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Scientific result | Medical imaging | MRI

Imaging of bipolar disorder and NODDI model: new light on the action of lithium.

​A collaboration involving NeuroSpin sheds new light on the action of lithium in bipolar disorder. The modeling (NODDI) of water diffusion measured by diffusion MRI allowed analysis of cerebral microstructure. Results indicate increased dendritic density in the frontal cortex of lithium-treated patients. This suggests that an improved communication between neurons in this region of the brain may underlie the beneficial effects of lithium in bipolar disorder.

Published on 9 April 2019

MRI studies in patients with bipolar disorder have suggested that lithium is associated with grey matter increases that may underlie its therapeutic effects. However, the relationship between grey matter volume and cellular microstructural changes is not straightforward, as modifications of different cellular compartments of grey matter may be involved.

Our aim was to test the hypothesis that dendritic density is higher in patients undergoing lithium therapy than in patients without lithium, using advanced modelling of water diffusion investigated with MRI.

We included 41 patients and 40 controls matched for age and gender from two sites. All subjects underwent 3T MRI with 3 shells of diffusion. We used neurite orientation dispersion and density imaging to compare the grey matter neurite density between patients undergoing lithium therapy or not and control subjects.

We found a significant group effect in the left prefrontal region (p = 0.001, Bonferroni corrected): patients without lithium had a lower frontal neurite density than controls (p = 0.009), while those on lithium had a higher mean neurite density than those without (p < 0.001). Patients on lithium were not different from controls (p = 0.08).

This is the first study to report in vivo evidence of preserved neurite density of the prefrontal cortex in humans associated with lithium intake. Changes of intracellular volume fraction are thought to reflect changes of grey matter microstructural organization. This reinforces the hypothesis of lithium having a positive effect on the neuronal compartment in humans.

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