neuromyelitis optica also known as devic s disease is a rare immune mediated demyelinating condition of the central nervous system affecting predominantly the optic nerves and the spinal cord . nmo can be seen as a part of another immune - mediated syndrome , such as lupus , multiple sclerosis , but often no underlying cause can be found . it should be included as one of the central nervous system ( cns ) neuroinflammatory disorders , , .   in the past , we have learned that nmo is far broader , and includes cases with unilateral optic neuritis , partial transverse myelitis and many cases in which optic neuritis and transverse myelitis are separated by months and years , . currently , nmo is considered as a central nervous system aqp4 channelopathy which causes variable damage predominantly to the optic nerves and spinal cord , although other cns structures that highly express aqp4 may be also affected , . we report the case of a 20-year - old caucasian woman who presented to the ophthalmology emergency room , claiming progressive , painless vision loss in the left eye with 3 days of evolution and one week after she complained paresthesias in the lower extremities . the patient presented a visual acuity of 10/10 in right eye and in the left eye absent luminous perception . the intraocular pressure was 13 mmhg in both the eyes and fundoscopy in the left eye showed edema of optic nerve and venous engorgement and tortuosity bilaterally ( figure 1 ( fig . the patient performed in the emergency room a ct and blood tests . on the same day she was admitted to the neurology department where she performed mri ( figure 2 ( fig . 3 ) ) , lumbar punction with analysis of csf . more specific tests and chest ct for screening of thymoma were requested . on the next day our patient was seen at the ophthalmology department where she made the following imaging tests : optical coherence tomography , angiography , visual fields and electrophysiological tests . the complementary exams realized in emergency room ( brain and orbits ct and blood tests ) were normal , except the slight increase of the inflammatory parameters . on the next day , angiography , retinography and oct visual fields were performed and the left eye showed a discrete arcuate scotoma and lower decrease in sensitivity thresholds in the superior temporal quadrant , right eye was normal . the csf was analysed to identify the presence of serum proteins , evidence of blood - brain barrier breakdown and the presence of oligoclonal banding that were negative ; quantitative analysis of the total protein , the total white cell count , differential white cell and cytology . the onset of the syndrome varies , from adolescent to young adulthood , with a median peak incidence in the late 30s , , . nmo is often associated with other autoimmune disorders in the patient or in the family . nmo manifests the sole clinical syndrome , with serological markers of autoimmunity , like a positive ana , rheumatic factor or thyroglobulin antibody . association with infectious disorders , like tuberculosis , viral infections and immunizations have been observed . this distinction is based on clinical , imaging , pathological and serological criteria and has practical implications , in the prognosis and therapies . since 2004 with the discovery of the nmo - specific antibody and aqp4 , as its targeted antigen , it is recognized as a turning point in the concept and understanding of the disease . aquaporin-4 is the most abundant water channel in the central nervous system , expressed in the foot processes of astrocytes in contact with blood vessels throughout the brain , spinal cord and optic nerves . the periventricular area , the hypothalamus and the brainstem are also considered sites of high expression of aqp-4 . although aqp-4 predominates in the cns , it is also found in other organs such as kidneys , stomach , airways , glands and skeletal muscle . however , the paucity of clinical abnormalities outside the cns remains to be explained , as well as the underlying mechanisms of aqp4-igg seronegative status in some patients , , . presumed reasons include , suboptimal sensitivity of the currently available assays ( specific for 91% of cases , but not very sensitive yet , 73% , of this could be explained because the substrates of the immunofluorescence assay were not human , but are from mousse brain tissues ) , very low serum concentration of the antibodies or their absence at some periods in the disease course , and the inhibitory effect of previous treatment with corticosteroids or immunosuppressive agents . it is also possible that in some nmo patients other antigens may play a role in the pathogenesis of the disease . therefore , notwithstanding a positive serum aqp4-igg test is of utmost importance for the diagnosis of nmosd , a negative result alone can not rule out the diagnosis , . for this reason acute or relapsing involvement of the optic nerves and spinal cord , coincidental or separated by months or yearsa . acute or relapsing involvement of the optic nerves and spinal cord , coincidental or separated by months or years a. serology . acute or relapsing involvement of the optic nerves and spinal cord , coincidental or separated by months or yearsb . optic neuritis can be unilateral or bilateral.absence in general , of central nervous system symptoms and signs outside the spinal cord and optic nerves , with exception of hypothalamic and lower brainstem dysfunctioncourse . the disease can either be monophasic or recurrent.spinal cord mri . can be normal , but often t2 signal abnormalities with cavitation and sometimes swelling , extending over 3 or more consecutive segments might reinforce the criteriabrain mri . in general , normal brain mri . white matter anomalies might sometimes be seen in hypothalamus and lower brainstem and rarely in the brain parenchyma . acute or relapsing involvement of the optic nerves and spinal cord , coincidental or separated by months or years b. serology . absence in general , of central nervous system symptoms and signs outside