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  • 1.
    Blomstedt, Patric
    et al.
    Umeå University, Sweden .
    Fytagoridis, Anders
    Umeå University, Sweden .
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Linder, Jan
    Umeå University, Sweden .
    Forsgren, Lars
    Umeå University, Sweden .
    Hariz, Marwan I.
    Umeå University, Sweden .
    Unilateral caudal zona incerta deep brain stimulation for Parkinsonian tremor2012In: Parkinsonism & Related Disorders, ISSN 1353-8020, E-ISSN 1873-5126, Vol. 18, no 10, 1062-1066 p.Article in journal (Refereed)
    Abstract [en]

    Background: The subthalamic nucleus is currently the target of choice in deep brain stimulation (DBS) for Parkinsons disease (PD), while thalamic DBS is used in some cases of tremor-dominant PD. Recently, a number of studies have presented promising results from DBS in the posterior subthalamic area, including the caudal zona incerta (cZi). The aim of the current study was to evaluate cZi DBS in tremor-dominant Parkinsons disease. less thanbrgreater than less thanbrgreater thanMethods: 14 patients with predominately unilateral tremor-dominant PD and insufficient relief from pharmacologic therapy were included and evaluated according to the motor part of the Unified Parkinson Disease Rating Scale (UPDRS). The mean age was 65 +/- 6.1 years and the disease duration 7 +/- 5.7 years. Thirteen patients were operated on with unilateral cZi DBS and 1 patient with a bilateral staged procedure. Five patients had non-L-dopa responsive symptoms. The patients were evaluated on/off medication before surgery and on/off medication and stimulation after a minimum of 12 months after surgery. less thanbrgreater than less thanbrgreater thanResults: At the follow-up after a mean of 18.1 months stimulation in the off-medication state improved the contralateral UPDRS III score by 47.7%. Contralateral tremor, rigidity, and bradykinesia were improved by 82.2%, 34.3%, and 26.7%, respectively. Stimulation alone abolished tremor at rest in 10 (66.7%) and action tremor in 8 (533%) of the patients. less thanbrgreater than less thanbrgreater thanConclusion: Unilateral cZi DBS seems to be safe and effective for patients with severe Parkinsonian tremor. The effects on rigidity and bradykinesia were, however, not as profound as in previous reports of DBS in this area.

  • 2.
    Cubo, Ruben
    et al.
    Uppsala University, Sweden.
    Medvedev, Alexander
    Uppsala University, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Model-Based Optimization of Individualized Deep Brain Stimulation Therapy2016In: IEEE DESIGN and TEST, ISSN 2168-2356, Vol. 33, no 4, 74-81 p.Article in journal (Refereed)
    Abstract [en]

    n/a

  • 3.
    Cubo, Ruben
    et al.
    Uppsala University, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Medtron Eindhoven Design Centre, Netherlands.
    Medvedev, Alexander
    Uppsala University, Sweden.
    Electric Field Modeling and Spatial Control in Deep Brain Stimulation2015In: 2015 54TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2015, 3846-3851 p.Conference paper (Refereed)
    Abstract [en]

    Deep Brain Stimulation (DBS) is an established treatment, in e.g. Parkinsons Disease, whose underlying biological mechanisms are unknown. In DBS, electrical stimulation is delivered through electrodes surgically implanted into certain regions of the brain of the patient. Mathematical models aiming at a better understanding of DBS and optimization of its therapeutical effect through the simulation of the electrical field propagating in the brain tissue have been developed in the past decade. The contribution of the present study is twofold: First, an analytical approximation of the electric field produced by an emitting contact is suggested and compared to the numerical solution given by a Finite Element Method (FEM) solver. Second, the optimal stimulation settings are evaluated by fitting the field distribution to a target one to control the spread of the stimulation. Optimization results are compared to those of a geometric approach, maximizing the intersection between the target and the activated volume in the brain tissue and reducing the stimulated area beyond said target. Both methods exhibit similar performance with respect to the optimal stimuli, with the electric field control approach being faster and more versatile.

  • 4.
    Cubo, Ruben
    et al.
    Uppsala University, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Medvedev, Alexander
    Uppsala University, Sweden.
    Target coverage and selectivity in field steering brain stimulation2014In: 2014 36TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), Institute of Electrical and Electronics Engineers (IEEE), 2014, 522-525 p.Conference paper (Refereed)
    Abstract [en]

    Deep Brain Stimulation (DBS) is an established treatment in Parkinsons Disease. The target area is defined based on the state and brain anatomy of the patient. The stimulation delivered via state-of-the-art DBS leads that are currently in clinical use is difficult to individualize to the patient particularities. Furthermore, the electric field generated by such a lead has a limited selectivity, resulting in stimulation of areas adjacent to the target and thus causing undesirable side effects. The goal of this study is, using actual clinical data, to compare in silico the stimulation performance of a symmetrical generic lead to a more versatile and adaptable one allowing, in particular, for asymmetric stimulation. The fraction of the volume of activated tissue in the target area and the fraction of the stimulation field that spreads beyond it are computed for a clinical data set of patients in order to quantify the lead performance. The obtained results suggest that using more versatile DBS leads might reduce the stimulation area beyond the target and thus lessen side effects for the same achieved therapeutical effect.

  • 5.
    Dembek, Till A.
    et al.
    Department of Neurology, University of Cologne, Cologne, Germany; Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne, Germany.
    Barbe, Michael T
    Department of Neurology, University of Cologne, Cologne, Germany.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Medtronic Neuromodulation, Medtronic Eindhoven Design Center, Eindhoven, The Netherlands.
    Hoevels, Mauritius
    Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne, Germany.
    Visser-Vandewalle, Veerle
    Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne, Germany.
    Fink, Gereon R
    Department of Neurology, University of Cologne, Cologne, Germany.
    Timmermann, Lars
    Department of Neurology, University of Cologne, Cologne, Germany.
    Probabilistic mapping of deep brain stimulation effects in essential tremor2017In: NeuroImage: Clinical, ISSN 0353-8842, E-ISSN 2213-1582, Vol. 13Article in journal (Refereed)
    Abstract [en]

    Objective

    To create probabilistic stimulation maps (PSMs) of deep brain stimulation (DBS) effects on tremor suppression and stimulation-induced side-effects in patients with essential tremor (ET).

