MULTIPLE SCLEROSIS MSJ

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1 431727MSJ / Estiasari et al.multiple Sclerosis Journal 2012 Research Paper MULTIPLE SCLEROSIS JOURNAL MSJ Comparison of clinical, immunological and neuroimaging features between anti-aquaporin-4 antibody-positive and antibody-negative Sjögren s syndrome patients with central nervous system manifestations Multiple Sclerosis Journal 18(6) The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalspermissions.nav DOI: / msj.sagepub.com Riwanti Estiasari 1,*, Takuya Matsushita 2,*, Katsuhisa Masaki 1, Takuya Akiyama 1, Tomomi Yonekawa 1, Noriko Isobe 1 and Jun-ichi Kira 1 Abstract Background and objective: The objective of this study is to clarify clinical, immunological, and neuroimaging features in anti-aquaporin-4 (AQP4) antibody-positive and antibody-negative Sjögren s syndrome (SS) patients with central nervous system (CNS) involvement. Methods: Medical records and MRI scans were retrospectively analyzed in 22 consecutive SS patients with CNS manifestations. Results: Seven (31.8%) patients were positive for anti-aqp4 antibodies. The frequency of visual impairment was higher in anti-aqp4 antibody-positive patients than in antibody-negative patients (71.4% vs. 0.0%, p = ). Brain MRI showed that discrete lesions were more commonly found in the cerebrum, brainstem, and optic nerve in anti-aqp4 antibodypositive patients than in antibody-negative patients (p = 0.002, p = 0.006, and p = 0.004, respectively), while spinal cord MRI showed that posterior column lesions in the cervical spinal cord were more frequent in anti-aqp4 antibodypositive patients than in antibody-negative patients (71.4% vs. 14.3%, p = 0.01). SS-A antibody titers were higher in anti- AQP4 antibody-positive patients than in antibody-negative patients (p = 0.012) and were also higher in patients with longitudinally extensive spinal cord lesions (LESCLs) than in those without LESCLs (p = 0.019). Conclusions: In SS, the presence of anti-aqp4 antibodies is associated with involvement of the optic nerve, cerebrum and brainstem, and with cervical posterior column lesions in the spinal cord. Keywords antibody, aquaporin-4, central nervous system, multiple sclerosis, neuromyelitis optica, Sjögren s syndrome Introduction Neuromyelitis optica (NMO) is an inflammatory disease that selectively affects the optic nerves and spinal cord. In NMO, longitudinally extensive spinal cord lesions (LESCLs) extending three or more vertebral segments are characteristic. 1 The nosological position of NMO has long been debated. The discovery of an IgG specific for NMO, 2 initially designated NMO-IgG but now known to be an anti-aquaporin-4 (AQP4) antibody, 3 suggests that NMO is a distinct disease entity with a fundamentally different etiology from multiple sclerosis (MS). 4 In the relapsing form of NMO, systemic autoimmune diseases and other systemic autoantibodies frequently coexist; 5 most frequently, Sjögren s syndrome (SS) and minor salivary gland inflammation. 6 1 Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. 2 Department of Clinical Neuroimmunology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. * These authors contributed equally to this work. Corresponding author: Jun-ichi Kira, Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Maidashi, Higashi-ku, Fukuoka , Japan. kira@neuro.med.kyushu-u.ac.jp

