Regional hippocampal vulnerability in early multiple sclerosis: Dynamic pathological spreading from dentate gyrus to CA1

Background Whether hippocampal subfields are differentially vulnerable at the earliest stages of multiple sclerosis (MS) and how this impacts memory performance is a current topic of debate. Method We prospectively included 56 persons with clinically isolated syndrome (CIS) suggestive of MS in a 1‐year longitudinal study, together with 55 matched healthy controls at baseline. Participants were tested for memory performance and scanned with 3 T MRI to assess the volume of 5 distinct hippocampal subfields using automatic segmentation techniques. Results At baseline, CA4/dentate gyrus was the only hippocampal subfield with a volume significantly smaller than controls (p