    Method

    Monopolar reviews from 16 ET-patients which consisted of over 600 stimulation settings were used to create PSMs. A spherical model of the volume of neural activation was used to estimate the spatial extent of DBS for each setting. All data was pooled and voxel-wise statistical analysis as well as nonparametric permutation testing was used to confirm the validity of the PSMs.

    Results

    PSMs showed tremor suppression to be more pronounced by stimulation in the zona incerta (ZI) than in the ventral intermediate nucleus (VIM). Paresthesias and dizziness were most commonly associated with stimulation in the ZI and surrounding thalamic nuclei.

    Discussion

    Our results support the assumption, that the ZI might be a very effective target for tremor suppression. However stimulation inside the ZI and in its close vicinity was also related to the occurrence of stimulation-induced side-effects, so it remains unclear whether the VIM or the ZI is the overall better target. The study demonstrates the use of PSMs for target selection and evaluation. While their accuracy has to be carefully discussed, they can improve the understanding of DBS effects and can be of use for other DBS targets in the therapy of neurological or psychiatric disorders as well. Furthermore they provide a priori information about expected DBS effects in a certain region and might be helpful to clinicians in programming DBS devices in the future.

    Abbreviations: DBS, Deep brain stimulation; ET, Essential tremor; PSA, Posterior subthalamic area; PSM, Probabilistic stimulation map; VIM, Ventral intermediate nucleus; VNA, Volume of neural activation; ZI, Zona incerta

  • 6.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Didzar, Nil
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Biochemical monitoring and simulation of the electric field during deep brain stimulation (oral)2010Conference paper (Other academic)
  • 7.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Didzar, Nil
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A finite element model for biochemical monitoring in the brain during deep brain stimulation (poster)2010Conference paper (Refereed)
  • 8.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Dizdar, Nil
    Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A Finite Model for Biochemical Monitoring in the Brain during Deep Brain Stimulation (oral)2010Conference paper (Refereed)
  • 9.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Software for Patient Specific Modeling and Simulation of Deep Brain Stimulation (poster)2011Conference paper (Refereed)
  • 10.
    Fytagoridis, A.
    et al.
    Department of Pharmacology and Clinical Neuroscience, Section of Neurosurgery, Umeå University, Sweden; Department of Neurosurgery, Karolinska University Hospital, Stockholm, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Blomstedt, P.
    Department of Pharmacology and Clinical Neuroscience, Section of Neurosurgery, Umeå University, Sweden.
    Stimulation-induced side effects in the posterior subthalamic area: distribution, characteristics and visualization2013In: Clinical neurology and neurosurgery (Dutch-Flemish ed. Print), ISSN 0303-8467, E-ISSN 1872-6968, Vol. 15, no 1, 65-71 p.Article in journal (Refereed)
    Abstract [en]

    Objective: The posterior subthalamic area (PSA) is an emerging but relatively unexplored target for DBS treatment of tremor. The aim of the study was to explore the area further by evaluating the spatial distribution and the characteristics of stimulation-induced side effects in this area. Methods: Twenty-eight patients with essential tremor (ET) implanted with 33 DBS electrodes were evaluated concerning stimulation-induced side effects by testing each contact separately one year after surgery. The location of the side effects were plotted on axial slides of the Morel Stereotactic Atlas and a 3-dimensional model of the area for visualization was created. Results: Visualization of the contacts eliciting stimulation-induced side effects demonstrated that identical responses can be elicited from various points in the PSA and its vicinity. The majority of contacts inducing muscular affection and cerebellar symptoms, including dysarthria, could not be attributed to an effect on the internal capsule. Paresthesias, affecting various body parts were elicited throughout the area without a clear somatotopic pattern. Conclusion: Stimulation-induced side effects in the PSA and its vicinity are difficult to attribute to certain anatomical areas as the same response can be induced from various locations, and are thus of limited localizing value.

  • 11.
    Fytagoridis, Anders
    et al.
    Karolinska University Hospital.
    Sandvik, Ulrika
    Umeå University.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Bergenheim, Tommy
    Umeå University.
    Blomstedt, Patric
    Umeå University.
    Long term follow-up of deep brain stimulation of the caudal zona incerta for essential tremor2012In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 83, no 3, 258-262 p.Article in journal (Refereed)
    Abstract [en]

    Purpose The ventral intermediate nucleus of thalamus is the standard target for deep brain stimulation (DBS) in essential tremor (ET). However, favourable data have recently highlighted the caudal zona incerta (cZi) as an alternative target. Reports concerning the long-term results are however lacking, and we have therefore evaluated the long-term effects in our patients with ET and cZi DBS. less thanbrgreater than less thanbrgreater thanMethods 18 patients were evaluated using the Essential Tremor Rating Scale (ETRS) before and on-/off-stimulation at 1 and 3-5 years after surgery (mean 48.5+/-10.6 months). Two patients were operated on bilaterally but all electrodes were evaluated separately. The stimulation parameters were recorded and the stimulation strength calculated. less thanbrgreater than less thanbrgreater thanResults A baseline total ETRS mean score of 46.0 decreased to 21.9 (52.4%) at the final evaluation. On the treated side, tremor of the upper extremity (item 5 or 6) improved from 6.1 to 0.5 (91.8%) and hand function (items 11-14) improved from 9.3 to 2.0 (78.0%). Activities of daily living improved by 65.8%. There was no increase in stimulation strength over time. less thanbrgreater than less thanbrgreater thanConclusion cZi DBS is a safe and effective treatment for the long term suppression of ET.

