Brain microstructural damage through serial diffusion tensor imaging and outcomes in Susac syndrome: A prospective cohort study

Abstract

Background: Susac syndrome (SuS) is a rare immune-mediated microangiopathy with potential disabling evolution. We aimed to analyze brain microstructural damage through diffusion tensor imaging (DTI) in SuS and determine its association with poor outcomes.

Method: CarESS study is a prospective multicenter national cohort study of patients with SuS. Patients included at the principal investigator's center with at least two available brain magnetic resonance imaging (MRI) with DTI were analyzed. Mean diffusivity (MD) and fractional anisotropy (FA) were measured in fibers crossing three regions of interest (ROIs): the corpus callosum as a whole, the genu of the corpus callosum, and the splenium of the corpus callosum. The primary outcome was work resumption.

Results: Twenty-two patients (36 (25;42) years, 16 (73%) females) were studied. The triad (i.e., brain, eye, and ear involvement) was complete in 21 (95%) patients. All but one patients received steroids alone or in combination with immunosuppressive drugs (n = 11) and/or IVIg (n = 7). Over a median follow-up of 6 (5;8) years, 15 (68%) patients went back to work. FA and MD were longitudinally measured in 123 DTI MRI accounting for a median of 5.6 [4.2; 7] MRI per patient. Microstructural damages in the corpus callosum as a whole, the genu of the corpus callosum, and the splenium of the corpus callosum increased during follow-up and were significantly associated with the inability to return to work.

Conclusion: Brain DTI identified microstructural damage in fibers crossing the corpus callosum that are associated with long-term disability in SuS.

Trial registration: ClinicalTrials.gov portal identifier: NCT01481662 (https://clinicaltrials.gov/ct2/show/NCT01481662?term=caress&draw=2&rank=5).

Keywords: Susac syndrome; brain microstructural damage; diffusion tensor imaging; outcome.

FIGURE 1

Brain DTI analysis. Tractography overlaid on a 3D GE T1‐weighted MRI of a normal subject, showing fibers in the brain. Due to their right–left orientation, fibers crossing the corpus callosum appear in red. The genu and splenium of the corpus callosum are indicated with solid white and hollow arrows, respectively.

FIGURE 2

Analysis of fractional anisotropy and mean diffusivity on brain DTI during follow‐up. Overtime analysis of the fractional anisotropy (FA, upper row) and the mean diffusivity (MD, lower row) in the corpus callosum (CC) as a whole, the genu, and the splenium in SuS patients according to the resumption of work (RW) status at last follow‐up. The Pearson rank correlation test was used to determine correlations between variables, with r being the Pearson correlation coefficient.