Blood Glial Fibrillary Acidic Protein in MRI-Negative Attack-Like Episodes of Neuromyelitis Optica Spectrum Disorder.

objectivesMagnetic resonance imaging (MRI) is widely used to support relapse diagnosis in neuromyelitis optica spectrum disorder (NMOSD), yet some patients present with attack-like symptoms without corresponding lesions. We assessed serum glial fibrillary acidic protein (sGFAP) levels in MRI-negative attack-like episodes.

methodsWe retrospectively analyzed aquaporin-4-IgG-positive NMOSD patients presenting with relapse-like symptoms but without corresponding new MRI lesions. sGFAP was measured from stored serum collected at presentation and converted to demographic-adjusted z-scores. A predefined attack-associated threshold (z-score ≥ 3.0) was based on prior work.

resultsWe identified 39 MRI-negative attack-like episodes from 34 patients. Most episodes were clinically mild or subjective, with objective worsening observed in 23%. Eight episodes (21%) showed elevated sGFAP levels (median z-score 4.56 [1748 pg/mL]). Compared with episodes without elevated sGFAP, these episodes occurred closer to prior attacks (8 vs. 33 months) and more frequently met objective worsening criteria (50% vs. 16%). In all episodes with elevated sGFAP, remission samples showed normalization below the threshold. DISCUSSION: Marked sGFAP elevation in a subset of MRI-negative episodes suggests that some events may represent relapse not captured by conventional imaging. sGFAP may serve as a complementary biomarker to support attack identification when clinical and MRI findings are inconclusive.