  • 12.
    Fytagoridis, Anders
    et al.
    Umeå University, Sweden .
    Sjoberga, Rickard L.
    Umeå University, Sweden .
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredricks, Anna
    Umeå University, Sweden .
    Nyberg, Lars
    Umeå University, Sweden .
    Blomstedt, Patric
    Umeå University, Sweden .
    Effects of Deep Brain Stimulation in the Caudal Zona Incerta on Verbal Fluency2013In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 91, no 1, 24-29 p.Article in journal (Refereed)
    Abstract [en]

    Background: Deep brain stimulation (DBS) of the caudal zona incerta (cZi) is a relatively unexplored and promising treatment in patients with severe essential tremor (ET). Preliminary data further indicate that the ability to produce language may be slightly affected by the treatment. Objective: To evaluate the effects on verbal fluency following cZi DBS in patients with ET. Method: Seventeen consecutive patients who had undergone DBS of the cZi for ET were tested regarding verbal fluency before surgery, 3 days after surgery and after 1 year. Ten patients were also evaluated by comparing performance on versus off stimulation after 1 year. Results: The total verbal fluency score decreased slightly, but significantly, from 22.7 (SD = 10.9) before surgery to 18.1 (SD = 7.5) 3 days after surgery (p = 0.036). After 1 year the score was nonsignificantly decreased to 20.1 (SD = 9.7, p = 0.2678). There was no detectable difference between stimulation on and off after 1 year. Conclusion: There was a tendency of an immediate and mostly transient postoperative decline in verbal fluency following cZi DBS for ET. In some of the patients this reduction was, however, more pronounced and also sustained over time.

  • 13.
    Fytagoridis, Anders
    et al.
    Department of Pharmacologyand Clinical Neuroscience, Section of Neurosurgery, Umeå University, Umeå, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Samuelsson, Jörgen
    Unit of Functional and Stereotactic Neurosurgery, Department of Pharmacology and Clinical Neuroscience, Umeå University, Umeå.
    Blomstedt, Patric
    Department of Pharmacology and Clinical Neuroscience, Division of Neurosurgery, Umeå University, Umeå, Sweden.
    Deep Brain Stimulation of the Caudal Zona Incerta: Tremor Control in Relation to the Location of Stimulation Fields2016In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 94, no 6, 363-370 p.Article in journal (Refereed)
    Abstract [en]

    Background: The caudal zona incerta (cZi) and posterior subthalamic area (PSA) are an emerging deep brain stimulation (DBS) target for essential tremor (ET). Objectives: To evaluate the efficacy of tremor control in relation to the anatomical locations of stimulation fields in 50 patients with ET and DBS of the cZi. Methods: A total of 240 contacts were evaluated separately with monopolar stimulation, and amplitudes were optimized for improvement of tremor and hand function. Stimulation fields, i.e., volumes of neural activation, were simulated for each optimized setting and assembled into probabilistic stimulation maps (PSMs). Results: There were differences in the anatomical distribution of PSMs associated with good versus poor tremor control. The location of PSMs which achieved good and excellent tremor control corresponded well with the PSM for the clinically used settings, and they were located within the superior part of the PSA. Conclusions: PSMs may serve as a useful tool for defining the most efficacious anatomical location of stimulation. The best tremor control in this series of cZi DBS was achieved with stimulation of the superior part of the PSA, which corresponds to the final part of the cerebellothalamic projections before they reach the ventral lateral thalamus.

  • 14.
    Reich, Martin M.
    et al.
    University Hospital Wuerzburg, Germany; Julius Maximilian University, Germany.
    Brumberg, Joachim
    Julius Maximilian University, Germany; University Hospital, Germany.
    Pozzi, Nicolo G.
    University Hospital Wuerzburg, Germany; Julius Maximilian University, Germany.
    Marotta, Giorgio
    Fdn IRCCS Ca Granda Osped Maggiore Policlin, Italy.
    Roothans, Jonas
    Medtron Eindhoven Design Centre, Netherlands.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Medtron Eindhoven Design Centre, Netherlands.
    Musacchio, Thomas
    University Hospital Wuerzburg, Germany; Julius Maximilian University, Germany.
    Lopiano, Leonardo
    University of Turin, Italy.
    Lanotte, Michele
    University of Turin, Italy.
    Lehrke, Ralph
    St Barbara Klin, Germany.
    Buck, Andreas K.
    Julius Maximilian University, Germany; University Hospital, Germany.
    Volkmann, Jens
    University Hospital Wuerzburg, Germany; Julius Maximilian University, Germany.
    Isaias, Ioannis U.
    University Hospital Wuerzburg, Germany; Julius Maximilian University, Germany.
    Progressive gait ataxia following deep brain stimulation for essential tremor: adverse effect or lack of efficacy?2016In: Brain, ISSN 0006-8950, E-ISSN 1460-2156, Vol. 139, 2948-2956 p.Article in journal (Refereed)
    Abstract [en]

    Thalamic deep brain stimulation is a mainstay treatment for severe and drug-refractory essential tremor, but postoperative management may be complicated in some patients by a progressive cerebellar syndrome including gait ataxia, dysmetria, worsening of intention tremor and dysarthria. Typically, this syndrome manifests several months after an initially effective therapy and necessitates frequent adjustments in stimulation parameters. There is an ongoing debate as to whether progressive ataxia reflects a delayed therapeutic failure due to disease progression or an adverse effect related to repeated increases of stimulation intensity. In this study we used a multimodal approach comparing clinical stimulation responses, modelling of volume of tissue activated and metabolic brain maps in essential tremor patients with and without progressive ataxia to disentangle a disease-related from a stimulation-induced aetiology. Ten subjects with stable and effective bilateral thalamic stimulation were stratified according to the presence ( five subjects) of severe chronic-progressive gait ataxia. We quantified stimulated brain areas and identified the stimulation- induced brain metabolic changes by multiple 18 F-fluorodeoxyglucose positron emission tomography performed with and without active neurostimulation. Three days after deactivating thalamic stimulation and following an initial rebound of symptom severity, gait ataxia had dramatically improved in all affected patients, while tremor had worsened to the presurgical severity, thus indicating a stimulation rather than disease-related phenomenon. Models of the volume of tissue activated revealed a more ventrocaudal stimulation in the ( sub) thalamic area of patients with progressive gait ataxia. Metabolic maps of both patient groups differed by an increased glucose uptake in the cerebellar nodule of patients with gait ataxia. Our data suggest that chronic progressive gait ataxia in essential tremor is a reversible cerebellar syndrome caused by a maladaptive response to neurostimulation of the ( sub) thalamic area. The metabolic signature of progressive gait ataxia is an activation of the cerebellar nodule, which may be caused by inadvertent current spread and antidromic stimulation of a cerebellar outflow pathway originating in the vermis. An anatomical candidate could be the ascending limb of the uncinate tract in the subthalamic area. Adjustments in programming and precise placement of the electrode may prevent this adverse effect and help fine-tuning deep brain stimulation to ameliorate tremor without negative cerebellar signs.

