c8, 11.21/−2.97/−4.24; c3, −13.17/−0.50/1.70; c11, 14.01/−0.70/−0.56. Projection of the electrodes on a 3-D atlas confirmed the localization of the most ventral poles (c0/c8) in the STN and the most dorsal poles (c3/c11) in the ventrolateral anterior thalamus (Fig. 1 and Suppl. Fig.).6 Reconstruction of the quadripolar electrode placement in a 3-dimensional atlas,6 based on preoperative magnetic resonance imaging and on postoperative computed tomography. A: left side; B: right side. Red nucleus, red; subthalamic nucleus (STN), transparent green; thalamic nuclei—ventral anterior (VA), ventral lateral anterior (VLa), ventral lateral posterior (VLpv or Vim). After bilateral electrode implantation, we first stimulated the left STN to alleviate right-sided symptoms of both PD and ET. However, this did not improve ET (unipolar stimulation of the most ventral pole; amplitude up to 3.5 V; impulse width, 60 μs; frequency, 130 Hz). Conversely, unipolar stimulation of the most dorsal pole (up to 4.2 V/60 μs/130 Hz) only improved ET. Thereafter, we programmed simultaneous unipolar stimulation at both extreme poles (up to 4.2 V/60 μs/130 Hz), but this strategy improved neither PD nor ET. Finally, we employed an interleaving stimulation of the same extreme poles (ventral: 3.3 V, dorsal: 4.3 V, both 60 μs/125 Hz). For the first time, symptoms of both PD and ET were significantly improved (Video). In contrast to an earlier case report,5 stimulation of the STN alone was not beneficial for ET in this patient. And simultaneous unipolar stimulation at both extreme poles was not efficacious for any symptom. However, an interleaving stimulation strategy, that is, alternating unipolar impulses with different amplitudes for the extreme poles in the STN and the ventrolateral anterior thalamic region near the Vim was successful in improving both PD and ET. The importance of pulse timing (simultaneous vs interleaving) may be related to temporal integration in the receiving brain areas. Video 1. In the video sequences, the patient shows signs of Parkinson's disease (PD) and of essential tremor (ET) before and 6 months after deep brain stimulation, all off medication. All postoperative sequences are captured under interleaving stimulation of the extreme poles of the left electrode. The right electrode was programmed with bipolar stimulation of the 2 caudal poles in the subthalamic nucleus: sequence 1, PD rest tremor; sequence 2, PD akinesia; sequence 3, postural ET; sequence 4, action ET. We thank Jessica Imbach for the careful revision of this text. Author Roles: Christian Baumann—conception of the project, treatment of the patient, writing the first draft of the manuscript. Lukas Imbach—conception of the project, treatment of the patient, writing the first draft of the manuscript. Heide Vogel—programming of the deep brain stimulator, data collection, review and critique of the manuscript. Mechtild Uhl—performance of all levodopa tests, videotaping, review and critique of the manuscript. Johannes Sarnthein—projection of electrode position onto the atlas (Fig. 1), review and critique of the manuscript. Oguzkan Sürücü—conception of the project and surgical plan, treatment of the patient, review and critique of the manuscript. Financial Disclosures: Lukas Imbach, Heide Vogel, Mechtild Uhl, and Johannes Sarnthein have nothing to disclose. Christian R Baumann received competitive grant money from the Swiss National Foundation and from Parkinson Switzerland for other projects and has received honoraria for advisory boards from UCB Pharmaceuticals. Oguzkan Sürücü received travel costs by industry. Additional Supporting Information may be found in the online version of this article. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Christian R. Baumann MD*, Lukas L. Imbach MD*, Heide Baumann-Vogel MD*, Mechtild Uhl*, Johannes Sarnthein PhD , Oguzkan Sürücü , * Department of Neurology, UniversitätsSpital Zürich Zürich, Switzerland, Department of Neurosurgery, UniversitätsSpital Zürich Zürich, Switzerland
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Baumann et al. (2012) studied this question.