MRI features and evolution of autoimmune glial fibrillary acidic protein astrocytopathy: A retrospective cross-sectional and longitudinal study

Abstract

Background: Autoimmune glial fibrillary acidic protein astrocytopathy (AGA) is a relatively novel disease. The early diagnosis of this inflammatory central nervous system (CNS) disorder remains challenging.

Objectives: We aimed to explore the imaging manifestations and evolution of AGA to facilitate its successful diagnosis and monitoring.

Methods: From January 2016 to January 2021, a total of 15 consecutive patients, who were hospitalised in our institution and confirmed AGA clinically, were enrolled in this IRB-approved retrospective study. All clinical features and MRI manifestations were analysed cross-sectionally and longitudinally. Distribution, morphology, enhancement pattern and evolution of AGA lesions were assessed visually and evaluated semi-quantitatively by calculating the burden of disease (BOD) and the signal intensity ratio (SIR). Chi-square, Mann-Whitney U and Kolmogorov-Smirnov Z tests were performed for lesion patterns' statistical comparison.

Results: Fever, limb weakness, headache and cognitive impairment were the most common symptoms in AGA. 14 patients were initially misdiagnosed as infection (n = 9), demyelination (n = 4) or infarction (n = 1). The median time interval from onset to confirmed AGA diagnosis was 46 days. Both BOD and SIR progressed in the natural course and were relieved after immunotherapy on MRI. Meningeal enhancement, one of the most common MRI findings in patients with AGA (100%), relieved faster than intraparenchymal enhancement (p <0.001) and peri‑ventricular radial linear (PVRL) enhancement (p <0.001) after the initiation of immunotherapy. Non-enhanced lesions had lower BOD (p <0.001) and were relieved slower (p <0.001) than enhanced ones.

Conclusions: MRI provides valuable neuroradiological indicators for the diagnosis and follow-up of AGA. The CNS enhancement patterns (meningeal / PVRL) facilitate the early diagnosis and treatment response monitoring of AGA, while lesion manifestation in the spinal cord contributes to the follow-up. The evolution inconsistency of AGA lesions in different regions may be attributed to the discrepancy within glial fibrillary acidic protein subtypes.

Keywords: Autoimmune glial fibrillary acidic protein astrocytopathy; Differential diagnosis; Lesion evolution; Post-contrast MRI; Radiological indicators.