  • 15.
    Reich, Martin M.
    et al.
    University Hospital, Germany; Julius Maximilian University, Germany.
    Pozzi, Nicolo G.
    University Hospital, Germany; Julius Maximilian University, Germany.
    Brumberg, Joachim
    Julius Maximilian University, Germany; University Hospital, Germany.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Medtron Eindhoven Design Centre, Netherlands.
    Volkmann, Jens
    University Hospital, Germany; Julius Maximilian University, Germany.
    Isaias, Ioannis U.
    University Hospital, Germany; Julius Maximilian University, Germany.
    Letter: Reply: Clinical approach to delayed-onset cerebellar impairment following deep brain stimulation for tremor in BRAIN, vol 140, issue , pp2017In: Brain, ISSN 0006-8950, E-ISSN 1460-2156, Vol. 140, e28Article in journal (Other academic)
    Abstract [en]

    n/a

  • 16.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Andersson, Mats
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Foltynie, Thomas
    University College London, UK.
    Limousine, Patricia
    University College London, UK.
    Zrinzo, Ludwig
    University College London, UK.
    Hariz, Marwan
    University College London, UK.
    Patient-specific visualization of the DBS-electric field in Tourette syndrome2012Conference paper (Other academic)
  • 17.
    Wårdell, Karin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Sapiens Steering Brain Stimulation B.V., The Netherlands .
    Patient-Specific Modeling and Simulation of Deep Brain Stimulation2011In: Patient-Specific Modeling in Tomorrow's Medicine / [ed] Amit Gefen, Springer Berlin/Heidelberg, 2011, 357-378 p.Chapter in book (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is widely used for reduction of symptoms caused by movement disorders. In this chapter a patient-specific finite element method for modeling and simulation of DBS electric parameters is presented. The individual’s stereotactic preoperative MR-batch of images is used as input to the model in order to classify tissue type and allot electrical conductivity for cerebrospinal fluid, blood and grey as well as white matter. With patient-specific positioning of the DBS electrodes the method allows for investigation of the relative electric field changes in relation to anatomy and DBS-settings. Examples of visualization of the patient-specific electric entities together with the surrounding anatomy are given. The use of the method is exemplified on patients with Parkinson’s disease. Future applications including multiphysics simulations and applicability for new DBS targets and symptoms are discussed.

  • 18.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Software for patient specific simulation and visualization of electric field around deep brain stimulation electrodes (electronic poster)2011Conference paper (Refereed)
  • 19.
    Wårdell, Karin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Diczfalusy, Elin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Åström, Mattias
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Sapiens Steering Brain Stimulation B.V., The Netherlands .
    Martens, Hubert
    2Sapiens Steering Brain Stimulation B.V., The Netherlands.
    Deep Brain Stimulation: Electric Field as a Predictor of Neural Activation2013Conference paper (Refereed)
  • 20.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Kefalopoulou, Zinovia
    Unit of Functional Neurosurgery, Institute of Neurology, University College London, London, UK.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Andersson, Mats
    Linköping University, Department of Biomedical Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Limousin, Patricia
    Unit of Functional Neurosurgery, Institute of Neurology, University College London, London, UK.
    Zrinzo, Ludvic
    Unit of Functional Neurosurgery, Institute of Neurology, University College London, London, UK.
    Hariz, Marwan
    Unit of Functional Neurosurgery, Institute of Neurology, University College London, London, UK / Department of Clinical Neuroscience, Umeå University, Umeå, Sweden.
    Deep Brain Stimulation of the Pallidum Internum for Gilles de la Tourette Syndrome: A Patient-Specific Model-Based Simulation Study of the Electric Field2015In: Neuromodulation (Malden, Mass.), ISSN 1094-7159, E-ISSN 1525-1403, no 2, 90-96 p.Article in journal (Refereed)
    Abstract [en]

    Objectives

    The aim of this study was to investigate the deep brain stimulation (DBS) electric field distribution in proton-density MRI scans visualizing the globus pallidus internus (GPi) of patients with Gilles de la Tourette syndrome (GTS), along with its relation to the anatomy.

    Methods

    Patient-specific brain tissue models (n = 7) with bilateral DBS electrodes in the GPi were set up using the finite element method in five patients who had undergone stereotactic proton-density MRI-guided surgery and showed variable improvement with DBS. Simulations (n = 27) of the electric field were performed and the results visualized on the respective preoperative stereotactic MRI scans. The mean electric field volumes (n = 81) within the 0.1, 0.15, and 0.2 V/mm isosurfaces were calculated and compared with the anatomy.

    Results

    Visualization of the simulated electric field confirmed that the anteromedial limbic GPi was the main stimulated target for four of the patients and the posteromedial sensorimotor GPi for one. Larger volumes extended asymmetrically, with parts of fields stretching into the lamina between GPi and globus pallidus externus and into the internal capsule. There was a high correlation (r = 0.994, n = 54) between volumes and brain sides, but with a systematic shift toward the right side, especially for the larger volumes. Simulations with homogeneous tissue models showed no differences.

    Conclusions

    Patient-specific DBS electric field simulations in the GPi as visualized on proton-density MR scans can be implemented in patients with GTS. Visualization of electric fields together with stereotactic thin-slice MRI can provide further support when predicting anatomical structures possibly influenced by DBS in this complex disorder.

  • 21.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Sapiens Steering Brain Stimulation B.V., The Netherlands .
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Martens, Hubert
    Sapiens Steering Brain Stimulation B.V., The Netherlands.
    Surgical Therapy: Parkinson's disease2014In: Movement DisordersSupplement: Abstracts of the Eighteenth International Congress of Parkinson's Disease and Movement Disorders, John Wiley & Sons, 2014, Vol. 29, 1170-1170 p., Suppl 1:1170Conference paper (Other academic)
    Abstract [en]

    Objective: To analyze the relationship between the electric field and the volume of tissue activated (VTA) during model-based investigations of deep brain stimulation (DBS).

    Background: An important factor for the therapeutic outcome of DBS is the spatial distribution of the stimulation field in the target area. Finite element models and simulations of DBS are increasingly being used to study the distribution of the stimulation field in relation to patient specific anatomy. The stimulation field is often defined as a VTA derived from computational axon models that are coupled to the finite element simulations. This approach however, is not feasible in many research centers due to the complexity of developing a computational axon model, as well as the extensive execution time when solving such models.

