Section: New Results

Clinical and Neurocognitive Applications of Diffusion MRI

Brain correlates of apathy in Kleine Levin syndrome: a mean apparent propagator study

Participants : Anne-Charlotte Philippe [ICM, CENIR, Paris] , Sophie Lavault [ICM, CENIR, Paris] , Rutger Fick, Demian Wassermann, Romain Valabregue [ICM, CENIR, Paris] , Richard Levy [ICM, CENIR, Paris] , Isabelle Arnulf [ICM, CENIR, Paris] , Stéphane Lehericy [ICM, CENIR, Paris] , Rachid Deriche.

Kleine-Levin syndrome (KLS) is a rare neurological disorder characterized by episodes of severe hypersomnia, apathy, cognitive impairment, derealization and behavioral disturbances. Between episodes, patients have normal sleep, mood and behavior. Apathy is a prominent clinical feature of KLS but its pathophysiology is not known. Here we used mean apparent propagator to investigate white matter changes in KLS and correlated diffusion changes with apathy scores. Results showed that the corpus callosum was involved in KLS during episodes and mean RTAP measures in the corpus callosum correlated with apathy scores. Results were in accordance with known motivation-based circuits involving the orbitomedial frontal cortex.

This work has been submitted to ISMRM'2017.

Comparison of Biomarkers in Transgenic Alzheimer Rats Using Multi-shell Diffusion MRI

Participants : Rutger Fick, Madelaine Daianu [Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, USC, USA] , Marco Pizzolato, Demian Wassermann, Russel Jacobs [Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, USC, USA] , Paul Thompson [Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, USC, USA] , Terrence Town [Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, USC, USA] , Rachid Deriche.

In this study, we assessed the evolution of diffusion MRI (dMRI) derived markers from different white matter models as progressive neurodegeneration occurs in transgenic Alzheimer rats (TgF344-AD) at 10, 15 and 24 months. We compared biomarkers reconstructed from Diffusion Tensor Imaging (DTI), Neurite Orientation Dispersion and Density Imaging (NODDI) and Mean Apparent Propagator (MAP)-MRI in the hippocampus, cingulate cortex and corpus callosum using multi-shell dMRI. We found that NODDI's dispersion and MAP-MRI's anisotropy markers consistently changed over time, possibly indicating that these measures are sensitive to age-dependent neuronal demise due to amyloid accumulation. Conversely, we found that DTI's mean diffusivity, NODDI's isotropic volume fraction and MAP-MRI's restriction-related metrics all followed a two-step progression from 10 to 15 months, and from 15 to 24 months. This two-step pattern might be linked with a neuroinflammatory response that may be occuring prior to, or during microstructural breakdown. Using our approach, we are able to provide for the first time-preliminary and valuable insight on relevant biomarkers that may directly describe the underlying pathophysiology in Alzheimer's disease.

This work has been published in  [30].