Quantitative 7T MRI does not detect occult brain damage in neuromyelitis optica

Area of Science:

• Neuroimaging
• Neurology
• Radiology

Background:

• Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) are distinct inflammatory demyelinating diseases of the central nervous system.
• Aquaporin-4 (AQP4) antibodies are specific to NMOSD, targeting AQP4-rich periependymal regions.
• Subtle, occult white matter damage may precede overt lesions in these conditions.

Purpose of the Study:

• To compare occult damages in AQP4-rich periependymal regions between NMOSD patients, MS patients, and healthy controls (HCs).
• To investigate the utility of quantitative T1 mapping at 7 Tesla (T) for detecting subtle neuropathology.

Main Methods:

• A cross-sectional study involving 11 NMOSD patients, 7 MS patients, and 10 HCs.
• High-resolution 7T MRI including T2*-weighted imaging and MP2RAGE sequences for T1 mapping.
• Semiautomated segmentation of lesion-free periependymal areas around ventricles and cerebral aqueduct for T1 relaxation time measurement.

Main Results:

• No significant differences in T1 relaxation time were observed in periependymal regions between NMOSD patients and HCs.
• Patients with MS exhibited longer T1 relaxation times in periependymal regions compared to both NMOSD patients and HCs.
• These differences were statistically significant in several periventricular areas and the cerebral aqueduct.

Conclusions:

• Subtle T1 changes were not detected in the periependymal regions of NMOSD patients, contrasting with findings in MS patients.
• This suggests that brain pathology in NMOSD is predominantly focal rather than diffuse.
• Quantitative T1 mapping at 7T can differentiate between MS and NMOSD based on periependymal region involvement.