    Methods: A detailed computer axon cable model was developed to study axonal activation in response to various DBS stimulation configurations. A range of axon models were set up and coupled to finite element models of DBS. DBS simulations were performed for Medtronic lead model 3389 during monopolar configurations for a range of amplitudes and pulse widths. Activation thresholds for the electric fields were derived by measuring the field strength at the maximum radius of activation for each configuration.

    Results: Simulations showed that the electric field thresholds were related to stimulation amplitude, pulse width, and axon diameter. For large axons, the electric field threshold was not dependent on the amplitude, thus implying a low sensitivity of the electric field curvature.

    Conclusions: Electric field thresholds can be used to predict the VTA during model-based investigations of DBS without the necessity of computer axon models. The use of electric field thresholds may substantially simplify the process of performing model-based investigations of DBS in the future.

  • 22.
    Zsigmond, Peter
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences.
    Dizdar, Nil
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Biochemical Monitoring and Simulation of the Electric Field during Deep Brain Stimulation2009Conference paper (Refereed)
  • 23.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Sapiens Steering Brain Stimulation B.V., The Netherlands .
    Functional brain atlas2014Conference paper (Other academic)
  • 24.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Modelling, Simulaltion, and Visualization of Deep Brain Stimulation2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Deep brain stimulation (DBS) is an effective surgical treatment for neurological diseases such as essential tremor, Parkinsonʹs disease (PD) and dystonia. DBS has so far been used in more than 70 000 patients with movement disorders, and is currently in trial for intractable Gilles de la Tourette’s syndrome, obsessive compulsive disorders, depression, and epilepsy. DBS electrodes are implanted with stereotactic neurosurgical techniques in the deep regions of the brain. Chronic electrical stimulation is delivered to the electrodes from battery-operated pulse generators that are implanted below the clavicle.

    The clinical benefit of DBS is largely dependent on the spatial distribution of the electric field in relation to brain anatomy. To maximize therapeutic benefits while avoiding unwanted side-effects, knowledge of the distribution of the electric field in relation anatomy is essential. Due to difficulties in measuring electric fields in vivo, computerized analysis with finite element models have emerged as an alternative.

    The aim of the thesis was to investigate technical and clinical aspects of DBS by means of finite element models, simulations, and visualizations of the electric field and tissue anatomy. More specifically the effects of dilated perivascular spaces filled with cerebrospinal fluid on the electrical field generated by DBS was evaluated. A method for patient-specific finite element modelling and simulation of DBS was developed and used to investigate the anatomical distribution of the electric field in relation to clinical effects and side effects. Patient-specific models were later used to investigate the electric field in relation to effects on speech and movement during DBS in patients with PD (n=10). Patient-specific models and simulations were also used to evaluate the influence of heterogeneous isotropic and heterogeneous anisotropic tissue on the electric field during DBS. In addition, methods were developed for visualization of atlas-based and patient-specific anatomy in 3D for interpretation of anatomy, visualization of neural activation with the activating function, and visualization of tissue micro structure. 3D visualization of anatomy was used to assess electrode contact locations in relation to stimulation-induced side-effects (n=331) during DBS for patients with essential tremor (n=28). The modelling, simulation, and visualization of DBS provided detailed information about the distribution of the electric field and its connection to clinical effects and side-effects of stimulation. In conclusion, the results of this thesis provided insights that may help to improve DBS as a treatment for movement disorders as well as for other neurological diseases in the future.

    List of papers
    1. The effect of cystic cavities on deep brain stimulation in the basal ganglia: A simulation-based study
    Open this publication in new window or tab >>The effect of cystic cavities on deep brain stimulation in the basal ganglia: A simulation-based study
    Show others...
    2006 (English)In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 3, no 2, 132-138 p.Article in journal (Refereed) Published
    Abstract [en]

    Although the therapeutic effect of deep brain stimulation (DBS) is well recognized, a fundamental understanding of the mechanisms responsible is still not known. In this study finite element method (FEM) modelling and simulation was used in order to study relative changes of the electrical field extension surrounding a monopolar DBS electrode positioned in grey matter. Due to the frequently appearing cystic cavities in the DBS-target globus pallidus internus, a nucleus of grey matter with and without a cerebrospinal fluid filled cystic cavity was modelled. The position, size and shape of the cyst were altered in relation to the electrode. The simulations demonstrated an electrical field around the active element with decreasing values in the radial direction. A stepwise change was present at the edge between grey and white matters. The cyst increased the radial extension and changed the shape of the electrical field substantially. The position, size and shape of the cyst were the main influencing factors. We suggest that cystic cavities in the DBS-target may result in closely related unexpected structures or neural fibre bundles being stimulated and could be one of the reasons for suboptimal clinical effects or stimulation-induced side effects. © 2006 IOP Publishing Ltd.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2006
    National Category
    Biomedical Laboratory Science/Technology
    Identifiers
    urn:nbn:se:liu:diva-34125 (URN)10.1088/1741-2560/3/2/007 (DOI)000239673500007 ()16705269 (PubMedID)2-s2.0-33744911364 (Scopus ID)20869 (Local ID)20869 (Archive number)20869 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    2. Method for patient-specific finite element modeling and simulation of deep brain stimulation
    Open this publication in new window or tab >>Method for patient-specific finite element modeling and simulation of deep brain stimulation
    Show others...
    2009 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 47, no 1, 21-28 p.Article in journal (Refereed) Published
    Abstract [en]

    Deep brain stimulation (DBS) is an established treatment for Parkinsons disease. Success of DBS is highly dependent on electrode location and electrical parameter settings. The aim of this study was to develop a general method for setting up patient-specific 3D computer models of DBS, based on magnetic resonance images, and to demonstrate the use of such models for assessing the position of the electrode contacts and the distribution of the electric field in relation to individual patient anatomy. A software tool was developed for creating finite element DBS-models. The electric field generated by DBS was simulated in one patient and the result was visualized with isolevels and glyphs. The result was evaluated and it corresponded well with reported effects and side effects of stimulation. It was demonstrated that patient-specific finite element models and simulations of DBS can be useful for increasing the understanding of the clinical outcome of DBS.

