What clinical features should prompt me to suspect Neuromyelitis Optica Spectrum Disorder (NMOSD) in a patient?

Clinical features that should prompt suspicion of Neuromyelitis Optica Spectrum Disorder (NMOSD) include:

• Severe, often bilateral optic neuritis presenting with visual loss, eye pain, and impaired colour vision.
• Longitudinally extensive transverse myelitis (LETM), characterised by acute myelitis symptoms such as limb weakness, sensory disturbances, and bladder or bowel dysfunction, typically involving three or more contiguous spinal cord segments on MRI.
• Area postrema syndrome, presenting as intractable nausea, vomiting, or hiccups due to involvement of the dorsal medulla.
• Acute brainstem syndromes causing symptoms such as diplopia, facial weakness, or respiratory failure.
• Symptomatic narcolepsy or diencephalic syndrome with hypothalamic involvement.
• Other cerebral syndromes including encephalopathy or seizures, although less common.

These features are distinct from multiple sclerosis and should raise clinical suspicion for NMOSD, especially when supported by MRI findings and serological testing for aquaporin-4 antibodies NICE NG220. Recent literature emphasises the importance of recognising overlapping features with related disorders such as Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD), which can present with similar optic neuritis and myelitis but differs in antibody profile and prognosis Sechi et al. 2022.