DEVIC’S NEUROMYELITIS OPTICA (NMO) IS A SEPARATE ENTITY FROM MS AND SHOULD BE TREATED BY PLASMAPHERESIS (PRO)

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease, as is MS1. It has a monophasic form, which constitutes a minority of cases, and the relationship of this subtype to its vastly more common relapsing form remains uncertain2, 3. It is characterized primarily by optic neuritis and transverse myelitis, both of which are symptoms that can occur in MS. However, it is clinically, radiologically, and pathologically distinct from MS4. The relapsing form of NMO predominates in women (80-90 % of cases), and typically begins in late-middle age, although there is a childhood-onset form that may have some unique features5. Attacks are generally more severe than in MS, and accompanied by long lesions in spinal cord and optic nerve. Although the brain was previously thought to be spared, it is now well accepted that brain lesions occur, and often are distinct from those seen in MS6. Characteristic syndromes associated with brain involvement include intractable vomiting or hiccoughs7 associated with lesions in the dorsal medulla and encephalopathy associated with hypothalamic or brainstem/corpus callosum lesions, which are rarely seen in MS. Brain involvement is particularly prominent in children with NMO5. Pathologically, features that distinguish NMO from MS include prominent eosinophil/neutrophil infiltrate, prominent necrosis and cavitation in the cord, prominent perivascular deposition of immunoglobulin and activated complement components accompanied by hyalinization of blood vessels8. A serum autoantibody directed to aquaporin-4, when detected (in approximately 70 % of patients with this condition in contemporary series that use appropriately stringent clinical criteria), is able to distinguish NMO from MS and other conditions with which it might be confused9. When contemporary diagnostic criteria that incorporate clinical, radiological and serological studies are applied, M