the spinal cord and optic nerves , with exception of hypothalamic and lower brainstem dysfunction course . . can be normal , but often t2 signal abnormalities with cavitation and sometimes swelling , extending over 3 or more consecutive segments might reinforce the criteria brain mri . in general , normal brain mri . white matter anomalies might sometimes be seen in hypothalamus and lower brainstem and rarely in the brain parenchyma . positive serum nmo - igg this new classification with revised diagnostic criteria represent an important advance in nmo research and clinical practice . they discriminate nmo from ms and allow the diagnosis of partial forms and negative nmo - igg forms , like our patient . in general , nmo is more acute , sometimes fulminant . myelitis , like optic neuritis , can also be fulminant , with acute urinary retention , paraparesis or quadriparesis , severe tonic flexor spasms and severe back pain . brain mri generally shows no white matter abnormalities in the brain , brainstem and cerebellum . spinal cord rmi can be supportive when continuous lesions with gadolinium enhancement extend over 3 or more vertebral segments . the prognosis of nmo is , in general , more guarded than that of ms patients . patients with nmo can die from acute ventilator failure produced by necrosis of the cervical cord and its complications . predictors of mortality in relapsing nmo include a history of systemic autoimmune disease , greater exacerbation frequency during the first 2 years of disease and better motor recovery after the first myelitis attack , . the treatment of the acute attack need hospitalization , particularly when rapid developing paraplegia or quadriplegia occurs . for those attacks the customary treatment is giving iv methylprednisolone , 1,000 mg q / day for 5 days continue with steroids in the form of oral prednisone , with very slow tapering over months in the relapsing forms of the disease . plasmapheresis has been found to help in patients with severe attacks that worsen during corticosteroid therapy or do not demonstrate improvement . predictors of response included early treatment initiation , male sex and preserved deep tendon reflexes.during the relapsing disease , patients with nmo can receive prednisone ( 1 mg / kg / d ) and azathioprine ( 23 mg / kg / d ) , , . according to some studies most patients receive a maintenance doses of azathioprine of 75150 mg together with 10 mg of prednisone dose q / o / d . our patient during hospitalization received methylprednisolone , 1,000 mg q / day ( iv ) for 5 days , following with steroids in the form of oral prednisone ( 1 mg / kg / d ) . at hospital discharge ( three weeks later ) , our patient showed partial recovery of left eye acuity and improvement of muscle strength of upper and lower limbs . five weeks later , the patient repeated the mri , that showed swelling diminished and sign change became less intense and smaller ( figure 4a and b ( fig . 4 ) ) , however the left frontal lesion maintains ( figure 4c ( fig . 4 ) ) and the vascular tortuosity and the no edema in the fundus had improved ( figure 4f ( fig . four months later , the dilated fundus examination showed a sectorial optical atrophy in the left eye ( figure 5b ( fig . 5 ) ) with a visual acuity 20/20 in each eye . at the moment she was receiving prednisone 40 mg / d and azathioprine 150 mg / d . nmo has a distinct clinical , imaging , pathological and immunopathological features sufficient to distinguish it from ms . this distinction is not just academic , because the treatment and the prognosis is different too , nmo optic neuritis can be fulminant and devastating . because a small proportion of cases nevertheless fulfill the criteria for both nmo and ms , challenges persist for clear definitions , especially concerning the roles of immunomodulatory and immunosuppressive treatment . early recognition of the relapsing form may allow expeditious acute and long - standing treatment and prevent significant morbidity and mortality .
introduction : neuromyelitis optica ( nmo ) is a severe demyelinating syndrome characterized by optic neuritis ( on ) and acute myelitis . the nmo spectrum is actually recognized to typically evolve as a relapsing disorder that also includes patients with atypical unilateral on and those with index events of on and myelitis occurring weeks or even years apart ( jarius / wildemann 2013 ) . 
 nmo was previously assumed to be a variant of multiple sclerosis ( ms ) , but the discovery of aquaporin-4 antibodies in patients with neuromyelitis optica has led to this view being revised ( mandler 2006 , barnett / sutton 2012 , wingerchuk et al . 
 2007 ) . 
 the cause of the condition is still unknown , but it has been shown that the antibodies bind selectively to a water channel expressed mainly on astrocytes at the blood - brain - barrier , which has an important role in the regulation of brain volume and ion homeostasis . 
 however , there are some patients with nmo that are antibodies negative . 
 the diagnosis is made on the basis of case history , clinical examination , magnetic resonance imaging ( mri ) of the brain and spinal cord , analysis of cerebrospinal fluid ( csf ) , visual evoked potentials and a blood test with analysis of aquaporin-4 antibodies ( barnett / sutton 2012 , wingerchuk et al . 2007 , thornton et al . 
 2011 ) . 
 this suggests that periodical revisions of established concepts and diagnostic criteria are necessary.purpose : the authors describe an extremely rare case of neuromyelitis optica and the aim of this paper is to call attention for the cases of nmo whith nmo - igg negative.methods : the selected method is a case report.results : to date the patient showed partial recovery of left eye acuity and improvement of muscle strength of upper and lower limbs and does not show recurrence of the disease.conclusion : nmo has a distinct clinical , imaging and immunopathological features sufficient to distinguish it from ms . 
 this distinction is essential , because the treatment and the prognosis is different .