What are the diagnostic criteria for Neuromyelitis Optica (NMO) Spectrum Disorder?

From the Guidelines

Neuromyelitis optica spectrum disorder (NMOSD) diagnosis requires a combination of clinical evaluation, imaging studies, and laboratory testing, with a focus on the presence of core clinical characteristics and positive serum aquaporin-4 immunoglobulin G (AQP4-IgG) antibodies, as outlined in the revised diagnostic criteria proposed by the International Panel for NMO diagnosis 1.

Key Diagnostic Criteria

• The presence of at least one core clinical characteristic, such as optic neuritis, acute myelitis, area postrema syndrome, acute brainstem syndrome, symptomatic narcolepsy, or symptomatic cerebral syndrome, is required for NMOSD diagnosis.
• Positive AQP4-IgG testing is a key factor in diagnosis, with at least one core clinical characteristic required for NMOSD diagnosis in patients with a positive AQP4-IgG test.
• For AQP4-IgG negative patients or patients with unknown AQP4-IgG status, more stringent clinical criteria, with additional neuroimaging findings, are required, such as longitudinally extensive transverse myelitis lesions extending over three or more vertebral segments, or optic neuritis with brain MRI lesions 1.

Imaging Studies

• MRI findings play a crucial role in the diagnosis of NMOSD, with a focus on the optic nerve, spinal cord, area postrema, other brainstem, diencephalic, or cerebral presentations.
• Acute optic neuritis requires brain MRI showing normal findings or only nonspecific WM lesions, or optic nerve MRI with a T2-hyperintense or T1-weighted gadolinium-enhancing lesion extending over half the optic nerve length or involving the optic chiasm.
• Acute myelitis requires an associated intramedullary MRI lesion extending over 3 contiguous segments (longitudinally extensive transverse myelitis, or LETM) or 3 contiguous segments of focal spinal cord atrophy in patients with a history compatible with acute myelitis 1.

Laboratory Testing

• Testing for AQP4-IgG antibodies is essential in the diagnosis of NMOSD.
• Cerebrospinal fluid analysis may show pleocytosis with neutrophil predominance and elevated protein levels, but oligoclonal bands are typically absent, which helps differentiate NMOSD from multiple sclerosis.
• Testing for myelin oligodendrocyte glycoprotein (MOG) antibodies is also recommended as MOG-IgG positive disease represents a distinct entity with different treatment implications 1.

From the Research

Diagnosis of Neuromyelitis Optica Spectrum Disorder

• The diagnosis of Neuromyelitis Optica Spectrum Disorder (NMOSD) is based on clinical, neuroimaging, and laboratory features 2.
• Aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) are a diagnostic marker of the disease and play a significant role in its pathogenicity 3, 4.
• The presence of AQP4-IgG can help differentiate NMOSD from other conditions such as multiple sclerosis (MS) and myelin oligodendrocyte glycoprotein antibody-associated encephalomyelitis (MOG-EM) 5.
• Myelin oligodendrocyte glycoprotein (MOG)-IgG associated disorder (MOGAD) is a distinct nosologic entity that may be considered in the differential diagnosis of NMOSD, particularly in AQP4-IgG seronegative patients 4, 6.

Clinical Characteristics and Diagnostic Criteria

• NMOSD is characterized by inflammatory involvement of the optic nerve, spinal cord, and central nervous system 2.
• The clinical characteristics of AQP4-IgG seropositive and MOG-IgG seropositive patients may differ, with MOG-IgG seropositive patients more frequently presenting with coincident optic neuritis and transverse myelitis and having a monophasic disease course 6.
• The diagnosis of NMOSD requires a comprehensive evaluation of clinical, neuroimaging, and laboratory features, including the presence of AQP4-IgG or MOG-IgG antibodies 3, 5.

Laboratory Tests and Imaging Studies

• Laboratory tests, such as cell-based assays, can be used to detect the presence of AQP4-IgG and MOG-IgG antibodies 6.
• Neuroimaging studies, such as magnetic resonance imaging (MRI), can help identify lesions in the optic nerve, spinal cord, and brainstem, which are characteristic of NMOSD 2, 6.
• The use of MRI and other imaging modalities can help differentiate NMOSD from other conditions, such as MS and MOG-EM 5.