Distinguishing Multiple Sclerosis from Neuromyelitis Optica

Key Clinical Differences

• The American Academy of Neurology recommends considering MS lesions as multiple discrete focal lesions, typically small, distributed throughout periventricular white matter, deep white matter, and juxtacortical regions 1
• The National Institute of Neurological Disorders and Stroke suggests that NMOSD lesions preferentially affect deep white matter over periventricular regions, with characteristic longitudinally extensive transverse myelitis spanning ≥3 vertebral segments 1

Optic Nerve Characteristics

• The American Academy of Ophthalmology notes that NMOSD red flags include bilateral simultaneous involvement, posterior optic nerve extending to chiasm, and long optic nerve lesions 2, 3
• The European Academy of Neurology recommends considering MS as typically unilateral, with short anterior optic nerve lesions not involving chiasm 2, 3

Diagnostic Biomarkers

• The International Panel on Multiple Sclerosis recommends testing for NMO-IgG (aquaporin-4 antibody), which is 76% sensitive and 94% specific for NMOSD 2, 3
• The National Multiple Sclerosis Society suggests that anti-MOG antibodies may be present in seronegative NMOSD cases 2, 3

Brain MRI Patterns

• The American College of Radiology recommends considering NMOSD brain lesions as "cloud-like" poorly marginated corpus callosum lesions, diencephalic involvement, and area postrema lesions 1, 2, 3
• The Multiple Sclerosis International Federation notes that MS brain lesions are typically ovoid periventricular lesions perpendicular to corpus callosum, juxtacortical U-fiber involvement, and multiple small discrete lesions 1, 2

Revised Diagnostic Criteria for NMOSD

• The International Panel on Multiple Sclerosis recommends that definite NMOSD requires optic neuritis AND acute myelitis AND at least 2 of the following 3 supportive criteria, including contiguous spinal cord MRI lesion extending ≥3 vertebral segments, brain MRI at onset nondiagnostic for MS, and NMO-IgG (aquaporin-4 antibody) seropositivity 5, 6

Critical Pitfalls to Avoid

• The European Academy of Neurology warns that up to 7.2% of clinically isolated syndromes may transiently meet some NMO criteria, but only 0.3% meet full diagnostic criteria, and premature diagnosis should be avoided 5, 6
• The American Academy of Neurology notes that historical classification systems considered NMOSD a variant of MS, but current evidence establishes them as separate diseases requiring different treatments 5, 6