Describe the clinical features, diagnostic criteria, differential diagnosis and management of neuromyelitis optica spectrum disorders. [2+2+3+3]
Neuromyelitis optica spectrum disorders (NMOSD) are severe, relapsing inflammatory demyelinating disorders of the central nervous system, primarily affecting the optic nerves and spinal cord, often associated with aquaporin-4 antibody (AQP4-IgG) positivity (Harrison's 21e, Ch. 265).
NMOSD is an autoimmune astrocytopathy caused by IgG autoantibodies against aquaporin-4 water channels on astrocytes, leading to complement-mediated astrocytic injury, secondary demyelination, and neuronal damage. Some patients are AQP4-IgG negative but may have anti-myelin oligodendrocyte glycoprotein (MOG) antibodies with distinct clinical features.
| NMOSD Classification | Key Features |
|---|---|
| AQP4-IgG positive NMOSD | Classic disorder; severe longitudinally extensive transverse myelitis (LETM), optic neuritis (ON) |
| AQP4-IgG negative NMOSD | Seronegative; some positive for MOG-IgG; tends to have better prognosis |
| Clinical syndromes included in NMOSD | Optic neuritis, LETM (>3 vertebral segments), area postrema syndrome (hiccups, vomiting), brainstem and diencephalic syndromes |
(Harrison's 21e, Ch. 265; Bradley's Neurology, 8e)