2 808 Multiple Sclerosis Journal 18(6) Only two Korean reports provide detailed descriptions of central nervous system (CNS) involvement in NMOassociated SS patients. 7,8 In one report, a very high frequency of NMO and SS myelitis coexistence was found in a selected series of patients. 7 Myelitis was found in 8 of 112 SS patients; all 8 had LESCLs, and of 5 SS myelitis patients examined for anti-aqp4 antibody, all were positive. It was concluded that SS myelitis is a manifestation of NMO caused solely by anti- AQP4 antibody. The other report examined 12 SS patients with recurrent CNS manifestation who were recruited by a nationwide survey in Korea. These 12 patients showed atypical brain lesions, such as lesions adjacent to the third and fourth ventricles, large cerebral or cerebellar lesions, and cavity-like formation. 8 However, before the discovery of NMO-IgG, SS was reported to have a variety of effects on the CNS, including myelopathy, encephalopathy and MS-like manifestations Therefore, it remains to be elucidated whether SS myelitis is exclusively induced by anti-aqp4 antibodies and whether all brain lesions show atypical NMOlike features. We thus aimed to clarify clinical, immunological, and neuroimaging characteristics between anti-aqp4 antibody-positive and antibody-negative SS patients with CNS involvement in an unselected population. Materials and methods Subjects This retrospective study included 22 consecutive patients (20 females and 2 males) with CNS manifestations associated with SS who were admitted to the neurology ward of Kyushu University Hospital during Patients were subjected to magnetic resonance imaging (MRI) of the brain and/ or spinal cord and were assayed for the presence of anti-aqp4 antibodies. The diagnosis of SS was established by the 1999 Japan Revised Criteria (Supplementary Table 1). 12 All patients underwent thorough neurological examinations and routine laboratory tests. All were followed up and clinically evaluated in the outpatient clinic. Their medical records and MRI films were retrospectively analyzed in the present study by anti- AQP4 antibody status-blinded examiners (RE, KM, and TA). The disability status of the patients was scored according to the Expanded Disability Status Scale (EDSS) of Kurtzke 13 at relapse and 1 4 weeks after a treatment. SS patients were classified into those with NMO 4 /NMO spectrum disorder (NMOSD) 14 and those without NMO/NMOSD. Responses to treatment were evaluated based on alterations of EDSS scores at the time of relapse before and after each treatment modality. Responders were defined as those whose EDSS scores improved by at least one after 1 4 weeks of treatment following a relapse. Anti-AQP4 antibody assay Anti-AQP4 antibody was measured with an immunofluorescence method using GFP-AQP4 (M1 isoform) fusion protein-transfected HEK-293 cells, as described previously. 15 The experimenters were blind to the origin of the specimens and the anti-aqp4 antibody assay was carried out at least twice for each sample. Samples that gave a positive result twice were deemed to be positive. Magnetic resonance imaging All MRI studies were performed using a Magnetom Vision and Symphony 1.5 T (Siemens Medical Systems, Erlangen, Germany), as described previously. 16 Brain MRI was performed on 22 patients and spinal cord MRI on 21 patients. MRI scans were taken at the time of clinical relapse or at onset in 21 patients (within 30 days) and in 1 patient at a remission phase (56 days after onset). Statistical analysis The frequency of any given observation between anti- AQP4 antibody-positive and antibody-negative patients was compared by Fisher s test. Normally distributed values (age at onset and examination, duration of neurological illness, SS-A antibody titer, and peak EDSS score) were compared by Student s t-test. Non-normally distributed values [IgG index, CSF cell count (/µl) and protein level (mg/dl), relapse rate, and SS-B antibody titer] were compared by the Mann Whitney U-test. In all assays, statistical significance was set at p < Results Demographic and clinical features CNS manifestations of each patient in this study are shown in Supplementary Table 2. Patient age at the onset of neurological symptoms and duration of neurological illness were ± (mean ± SD) years and 5.59 ± 4.73 