Chapter 193: Neuromyelitis Optica
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Neuromyelitis optica (NMO; Devic’s disease) is an aggressive inflammatory disorder characterized by recurrent attacks of optic neuritis (ON) and myelitis; the more inclusive term NMO Spectrum Disorders (NMOSD) incorporates pts with partial forms, and with involvement of additional CNS structures ( Table 193-1 ). NMO is more frequent in women than men (>3:1), and typically begins in adulthood but can arise at any age. An important consideration is distinguishing between NMO and multiple sclerosis (MS; Chap. 192: Multiple Sclerosis ). In NMO, attacks of ON can be bilateral and produce severe visual loss (uncommon in MS); myelitis can be severe and transverse (rare in MS) and is typically longitudinally extensive ( Fig. 193-1 ) involving three or more contiguous vertebral segments. Also in contrast to MS, progressive symptoms typically do not occur in NMO.
|Diagnostic Criteria for NMOSD with AQP4-IgG|
|Diagnostic Criteria for NMOSD without AQP4-IgG or NMOSD with Unknown AQP4-IgG Status|
|Core Clinical Characteristics|
|Additional MRI Requirements for NMOSD without AQP4-IgG and NMOSD with Unknown AQP4-IgG Status|
Brain MRI may be normal or show areas of nonspecific signal change as well as lesions associated with specific syndromes such as the hypothalamus causing an endocrinopathy; the lower medulla presenting as intractable hiccoughs or vomiting; or cerebral hemispheres producing focal symptoms, encephalopathy, or seizures. Large MRI lesions in the cerebral hemispheres may have a “cloud-like” appearance and, unlike MS lesions, are often not destructive and can resolve completely. Spinal cord MRI lesions typically consist of focal enhancing areas of swelling and tissue destruction, extending over three or more spinal cord segments, and on axial sequences, these are centered on the gray matter of the cord. CSF findings include pleocytosis greater than in MS, with neutrophils and eosinophils in many acute cases; oligoclonal bands are uncommon.
NMO is an autoimmune disease associated with a highly specific autoantibody directed against the water channel protein aquaporin-4 (AQP4) that is present in the sera of approximately 70% of pts with a clinical diagnosis of NMO. AQP4 is localized to the foot processes of astrocytes. Pathology reveals inflammation, loss of astrocytes, and an absence of staining of AQP4 by immunohistochemistry, plus thickened blood vessel walls, demyelination, and deposition of antibody and complement.