We are grateful to Dr Mazurek for addressing the possibility that the greater reduction in N-acetylaspartate levels that we observed in the APOEϵ4 carriers of our multiple sclerosis cohort might correlate with worse cognitive performance in this subgroup of patients. In fact, N-acetylaspartate measurements have consistently been helpful in evaluating the extent of neuronal damage in dementia disorders. Nevertheless, data on magnetic resonance spectroscopy and cognition in multiple sclerosis are scarce.1,2 To our knowledge to date, there exists only 1 cross-sectional study of 98 patients, by Oliveri et al,3 probing the possible association of the APOE genotype with neuropsychological function in multiple sclerosis, which yielded negative results regarding the APOE polymorphism. However, evidence pointing in this direction arises from the same study via the association of the −491A/T promoter polymorphism in the regulatory region of the APOE gene with cognitive impairment. Unfortunately, our study did not include detailed neuropsychological testing to answer Dr Mazurek's question, but we plan to follow his suggestion.
Enzinger C, Fazekas F. Reduced N-acetylaspartate Levels and Cognitive Decline—Reply. Arch Neurol. 2004;61(2):296. doi:10.1001/archneur.61.2.296-b