    Place, publisher, year, edition, pages
    Springer, 2009
    Keyword
    Deep brain stimulation, Patient-specific, Simulation, Finite element, Glyph
    National Category
    Biomedical Laboratory Science/Technology
    Identifiers
    urn:nbn:se:liu:diva-16616 (URN)10.1007/s11517-008-0411-2 (DOI)000262483600004 ()18936999 (PubMedID)2-s2.0-58649107661 (Scopus ID)
    Note

    The original publication is available at www.springerlink.com: Mattias Åström, Ludvic U Zrinzo, Stephen Tisch, Elina Tripoliti, Marwan I Hariz and Karin Wårdell , Method for patient-specific finite element modeling and simulation of deep brain stimulation, 2009, Medical and Biological Engineering and Computing, (47), 1, 21-28. http://dx.doi.org/10.1007/s11517-008-0411-2 Copyright: Springer Science Business Media http://www.springerlink.com/

    Available from: 2009-02-07 Created: 2009-02-06 Last updated: 2017-12-14Bibliographically approved
    3. Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation
    Open this publication in new window or tab >>Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation
    Show others...
    2010 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 88, no 4, 224-233 p.Article in journal (Refereed) Published
    Abstract [en]

    Background/Aims: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson’s disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. Methods: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. Results: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. Conclusion: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.

    Keyword
    Deep brain stimulation, Dysarthria, Speech intelligibility, Parkinson’s disease, Electric field, Fasciculus cerebellothalamicus
    National Category
    Biomedical Laboratory Science/Technology
    Identifiers
    urn:nbn:se:liu:diva-58057 (URN)10.1159/000314357 (DOI)000280136100004 ()
    Note

    Original Publication: Mattias Åström, Elina Tripoliti, Mawan I. Hariz, Ludvig U. Zrinzo, Irene Martinez-Torres, Patricia Limousin and Karin Wårdell, Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation, 2010, Stereotactic and Functional Neurosurgery, (88), 4, 224-233. http://dx.doi.org/10.1159/000314357 Copyright: S. Karger AG http://www.karger.com/

    Available from: 2010-07-27 Created: 2010-07-27 Last updated: 2017-12-12Bibliographically approved
    4. Influence of heterogeneous and anisotropic tissue conductivity on electric field distribution in deep brain stimulation
    Open this publication in new window or tab >>Influence of heterogeneous and anisotropic tissue conductivity on electric field distribution in deep brain stimulation
    2012 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 50, no 1, 23-32 p.Article in journal (Refereed) Published
    Abstract [en]

    The aim was to quantify the influence of heterogeneous isotropic and heterogeneous anisotropic tissue on the spatial distribution of the electric field during deep brain stimulation (DBS). Three finite element tissue models were created of one patient treated with DBS. Tissue conductivity was modelled as I) homogeneous isotropic, II) heterogeneous isotropic based on MRI, and III) heterogeneous anisotropic based on diffusion tensor MRI. Modelled DBS electrodes were positioned in the subthalamic area, the pallidum, and the internal capsule in each tissue model. Electric fields generated during DBS were simulated for each model and target-combination and visualized in 3D with isolevels at 0.20 (inner), and 0.05 V m-1 (outer). F-test and vector analysis was used for statistical evaluation of the distribution of the electric field. Heterogeneous isotropic tissue altered the spatial distribution of the electric field by up to 4% at inner, and up to 10% at outer isolevel. Heterogeneous anisotropic tissue had a larger impact on the distribution of the electric field with an influence of up to 18% and 15% at each isolevel, respectively. The influence of heterogeneous and anisotropic tissue on the electric field may be clinically relevant in anatomic regions that are functionally subdivided and surrounded by multiple fibres of passage.

    Place, publisher, year, edition, pages
    Springer, 2012
    Keyword
    Deep brain stimulation, Diffusion tensor, Finite element, Model, Simulation, Patient-specific
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-70087 (URN)10.1007/s11517-011-0842-z (DOI)000298648400003 ()
    Note

    funding agencies|Swedish Foundation for Strategic Research (SSF)||Swedish Research Council (VR)| 621-2008-3013 |Swedish Governmental Agency for Innovation Systems (VINNOVA)| 311-2006-7661 |

    Available from: 2011-08-18 Created: 2011-08-18 Last updated: 2017-12-08Bibliographically approved
    5. Stimulation-induced side effects in the posterior subthalamic area: distribution, characteristics and visualization
    Open this publication in new window or tab >>Stimulation-induced side effects in the posterior subthalamic area: distribution, characteristics and visualization
    2013 (English)In: Clinical neurology and neurosurgery (Dutch-Flemish ed. Print), ISSN 0303-8467, E-ISSN 1872-6968, Vol. 15, no 1, 65-71 p.Article in journal (Refereed) Published
    Abstract [en]

    Objective: The posterior subthalamic area (PSA) is an emerging but relatively unexplored target for DBS treatment of tremor. The aim of the study was to explore the area further by evaluating the spatial distribution and the characteristics of stimulation-induced side effects in this area. Methods: Twenty-eight patients with essential tremor (ET) implanted with 33 DBS electrodes were evaluated concerning stimulation-induced side effects by testing each contact separately one year after surgery. The location of the side effects were plotted on axial slides of the Morel Stereotactic Atlas and a 3-dimensional model of the area for visualization was created. Results: Visualization of the contacts eliciting stimulation-induced side effects demonstrated that identical responses can be elicited from various points in the PSA and its vicinity. The majority of contacts inducing muscular affection and cerebellar symptoms, including dysarthria, could not be attributed to an effect on the internal capsule. Paresthesias, affecting various body parts were elicited throughout the area without a clear somatotopic pattern. Conclusion: Stimulation-induced side effects in the PSA and its vicinity are difficult to attribute to certain anatomical areas as the same response can be induced from various locations, and are thus of limited localizing value.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-70088 (URN)10.1016/j.clineuro.2012.04.015 (DOI)000312576300012 ()
    Available from: 2011-08-18 Created: 2011-08-18 Last updated: 2017-12-08Bibliographically approved
  • 25.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Sapiens Steering Brain Stimulation B.V., The Netherlands .
    Neuronmodeling and DBS electric field simulations2014Conference paper (Other academic)
  • 26.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology. Sapiens Steering Brain Stimulation BV, NL-5656 Eindhoven, Netherlands.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Martens, Hubert
    Sapiens Steering Brain Stimulation B.V., Eindhoven, The Netherlands.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Relationship between Neural Activation and Electric Field Distribution during Deep Brain Stimulation2015In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 62, no 2, 664-72 p.Article in journal (Refereed)
    Abstract [en]

