Clinical diagnosis
Case 195
【Progress】
She was given steroid pulse therapy and Tacrolimus. Her symptoms were improving but not completely cured. After admission to our hospital, she was being given rehabilitation training.
【Discussion】
Optic neuromyelitis is a disease which causes severe visual loss and transverse myelitis such as limb weakness, sensory loss and bladder & rectal dysfunction. The latter syndrome is, in the other word, called longitudinal extensive transverse myelitis (1-6). As other clinical characteristics, it is listed that area postrema syndrome: unexplained nausea and vomiting, symptomatic narcolepsy syndrome with typical diencephalic MRI lesions are related to optic neuromyelitis (7).
Optic neuromyelitis was previously thought to be the same clinical entity as multiple sclerosis. Aquaporin-4 antibody comes to positive when multiple sclerosis advances while it appears in early stage of optic myelitis, implying production of aquaporin-4 antibody is relevant to onset of optic neuromyelitis (2, 5). Our case had common cold and thereafter, this disease appeared. The pathogenesis of multiple sclerosis is yet to be clarified. Since the first prescribed medicine for optic neuromyelitis is different for multiple sclerosis: interferon and steroid for multiple sclerosis, while steroid or immunosuppressive for optic neuromyelitis (6-8), optic neuromyelitis should be distinct precisely from multiple sclerosis.
Aquaporin-4 is water channel on astrocyte cell membrane. Aquaporin-4 allows excessive water flow from astrocyte cell to vessels in order to keep from edema and to excrete harmful substances of potassium and excessive glutamate. When aquaporin-4 antibody produced by T cell passes through blood brain barrier, this disease onsets. Aquaporin-4 antibody associated with complements injures astrocyte cell membrane and recruits macrophages, neutrophils and eosinophils which destroy astrocytes (2, 5). Astrocyte gives nutrient to the oligodendrocytes and nerve cells. Further, astrocytes assist oligodendrocytes to form myelin which insulate nerve fibers. When astrocytes die, first myelin disappears and thereafter, oligodendrocytes and nerve cells die.
Radiologic characteristic between optic neuromyelitis and multiple sclerosis are a little different (6, 7, 9-12). Optic neuromyelitis appear lesions with high signal intensity on MRI with FLAIR at posterior part of optic chiasm, posterior limb & crus cerebrum (pyramidal tract), area postrema, diencephalic area (cortex surrounding third ventricle, midbrain aqueduct and fourth ventricle) and H-shaped gray matter in spinal cord. These areas except pyramidal tract are thought to be less functioning for blood brain barrier. Pyramidal tract is not the areas where aquaporin 4 is highly expressed (12); it is unknown why these areas are frequently involved. Meanwhile, multiple sclerosis appears as discrete, ovoid and perpendicular lesions at periventricular and callosal cortex with high signal intensity on MRI with FLAIR, and/or as open-ring gadolinium-enhanced lesions with well-defined borders at cerebral deep white matter.
In our case, she had several symptoms: easy to tiering to move eye balls, weakness of right extremities and rectal & urinary retention which are not contradictory with optic neuromyelitis. MRI with FLAIR showed high signal intensity corresponded to left pyramidal tract (posterior limb of internal capsule and crus cerebrum, corona radiata), corpus callosum and area postrema which are compatible with optic myelitis. However, MRI with FLAIR demonstrated bilateral oculomotor nerves with high signal intensity which are rare findings for optic myelitis.
【Summary】
We present a forty nine-year-old female suffering from progressive weakness of right upper extremity, and rectal and urinary retention. Bain MRI with FLAIR showed a lesion with high signal intensity at left posterior limb of internal capsule & left crus cerebrum, area postrema, corpus callosum and right deep white matter. It is borne in mind that aquaporin 4 plays a role of channel for astrocyte excreting excessive potassium and glutamate. Aquaporin 4 antibody associated with complement attack and destroy astrocytes which function to give nutrients to oligodendrocyte and nerve cells, resulting in demyelization and disappearance of these cells. Radiologic characteristic of optic neuromyelitis appear lesions with high signal intensity on MRI with FLAIR at posterior part of optic chiasm, posterior limb & crus cerebrum (pyramidal tract), area postrema, diencephalic area (cortex surrounding third ventricle, midbrain aqueduct and fourth ventricle) and H-shaped gray matter in spinal cord.
【References】
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2020.6.24