Patients with neuromyelitis optica spectrum disorder (NMOSD) have increased magnetic resonance imaging (MRI) T2-relaxation times (T2rt) compared to healthy controls, according to a new study published in the Journal of Neurology, Neurosurgery & Psychiatry. Those patients with active NMOSD had even further increased T2rt compared to those who were clinically stable.
Increased T2rt was observed in both white and gray matter structures of patients with NMOSD during the study, with P values ranging from .014 to <.0001 when compared to those of healthy controls. Patients with NMOSD with active disease had similar clinical and MRI features but increased T2rt in normal-appearing white matter (NAWM; P =.002) and gray matter (P =.010) compared to patients with stable disease.
“Despite similar demographic features with [healthy controls], patients with NMOSD had a widespread increase of T2rt in the NAWM, [gray matter] and basal ganglia, except for the pallidum,” the authors said.
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“The T2rt might be sensitive to the inflammatory activity in NMOSD, but the timing of its changes are yet to be determined,” the authors said, “Future longitudinal studies are needed to confirm these results and to explore correlations with markers of astrocyte damage (ie, GFAP) in order to prove a dependency between the pathogenic mechanism of NMOSD and this MRI measure.”
Univariate logistic regressions revealed associations between disease activity and T2rt in the NAWM (P =.003) and gray matter (P =.005), while a trend was observed in the thalamus (P =.05). Stepwise binary logistic regression found that only the T2rt of the NAWM was independently associated with disease activity status (P <.001).
The authors hypothesized that since NMOSD generally involves autoantibodies that target aquaporin-4 (AQP4) water channels on astrocytes, the resulting damage may result in blood-brain barrier permeability. This increased permeability would lead to changes in brain water content.
“Although the best strategy to measure water content is by estimating the quantitative proton density or exploiting the correlation with the longitudinal T2rt, the quantification of T2rt can also serve the aim in case of unchanged macromolecular concentration (ie, myelin content), with the advantage of being derivable from a clinically feasible dual-echo sequence,” the authors explained.
In the study, 77 patients with AQP4-seropositive NMOSD were enrolled along with 105 healthy controls from 2 clinical sites in Europe between April 2007 and January 2017. Patients had a median expanded disability status scale of 4.0 and a median disease duration of 4.3 years.
Cacciaguerra L, Pagani E, Radaelli M, et al. MR T2-relaxation time as an indirect measure of brain water content and disease activity in NMOSD. J Neurol Neurosurg Psychiatry. Published online April 28, 2022. doi:10.1136/jnnp-2022-328956