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Objectives Although many neurologists are reluctant to use natalizumab in MS (multiple sclerosis) given the increased risk for PML (progressive multifocal leukoencephalopathy), trust was regained with the introduction of JCV antibody titres as a potent disease-modifying therapy. Literature shows that in patients with a negative JCV serology, the risk of PML is virtually non-existent. Unfortunately, seroconversion causes concern amongst many neurologists. Furthermore, when patients seroconvert, it is still unclear what the risk is of passing the important threshold of 1.5. Materials & Methods JCV serology data of 161 patients were analysed, upon treatment with natalizumab at the University Hospital in Lille, France, between May 2012 and November 2014. Results Of the 81 patients who tested negative for JCV antibody at baseline, 23 (28.3%) seroconverted but only seven (8.6%) passed the threshold of 1.5. Of the 80 patients testing positive for JCV antibody at baseline, eight had an initial JCV antibody titre of 0.9 or lower of which only one of eight (12.5%) patients passed the threshold of 1.5 in the following 3 years. Eight of 15 (53.3%) patients passed this threshold if the initial serology was higher than 0.9. Conclusions JCV-negative patients and JCV-positive patients with antibody levels below or equal to 0.9 both have a low risk of surpassing the 1.5 threshold. [ABSTRACT FROM AUTHOR]

Background To assess the relationship between performance on the Paced Auditory Serial Addition Test ( PASAT) and both cerebral blood flow ( CBF) and axonal metabolic integrity in normal appearing white matter ( NAWM) of the centrum semiovale in patients with multiple sclerosis ( MS). Methods Normal appearing white matter of the centrum semiovale was investigated with magnetic resonance ( MR) imaging in 28 non-depressed individuals (18 patients with MS and 10 healthy controls). CBF was assessed with pseudo-continuous arterial spin labeling. N-acetylacetate/creatine ( NAA/ Cr) ratios (a metabolic axonal marker) were measured using 1H- MR spectroscopy. CBF was also measured in frontoparietal cortices and cerebellar hemispheres. Results In subjects with MS, we found a positive correlation between performance on the PASAT and CBF to the left centrum semiovale ( P = 0.008), but not with the NAA/Cr ratio. There were no correlations between PASAT scores and CBF to the right centrum semiovale, frontoparietal cortices, and cerebellar hemispheres. There was no correlation between PASAT scores and NAA/Cr ratios. Conclusions Our preliminary results suggest that performance on the PASAT in subjects with MS correlates with CBF to the left centrum semiovale, which contains left frontoparietal white matter association tracts involved in information processing speed and working memory. [ABSTRACT FROM AUTHOR]