Basal ganglia and thalamus in Parkinson disease: structural and connectivity associated changes

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1 Basal ganglia and thalamus in Parkinson disease: structural and connectivity associated changes Poster No.: C-0851 Congress: ECR 2014 Type: Authors: Keywords: DOI: Scientific Exhibit M. Onu, L. Badea, A. Roceanu; Bucharest/RO Tissue characterisation, Computer Applications-Detection, diagnosis, Neural networks, MR-Functional imaging, MR, Neuroradiology brain, Computer applications /ecr2014/C-0851 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 6

2 Aims and objectives We hypothesized that, in Parkinson disease (PD), gray matter density and functional cerebral connectivity might develop compensatory behaviors in response to the damaged motor control loops (the basal ganglia-thalamocortical circuit (BTC) and cerebellothalamocortical circuit (CTC)), especially at the basal ganglia/thalamic level. Methods and materials Fourteen PD patients and 9 age and sex matched healthy volunteers were investigated with a 1.5 T MRI system. MPRAGE sequence for gray matter structural data and Echo Planar sequence for resting state fmri. Regional gray matter changes were analyzed with an operator independent technique - Voxel-Based Morphometry (VBM). VBM involves a voxel-wise comparison of the local concentration of gray matter between two groups of subjects. Resting state acquisitions were further analysed with FSL-Melodic and, eventually, we used FSL-Dual regression to run a group-comparison ICA (Independent Component Analysis). Results Group comparison Voxel-based-morphometry (VBM) revealed increased gray matter density in right thalamus (figure 1) (p<0.02, uncorrected for multiple comparisons). Resting state fmri Dual regression performed on Basal ganglia network obtained by ICA, showed marked increased connectivity at the level of the right thalamus (figures 2,3) (p<0.02, corrected for multiple comparisons). Images for this section: Page 2 of 6

3 Fig. 1: VBM results: increased gray matter density (red-yellow) was found in the right thalamic area (standard space). Page 3 of 6

4 Fig. 2: Dual regression performed for Basal ganglia network (ICA) show increased connectivity (red-yellow) in areas involving right thalamus (Z=27) Page 4 of 6

5 Fig. 3: Dual regression performed for Basal ganglia network (ICA) show increased connectivity (red-yellow) in areas involving right thalamus (Z=26) Page 5 of 6

6 Conclusion Conventional literature has consistently demonstrated how the thalamus receives inhibitory inputs from the GPi (internal part of globus pallidus) and the SN (substantia nigra), and then projects excitatory output to the cortex. In line with the BTC loop, the inhibitory signal from the GPi and SN is weaker in PD patients as compared to healthy controls. Over the long run, therefore, thalamus enlargement may occur due to a decreased inhibitory signal 1,2. Our study brings new proofs for thalamic enlargement. The increases in gray matter density might reveal compensatory effects or self-reorganization. We hypothesized that the structural changes were associated with functional changes. Previous studies using (F 18 dopa) PET showed a regional hypermetabolism in the thalamus in PD patients 3. We used resting state fmri to investigate potential hyperconnectivity at the basal ganglia/thalamic level: no decrease connectivity were found for PD patients compared to healthy volunteers, on the contrary, an increased connectivity was detected at the level of the right thalamic area. Thalamic increased volume might be due to enhanced thalamo-motorcortical interaction which is known to be present in PD. The increased connectivity at thalamic level in PD patients compared to healthy volunteers seems to confirm this hypothesis. Personal information References 1. Lin C-H et al. VBM reveals brain volume differences between Parkinson's disease and essential tremor patients. Front Hum Neurosci. 2013;7: Kassubek, J. et al., Thalamic gray matter changes in unilateral Parkinsonian restingtremor: a voxel-based morphometric analysis of 3 dimensionalmagnetic resonance imaging, Neuroscience Letters 323 (2002) Kassubek, J.et al., Hypermetabolism in theventrolateral thalamus in unilateral Parkinsonian restingtremor: a positron emission tomography study, Neurosci.Lett., 304 (2001) Page 6 of 6