    Models and simulations are commonly used to study deep brain stimulation (DBS). Simulated stimulation fields are often defined and visualized by electric field isolevels or volumes of tissue activated (VTA). The aim of the present study was to evaluate the relationship between stimulation field strength as defined by the electric potential V, the electric field E, and the divergence of the electric field ∇(2) V, and neural activation. Axon cable models were developed and coupled to finite-element DBS models in three-dimensional (3-D). Field thresholds ( VT , ET, and ∇(2) VT ) were derived at the location of activation for various stimulation amplitudes (1 to 5 V), pulse widths (30 to 120 μs), and axon diameters (2.0 to 7.5 μm). Results showed that thresholds for VT and ∇(2) VT were highly dependent on the stimulation amplitude while ET were approximately independent of the amplitude for large axons. The activation field strength thresholds presented in this study may be used in future studies to approximate the VTA during model-based investigations of DBS without the need of computational axon models.

  • 27.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Computational analysis of the electric field during deep brain stimulation (oral, invited)2010Conference paper (Refereed)
  • 28.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Diczfalusy, Elin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Software for patient-specific modeling and simulation of deep brain stimulation (poster)2011Conference paper (Other academic)
  • 29.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Johansson, Johannes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Hariz, Marwan
    Institute of Neurology London.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    The effect of cystic cavities on deep brain stimulation in the basal ganglia: A simulation-based study2006In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 3, no 2, 132-138 p.Article in journal (Refereed)
    Abstract [en]

    Although the therapeutic effect of deep brain stimulation (DBS) is well recognized, a fundamental understanding of the mechanisms responsible is still not known. In this study finite element method (FEM) modelling and simulation was used in order to study relative changes of the electrical field extension surrounding a monopolar DBS electrode positioned in grey matter. Due to the frequently appearing cystic cavities in the DBS-target globus pallidus internus, a nucleus of grey matter with and without a cerebrospinal fluid filled cystic cavity was modelled. The position, size and shape of the cyst were altered in relation to the electrode. The simulations demonstrated an electrical field around the active element with decreasing values in the radial direction. A stepwise change was present at the edge between grey and white matters. The cyst increased the radial extension and changed the shape of the electrical field substantially. The position, size and shape of the cyst were the main influencing factors. We suggest that cystic cavities in the DBS-target may result in closely related unexpected structures or neural fibre bundles being stimulated and could be one of the reasons for suboptimal clinical effects or stimulation-induced side effects. © 2006 IOP Publishing Ltd.

  • 30.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Johansson, Johannes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Modeling and simulation of electric fields generated by brain stimulation electrodes: the effect of cystic cavities in the basal ganglia2005In: Proceedings from the International IEEE EMBS Conference on Neural Engineering, IEEE , 2005, 198-201 p.Conference paper (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is an effective method for managing movement disorders. A small electrode is implanted in the basal ganglia and an electric potential is applied to one or more active elements of the electrode in order to simulate the neurons in the surrounding tissue. The fundamental understanding of the mechanisms responsible for the therapeutic DBS effects is unknown. A method to increase the knowledge is to use computer simulations. In this study the finite element method has been used for investigation of relative changes of the electrical field extension surrounding a monopolar DBS-electrode positioned in gray matter. Due to the frequently appearing cystic cavities in globus pallidus and putamen a nucleus of gray matter with and without a cerebrospinal fluid filled cystic cavity was modeled. The simulations demonstrated an electrical field around the active element with decreasing values in the radial direction. A stepwise change was present at the edge between gray and white matter. The cyst increased the radial extension and changed the shape of the field. This may result in closely related unexpected structures being stimulated and could be one of the reasons of reported postoperative complications.

  • 31.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Lemair, Jean-Jaques
    Hôpital Gabriel Montpied, Service de Neurochirurgie, Clermont-Ferrand, France.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    The influence of brain tissue heterogeneity and anisotropy on deep brain stimulation in the subhalamic nucleus2009Conference paper (Refereed)
  • 32.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Lemaire, Jean-Jacques
    Clermont Université, Université d'Auvergne, EA 3295, Equipe de recherche en signal et imagerie médicale, Image- Guided Clinical Neuroscience and Connectomics (IGCNC), BP 10448, F-63000 Clermont-Ferrand, France/CHU Clermont-Ferrand, Service de Neurochirurgie, F-63003 Clermont-Ferrand, France.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Influence of heterogeneous and anisotropic tissue conductivity on electric field distribution in deep brain stimulation2012In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 50, no 1, 23-32 p.Article in journal (Refereed)
    Abstract [en]

    The aim was to quantify the influence of heterogeneous isotropic and heterogeneous anisotropic tissue on the spatial distribution of the electric field during deep brain stimulation (DBS). Three finite element tissue models were created of one patient treated with DBS. Tissue conductivity was modelled as I) homogeneous isotropic, II) heterogeneous isotropic based on MRI, and III) heterogeneous anisotropic based on diffusion tensor MRI. Modelled DBS electrodes were positioned in the subthalamic area, the pallidum, and the internal capsule in each tissue model. Electric fields generated during DBS were simulated for each model and target-combination and visualized in 3D with isolevels at 0.20 (inner), and 0.05 V m-1 (outer). F-test and vector analysis was used for statistical evaluation of the distribution of the electric field. Heterogeneous isotropic tissue altered the spatial distribution of the electric field by up to 4% at inner, and up to 10% at outer isolevel. Heterogeneous anisotropic tissue had a larger impact on the distribution of the electric field with an influence of up to 18% and 15% at each isolevel, respectively. The influence of heterogeneous and anisotropic tissue on the electric field may be clinically relevant in anatomic regions that are functionally subdivided and surrounded by multiple fibres of passage.

