The report by Enzinger et al1 confirms the earlier study by Chapman et al2 regarding the predictive value of the apolipoprotein E ϵ4 allele (APOE ϵ4) for severity in multiple sclerosis. Reduced N-acetylaspartate levels have been shown to be valuable markers for cognitive decline in several diseases, including Alzheimer disease3,4 and multiple sclerosis5 (C. Christodoulou, PhD, L. B. Krupp, MD, Z. Liang, PhD, et al, written communication, 2003). Were any data collected by Enzinger and colleagues on cognitive function in their various patient subgroups, with attempts to correlate cognitive decline to APOE ϵ4 allele and N-acetylaspartate levels?