Elena Najdenovska

Deep brain stimulation after previous gamma knife thalamotomy of the Vim for essential tremor is feasible! Clinical, electrophysiological and radiological findings

Reference EPFL-ARTICLE-229525doi:10.1007/s00701-017-3227-8View record in Web of Science Record created on 2017-07-10, modified on 2017-07-10

Visually-sensitive networks in essential tremor: evidence from structural and functional imaging

1 Centre Hospitalier Universitaire Vaudois (CHUV), Neurosurgery Service and Gamma Knife Center, Lausanne, Switzerland 2 Medical Image Analysis Laboratory (MIAL) and Department of Radiology-Center of Biomedical Imaging (CIBM), Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland 3 Signal Processing Laboratory (LTS 5), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland 4 University of Lausanne, Faculty of Biology and Medicine, Lausanne, Switzerland 5 Stereotactic and Functional Neurosurgery Service and Gamma Knife Unit, CHU Timone, Marseille, France 6 Neurology Department, CHU Timone, Marseille, France 7 AMU, CRMBM UMR CNRS 7339, Faculté de Médecine and APHM, Hopital Timone, Department of Diagnostic and Interventionnal Neuroradiology, Marseille, France 8 Centre Hospitalier Universitaire Vaudois, Department of Radiology, Lausanne, Switzerland 9 University of Geneva, Faculty of Medicine, Switzerland 10 Medical Image Processing Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Pretherapeutic functional neuroimaging predicts tremor arrest after thalamotomy

Essential tremor (ET) represents the most common movement disorder. Drug‐resistant ET can benefit from standard stereotactic procedures (deep brain stimulation or radiofrequency thalamotomy) or alternatively minimally invasive high‐focused ultrasound or radiosurgery. All aim at same target, thalamic ventro‐intermediate nucleus (Vim).

S180. MICROSTRUCTURE COMPLEXITY OF THE THALAMUS IN SCHIZOPHRENIA: A NODDI STUDY

Abstract Background Schizophrenia is a neurodevelopmental disease arising from complex interactions between genetic and environmental factors that cause disconnectivity within core brain networks including the thalamus. The thalamus has a central role in the pathophysiology of schizophrenia, however to what extent and how it is affected at the microstructural level is still a matter of debate. In the current study, we apply the Neurite Orientation Dispersion and Density Imaging (NODDI) [1], a recently developed MRI technique, which allows the estimation of the microstructural complexity of dendrites and axons in vivo. Methods Twenty-three patients with schizophrenia (SCHZ) were recruited from the Service of General Psychiatry (Lausanne University Hospital, Switzerland) (40.18 ± 9.2yo; 18/5 males/females) and 27 healthy controls (HC) (37.7 ± 7.95yo; 18/9 males/females). Magnetization-Prepared Rapid Acquisition Gradient Echo (MPRAGE) and a diffusion spectrum imaging (DSI) was performed on a 3-Tesla scanner (MAGNETOM Trio a Tim system, Siemens, Germany). Thalamus segmentation was performed on the MPRAGE sequence with an in house-pipeline using Freesurfer v5.0.0 for segmentation which was then refined to remove voxels within the ventricles and/or overlapping the internal capsule [2]. Orientation Dispersion Index (ODI), Intracellular Volume Fraction (ICVF) and, Isotropic Volume Fraction (ISOVF) were estimated based on the DSI sequence with NODDI [1]. General Linear Models (GLM) were estimated with outcome measures (ICVF, ISOVF, ODI) as dependent variables, group membership as a fixed factor (HC vs. SCHZ) and age and gender as potential covariates. References 1Battistella G, Najdenovska E, Maeder P, et al. Robust thalamic nuclei segmentation method based on local diffusion magnetic resonance properties. Brain Struct Funct 2016. DOI:10.1007/s00429-016-1336-4. 2Zhang H, Schneider T, Wheeler-kingshott CA, Alexander DC. NeuroImage NODDI : Practical in vivo neurite orientation dispersion and density imaging of the human brain. Neuroimage 2012; 61: 1000–16. Results Mean ODI was significantly increased in schizophrenia patients compared to controls in the right thalamus (F(1,48)=5.032, p= .030, np2 = .095) and in the left thalamus (F(1,48)=4.500, p= .039, np2 = .086). When controlled for age and gender, the difference remained significant for the right thalamus (F(1, 46) = 4.197, p = .046, np2 = .084) but reduced to trend level for the left thalamus (F(1, 46) = 4.029, p = .051, np2 = .081). There were no significant differences on the other measures (ICVF, ISOVF). Discussion Our results show that the thalamus is affected in patients with SCHZ at the microstructural level. The observed increase in ODI, which estimates the dispersion of neurite orientations, suggests disrupted neurite organization in patients as compared to HC.

Towards an Automated Segmentation of the Ventro-Intermediate Thalamic Nucleus

The ventro-intermediate nucleus (Vim), as the others thalamic subparts, cannot be directly visualized by current standard magnetic resonance imaging (MRI), in daily clinical practice. Hence, for treatment of tremor in functional neurosurgery, where the commonly used target is the Vim, the targeting procedure is done indirectly. We present a novel direct automated segmentation of the Vim using only subject-related MRI information, specifically, diffusion MRI at 3T and susceptibility weighted images (SWI) acquired at 7T. With a state-of-the-art method based on local diffusion MR properties for automated subdivision of the thalamus, we first restrain the region of interest to the group of motor-related nuclei. Then, this thalamic part is further subdivided, in graph parcellation manner, using the intensity-related features provided by SWI together with prior knowledge of the Vim localization inside the motor thalamic segment. Our framework was tested in four healthy elderly subjects, for eight thalami in total, and the results were evaluated by an experienced neurosurgeon, showing the ability to directly detect the Vim area. The qualitative inspection indicated that the proposed method outperforms standard multi-atlas based techniques.