  • 33.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tisch, Stephen
    Institute of Neurology University College, London, UK.
    Zrinzo, Ludvic U.
    Institute of Neurology University College, London, UK.
    Tripoliti, Elina
    University of Neurology University College, London, UK.
    Hariz, Marwan I.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    A model-Based analysis of deep brain stimulation2007Conference paper (Other academic)
    Abstract [en]

      

  • 34.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Tripoliti, E
    n/a.
    Hariz, M I
    n/a.
    Zrinzo, L U
    n/a.
    Martinez-Torre, I
    n/a.
    Limousin, P
    n/a.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Swedish Movement Disorder Society, Umeå 15-16 october, 20092009In: The electric field during DBS, 2009Conference paper (Other academic)
  • 35.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tripoliti, E.
    Institute of Neurology University College London.
    Zrinzo, U.
    Institute of Neurology University College London.
    Marinez-Torres, I.
    Institute of Neurology University College London.
    Limousin, P.
    Institute of Neurology University College London.
    Hariz, M. I.
    Institute of Neurology University College London.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Voltage steering to control deep brain stimulation-induced speech deficits2008In: XVIII Congress of the European Society for Stereotactic and Functional Neurosurgery,2008, 2008Conference paper (Other academic)
  • 36.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Tripoliti, Elina
    University College, London.
    Hariz, Mawan I.
    University Hospital, Umeå .
    Zrinzo, Ludvig U.
    University College, London.
    Martinez-Torres, Irene
    University College, London.
    Limousin, Patricia
    University College, London.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation2010In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 88, no 4, 224-233 p.Article in journal (Refereed)
    Abstract [en]

    Background/Aims: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson’s disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. Methods: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. Results: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. Conclusion: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.

  • 37.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Tripoliti, Elina
    Institute of Neurology, Queen Square, University College London, UK.
    Martinez-Torres, Irene
    Institute of Neurology, Queen Square, University College London, UK.
    Zrinzo, Ludvic U.
    Institute of Neurology, Queen Square, University College London, UK.
    Limousin, Patricia
    Institute of Neurology, Queen Square, University College London, UK.
    Hariz, Marwan I.
    Institute of Neurology, Queen Square, University College London, UK; Dept of Neurosurgery, University Hospital, Umeå, Sweden.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Patient-specific models and simulations of deep brain stimulation for postoperative follow-up2009In: World Congress on Medical Physics and Biomedical Engineering / [ed] Olaf Dössel and Wolfgang C. Schlegel, Springer , 2009, 331-334 p.Conference paper (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is an established treatment for Parkinson’s disease (PD). The success of DBS is highly dependent on electrode location and electrical parameter settings. In this study patient-specific computer models of DBS were used for postoperative follow-up in three PD patients who suffered from stimulation induced hypomania, dysarthria, and uncontrollable laughter respectively. The overall aim of the study was to relate the anatomical aspect of the electric field to the effects and side effects of stimulation. The simulations showed the anatomical distribution of the electric field for all the patients and the results were in agreement with previous reports regarding these side effects of stimulation. It was demonstrated that patient-specific models and simulations of DBS may be useful for postoperative follow-up of DBS.

  • 38.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tripoliti, Elina
    Institute of Neurology University College London, UK.
    Zrinzo, Ludvic U.
    Institute of Neurology University College London, UK.
    Martinez-Torres, Irene
    Institute of Neurology University College London, UK.
    Limousin, Patricia
    Institute of Neurology University College London, UK.
    Hariz, Marwan I.
    Institute of Neurology University College London, UK.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Voltage steering to control the effects and side effects of deep brain stimulation2008Conference paper (Other academic)
  • 39.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tripoliti, Elina
    Institute of Neurology University College, London, UK.
    Zrinzo, Ludvic U
    Institute of Neuroligy University College, London, UK.
    Tisch, Stephen
    Institute of Neurology University College, London, UK.
    Martinez-Torres, Irene
    Institute of Neurology University College, London, UK.
    Limousin, Patricia
    Institute of Neurology University College, London, UK.
    Hariz, Marwan I.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Effects of bilateral subthalamic nucleus deep brain stimulation on speech intelligibillity and movement: A model-based case stydy.2007In: XVII WFN World Congress on Parkinson´s disease and related disorders,2007, 2007Conference paper (Other academic)
    Abstract [en]

      

  • 40.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    U. Zrinzo, Ludvic
    Institute of Neurology, Queen Square, London, UK.
    I. Hariz, Marwan
    Inst. för Neurokirurgi Norrlands universitetssjukhus, Umeå samt Institute of Neurology, Queen Square, London, UK.
    Tisch, Stephen
    Institute of Neurology, Queen Square, London, UK.
    Limousin, Patricia
    Institute of Neurology, Queen Square, London, UK.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Patientspecifik modellering och simulering av djup hjärnstimulering2006In: Medicinteknikdagarna 2006,2006, 2006Conference paper (Other academic)
  • 41.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Zrinzo, L.U.
    Institute of Neurology Queen square, London, UK.
    Hariz, Marwan
    Institute of Neurology Queen square, London, UK.
    Tisch, Stephen
    Institute of Neurology Queen Square, London, UK.
    Limousin, Patricia
    Institute of Neurology Queens Square, London, UK.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Patient specific modelling and simulation of deep brain stimulation: A method for pre- and postoperative investigations2006Conference paper (Other academic)
  • 42.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Zrinzo, Ludvic U
    University College London.
    Tisch, Stephen
    Linköping University, The Institute of Technology.
    Tripoliti, Elina
    University College London.
    Hariz, Marwan I
    University College London.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Method for patient-specific finite element modeling and simulation of deep brain stimulation2009In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 47, no 1, 21-28 p.Article in journal (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is an established treatment for Parkinsons disease. Success of DBS is highly dependent on electrode location and electrical parameter settings. The aim of this study was to develop a general method for setting up patient-specific 3D computer models of DBS, based on magnetic resonance images, and to demonstrate the use of such models for assessing the position of the electrode contacts and the distribution of the electric field in relation to individual patient anatomy. A software tool was developed for creating finite element DBS-models. The electric field generated by DBS was simulated in one patient and the result was visualized with isolevels and glyphs. The result was evaluated and it corresponded well with reported effects and side effects of stimulation. It was demonstrated that patient-specific finite element models and simulations of DBS can be useful for increasing the understanding of the clinical outcome of DBS.

1 - 42 of 42
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