ADC restriction is not associated with clinical response to plasma exchange following a cerebral attack of multiple sclerosis

Background: MS is the most common CNS inflammatory demyelinating disease. Plasma exchange (PLEX) has well-demonstrated efficacy in acute corticosteroid-refractory attacks of demyelination but identifying the factors that predict favorable PLEX response remains elusive. We aimed to determine if apparent diffusion coefficient (ADC) restriction on brain MRI predicts clinical response to PLEX in individuals with an acute cerebral attack of MS. Methods: Retrospective chart review of individuals with a cerebral attack of MS who underwent PLEX at Mayo Clinic. Results: We identified 34 individuals who fulfilled the inclusion criteria. Twenty-seven (79%) responded to plasma exchange, with 16/34 (47%) having moderate and 11/34 (32%) marked improvement. Twenty-three (68%) people had ADC restriction on brain MRI prior to PLEX. ADC restriction did not predict response (p = 0.51). Several other pre-PLEX factors, including sex, Expanded Disability Status Scale (EDSS) at initial attack, time to PLEX, and concurrent spinal cord attack, also failed to predict response. Plasma-exchange responders had less disability at 6-month follow-up compared to non-responders (median EDSS 2.5 (range 1.0–10.0) vs. 7.5 (5.5–10.0), p<0.001). Conclusion: Acute cerebral attacks of MS have a high rate of plasma exchange response resulting in a lower EDSS at 6-months. ADC restriction does not predict response to plasma exchange.