Sharmilee Gnanapavan

Background and purpose Neurofilament light chain (NfL) is an accepted biomarker of disease activity in multiple sclerosis (MS), but its relationship with magnetic resonance imaging (MRI) activity particularly in reference to lesion location and recurrent activity is not well understood. Methods In 139 MS patients who underwent lumbar punctures with follow‐up in 25, the relationship between cerebrospinal fluid (CSF) NfL and cranial MRI based on lesion location and lesion number was evaluated. Spearman rank correlation was used to assess the association between CSF NfL and MRI lesion location and lesion counts at baseline and follow‐up at 1 year. Multiple linear regression analysis was performed to assess which lesion location was most strongly associated with CSF NfL values. Results The associations between baseline CSF NfL and lesion location and follow‐up lesions were modest, whilst those between baseline MRI and follow‐up CSF NfL were greater: periventricular ( r = 0.31, p = 0.141), juxtacortical ( r = 0.47, p = 0.022), infratentorial ( r = 0.71, p ≤ 0.001) and cord lesions ( r = 0.60, p = 0.002). All associations, however, improved following adjustment for disease duration and type of MS. Modelling revealed 53% of (log) CSF NfL could be explained by variance in baseline MRI lesion location. Conclusions Baseline CSF NfL did not correlate with current or future MRI activity and lesion location. However, baseline MRI activity explained around 53% of the variation in the follow‐up CSF NfL, suggesting that the relationship between MRI and CSF NfL is mainly precedent rather than an association, that is one occurring before the other.