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Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disease of the central nervous system that most commonly affects the optic nerves and spinal cord. Accurate differentiation from multiple sclerosis and MOGAD is particularly important because long-term treatment strategies for these disorders differ substantially.
Dr. Lidiia Prakhova is a neurologist and Doctor of Medical Sciences specializing in neuroimmunology and demyelinating disorders of the central nervous system. A consultation may include reassessment of the diagnosis, review of AQP4-IgG and MOG-IgG results, evaluation of brain and spinal cord MRI studies, and selection or reassessment of long-term relapse-prevention therapy.
Neuromyelitis optica spectrum disorder (NMOSD) is a group of autoimmune inflammatory disorders of the central nervous system. The optic nerves, spinal cord, brainstem, and area postrema are among the most characteristic sites of involvement.
Historically, neuromyelitis optica, also known as Devic disease, was considered a form of multiple sclerosis. NMOSD is now recognized as a distinct disease with different immunological mechanisms, MRI characteristics, prognosis, and treatment principles.
Antibodies against aquaporin-4 are detected in a substantial proportion of patients. AQP4-IgG is a major biomarker of NMOSD and a key component of modern diagnostic assessment.
Disability in NMOSD is largely related to residual damage from individual inflammatory attacks. Rapid treatment of an attack and prevention of further attacks are therefore central goals.
Treatment strategies used for multiple sclerosis should not automatically be transferred to NMOSD. Some MS therapies are ineffective in NMOSD and may potentially worsen disease activity.
Persistent unexplained hiccups, nausea, or vomiting, especially without a convincing gastrointestinal cause, may be a characteristic manifestation of NMOSD.
Double vision, facial sensory symptoms, dizziness, and other manifestations of brainstem involvement may occur. Diencephalic and cerebral syndromes are less common.
NMOSD should not be diagnosed on the basis of a single MRI scan or a single symptom. Diagnosis requires integration of the clinical presentation, antibody testing, and characteristic neuroimaging findings.
Whenever possible, bring the actual brain and spinal cord MRI studies in addition to the written reports, AQP4-IgG and MOG-IgG results, cerebrospinal fluid findings, discharge summaries from previous attacks, and a list of current and previously used medications.
Optic neuritis, myelitis, and MRI lesions may occur in all three disorders. However, the underlying immunology, typical MRI patterns, prognosis, and especially long-term treatment strategies differ.
| NMOSD | MOGAD | Multiple sclerosis | |
|---|---|---|---|
| Main biomarker | AQP4-IgG in a substantial proportion of patients | MOG-IgG | No disease-specific serum antibody |
| Optic neuritis | Often severe; may be bilateral and may involve the posterior optic nerve or optic chiasm | Frequently severe and sometimes bilateral; anterior optic nerve involvement and optic disc swelling are relatively characteristic | More commonly unilateral, with relatively good visual recovery |
| Myelitis | Frequently longitudinally extensive, involving three or more vertebral segments | May be long or short; conus involvement can occur | Spinal cord lesions are typically shorter and more peripheral |
| Other typical manifestations | Area postrema, brainstem, and diencephalic syndromes | ADEM and cortical syndromes, particularly in children and younger patients | Typical periventricular, juxtacortical, and infratentorial lesions |
| Long-term strategy | Rapid treatment of attacks and effective prevention of further attacks | Acute attack treatment; the need for maintenance therapy depends on disease course and relapse risk | MS-specific disease-modifying therapies are used |
This table summarizes typical patterns. Individual patients may have atypical findings, and diagnosis is always based on the complete clinical and laboratory picture.
Time matters in NMOSD. A severe attack can leave significant permanent neurological disability, so treatment is generally started without unnecessary delay.
Initial treatment of an acute attack usually includes high-dose intravenous methylprednisolone. The exact regimen depends on the clinical situation.
Plasma exchange should be considered early in severe attacks or when the response to corticosteroids is inadequate. In severe optic neuritis or myelitis, prolonged delay while waiting for a steroid response may not be appropriate.
In AQP4-IgG-positive NMOSD, recurrent attacks are a major determinant of long-term disability. Once the diagnosis is established, relapse-prevention immunotherapy is generally considered.
Several therapeutic mechanisms are now available. Treatment selection depends on AQP4-IgG status, previous attacks, comorbidities, infection risk, age, pregnancy planning, previous therapies, and treatment availability.
Therapies targeting the B-cell compartment include rituximab and targeted anti-CD19 treatment with inebilizumab.
Eculizumab and ravulizumab inhibit the terminal complement pathway, which plays an important role in tissue injury in AQP4-IgG-positive NMOSD.
Meningococcal infection prevention, appropriate vaccination, and infection-safety measures are particularly important when complement inhibitors are used.
Satralizumab targets interleukin-6 receptor signaling and can be used to prevent attacks in appropriate patients with NMOSD.
Conventional immunosuppressive therapies may still be appropriate in selected clinical situations. Their role depends on the availability of targeted therapies, tolerability, comorbidities, and the individual risk profile.
Regulatory approval, indications, availability and insurance coverage of individual therapies may change. Access to a particular treatment in Israel should therefore be assessed individually.
In rare neuroimmunological disorders, specialist consultation is particularly useful when the goal is not simply to assign a diagnostic label, but to make a practical decision about further investigation and treatment.
Integration of medical history, neurological findings, AQP4-IgG and MOG-IgG results, cerebrospinal fluid findings, and MRI to determine whether the presentation meets criteria for NMOSD.
Assessment of the location and characteristics of lesions in the brain, spinal cord, and optic pathways in the context of NMOSD, MOGAD and multiple sclerosis.
Assessment of the need for long-term treatment, possible therapeutic mechanisms, contraindications, and individual risk factors.
Review of the recent attack, current treatment, and whether the long-term therapeutic strategy should be changed.
A consultation may be useful for patients with established NMOSD, suspected neuromyelitis optica, recurrent optic neuritis, transverse myelitis, or a difficult differential diagnosis between NMOSD, MOGAD and multiple sclerosis.