Differential brainstem atrophy in multiple sclerosis and neuromyelitis optica spectrum disorders among Hong Kong Chinese

Abstract

Introduction: Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are the most common inflammatory demyelinating disorders of central nervous system in Hong Kong. Brainstem is commonly involved in both disorders. We aimed to study the regional brainstem atrophy of local MS and NMOSD patients. Methods: Semi-automated segmentation and volumetric measurement of brainstem were performed and compared among MS, NMOSD, and healthy controls (HC). Clinical symptoms and severity were graded using Expanded Disability Status Scale (EDSS) and Kurtzke Functional System Scores (FSS). Associations between the volumes of interest (VOIs) and clinical disability scores were assessed by partial correlation and multiple regression analyses. Results: Baseline characteristics were comparable across the three groups, without significant difference in disease duration and severity between MS and NMOSD subjects. Normalised whole brainstem, midbrain, and pons volumes were significantly smaller in MS subjects compared to HC (-5.2%, P=0.027; -8.3%, P=0.000; and -5.9%, P=0.048; respectively) while only the normalised medulla volume was significantly smaller in NMOSD subjects compared to HC (-8.5% vs HC, P=0.024). Normalised midbrain volume was significantly smaller in MS compared to NMOSD subjects (-5.0%, P=0.014) while normalised medulla volume was significantly smaller in NMOSD compared to MS subjects (-8.1%, P=0.032). Smaller normalised whole brainstem, pons, and medulla oblongata volumes were associated with greater disability on EDSS, FSS-brainstem, and FSS-cerebellar in NMOSD patients. Conclusion: Our findings revealed different patterns of brainstem atrophy between MS and NMOSD patients. This can be related to different underlying pathologies and pathophysiological mechanisms.