MR T2-relaxation time as an indirect measure of brain water content and disease activity in NMOSD.

Objective: Since astrocytes at the blood-brain barrier are targeted by neuromyelitis optica spectrum disorder (NMOSD), this study aims to assess whether patients with NMOSD have a subclinical accumulation of brain water and if it differs according to disease activity.
Methods: Seventy-seven aquaporin-4-positive patients with NMOSD and 105 healthy controls were enrolled at two European centres. Brain dual-echo turbo spin-echo MR images were evaluated and maps of T2 relaxation time (T2rt) in the normal-appearing white matter (NAWM), grey matter and basal ganglia were obtained. Patients with a clinical relapse within 1 month before or after MRI acquisition were defined 'active'. Differences between patients and controls were assessed using z-scores of T2rt obtained with age-adjusted and sex-adjusted linear models from each site. A stepwise binary logistic regression was run on clinical and MRI variables to identify independent predictors of disease activity.
Results: Patients had increased T2rt in both white and grey matter structures (p range: 0.014 to <0.0001). Twenty patients with NMOSD were defined active. Despite similar clinical and MRI features, active patients had a significantly increased T2rt in the NAWM and grey matter compared with those clinically stable (p range: 0.010-0.002). The stepwise binary logistic regression selected the NAWM as independently associated with disease activity (beta=2.06, SE=0.58, Nagelkerke R ² =0.46, p<0.001).
Conclusions: In line with the research hypothesis, patients with NMOSD have increased brain T2rt. The magnitude of this alteration might be useful for identifying those patients with active disease.
Competing Interests: Competing interests: LC received speaker and consultant honoraria from ACCMED, Roche, BMS Celgene, and Sanofi. EP received speaker honoraria from Biogen Idec. MR reports no disclosures. SM has received grants or contracts from the Ministry of Education and Science, Republic of Serbia (Project 175031); and payment or honoraria for lectures, presentations, manuscript writing, or educational events from Merck Serono and Novartis; and support for attending meetings from Bayer, Genzyme Sanofi, Medis, Merck, and Schering. VM received honoraria for consulting services or speaking activity from Biogen, Merck, Novartis, TEVA, Almirall, and Sanofi. JI has nothing to report. JD has received travel support and/or research grants and/or lecture fees and/or advisory services from Novartis, Bayer, Merck, Sanofi Genzyme, Roche, Teva, Medis, Hemofarm, and Medtronic. MF is Editor-in-Chief of the Journal of Neurology, Associate Editor of Human Brain Mapping, Associate Editor of Radiology, and Associate Editor of Neurological Sciences; received compensation for consulting services and/or speaking activities from Almiral, Alexion, Bayer, Biogen, Celgene, Eli Lilly, Genzyme, Merck-Serono, Novartis, Roche, Sanofi, Takeda, and Teva Pharmaceutical Industries; and receives research support from Biogen Idec, Merck-Serono, Novartis, Roche, Teva Pharmaceutical Industries, Italian Ministry of Health, Fondazione Italiana Sclerosi Multipla, and ARiSLA (Fondazione Italiana di Ricerca per la SLA). MAR received speaker honoraria from Bayer, Biogen, Bristol Myers Squibb, Celgene, Genzyme, Merck Serono, Novartis, Roche and Teva, and receives research support from the MS Society of Canada and Fondazione Italiana Sclerosi Multipla.
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