To test whether thalamic volume at the time of relapse predicts later cognitive recovery, as compared to total lesion volume on T2/FLAIR.

Relapse in multiple sclerosis (MS) is marked by acute declines of motor, sensory, and/ or cognitive functioning. Group data from several studies show that cognitive decline during acute disease activity is followed by varying degrees of recovery. Factors associated with such recovery, including the relative roles of neurodegenerative and inflammatory processes, are yet to be examined. In particular, thalamic atrophy has previously shown a robust association with overall cognitive status in MS.

54 relapsing MS patients from three centers were imaged on 3T MRI using 3D T1 and T2/FLAIR. The Symbol Digit Modalities Test (SDMT), a measure of processing speed, was assessed at baseline, during relapse, and 3-month follow-up. FMRIB’s Integrated Registration and Segmentation Tool (FIRST) was used to calculate thalamic volume. T2 lesion volume (T2-LV) was assessed using a semiautomated contouring technique. Associations between these volumes and SDMT change were assessed via non-parametric Spearman correlations.

Group data showed SDMT decline from baseline followed by recovery at follow-up (Baseline 57.9±11.8; Relapse 54.6±12.8; Recovery 59.4±13.8). However, individual SDMT changes at follow-up ranged from -12 to 23.  Thalamic volume at relapse was related to degree of SDMT recovery (r=0.287, p=0.036). Conversely, T2-LV was not (r=-0.044, p=0.752).

Neurodegeneration, and in particular thalamic atrophy, may play a more important role in recovery from acute cognitive decline during MS relapse than overall brain lesion burden. This also suggests a meaningful role for brain reserve.