years, respectively. Two patients developed neurological manifestations affecting the CNS 8 and 9 years after SS diagnosis. Both ocular and oral symptoms were observed in seven (31.8%) patients. Salivation and serological examinations and minor salivary gland histopathology gave positive results in 13/20 (65.0%), 21/22 (95.5%), and 11/16 (68.8%) of patients, respectively. Seven (31.8%) patients were positive for anti-aqp4 antibody, while the other patients were negative. Seven patients also presented other autoimmune diseases; rheumatoid arthritis (n = 2), idiopathic thrombocytopenic purpura (n = 2), systemic lupus erythematosus (n = 1), mixed connective tissue disease (n = 1), and Basedow s disease (n = 1). Among these, five patients were anti-aqp4 antibody positive. Table 1 shows the comparison of clinical features between anti-aqp4 antibody-positive and antibody-negative patients. Acute onset was more common in anti-aqp4 antibody-positive patients than in antibody-negative patients (100.0% vs. 26.7%, p = ) while chronic

3 Estiasari et al. 809 Table 1. Demographic features of patients with Sjögren s syndrome and CNS involvement. AQP4 antibodypositive (n = 7) AQP4 antibodynegative (n = 15) p value Age at onset of neurological symptoms, y ± ± Duration of neurological illness, y 8.01 ± ± Annualized relapse rate 0.83 ± ± Peak EDSS score 5.64 ± ± Final EDSS score 3.21 ± ± Onset Chronic* 0 (0.0) 8 (53.3) Subacute 0 (0.0) 3 (20.0) Acute* 7 (100.0) 4 (26.7) Neurological manifestation Higher brain dysfunction 3 (4.9) 1 (6.7) Visual impairment* 5 (71.4) 0 (0.0) Numbness 6 (85.7) 12 (80.0) 1.0 Decreased position sense 1 (14.3) 9 (60.0) Decreased vibration sense 4 (57.1) 11 (73.3) 0.63 Motor weakness 4 (57.1) 8 (53.3) 1.0 Hyperreflexia 6 (85.7) 10 (66.7) 0.14 Pathological reflex 3 (42.9) 8 (53.3) 1.0 Dyskinesia 4 (57.1) 12 (80.0) 0.33 Brainstem sign 3 (42.9) 2 (13.3) 0.27 Cerebellar sign 1 (14.3) 2 (13.3) 1.0 Autonomic impairment 5 (71.4) 5 (33.3) 0.17 CSF Cell count (/µl) (n = 21) ± ± Protein level (mg/dl) (n = 22) ± ± IgG index (n = 20) 0.63 ± ± OB (n = 20) 2/6 (33.3) 7/14 (50) 0.64 Meet 2005 McDonald criteria 15 * 6 (85.7) 1 (6.7) Meet 2006 NMO Criteria 4 * 4 (57.1) 1 (6.7) SS symptoms Ocular symptoms 3 (42.9) 4 (26.7) 0.63 Oral symptoms 4 (57.1) 3 (20.0) 0.14 Decreased salivation a 4 (57.1) 9/13 (69.2) 0.65 SS-A/B antibodies 7 (100.0) 14 (93.3) 1.0 Salivary gland pathology 3/4 (75.0) 8/12 (66.7) 1.0 SS-A antibody titer (U/ml)** ± ± SS-B antibody titer (U/ml) 51.7 ± ± Other autoimmune diseases 5 (71.4) 2 (13.3) Percentages in parentheses. AQP4 = aquaporin-4; SS = Sjögren s syndrome; EDSS = Expanded Disability Status Scale of Kurtzke, 13 ; OB = oligoclonal IgG bands. *Fisher s test p < **Student s t-test p < a Salivation was tested by either the gum test or the Saxon test. onset was more frequently seen in anti-aqp4 antibodynegative patients than in antibody-positive patients (53.3% vs. 0.0%, p = 0.022). No significant differences in clinical findings were noted, except for a higher frequency of visual impairment in the anti-aqp4 antibody-positive patients compared with the antibody-negative patients (71.4% vs. 0.0%, p = ). All five patients who had visual impairment were positive for anti-aqp4 antibody and four of these five patients also showed hyperintense lesions in the optic nerve on T2-weighted MRI images (Figure 1). The percentage of brainstem signs was more than three-fold higher in anti-aqp4 antibody-positive patients compared with antibody-negative patients, although it did not reach statistical significance. Final EDSS scores were not different between the two groups, even though the peak EDSS scores were slightly higher in the anti-aqp4 antibody-positive group. CSF analysis revealed greater cell counts and protein levels in anti-aqp4 antibody-positive patients

4 810 Multiple Sclerosis Journal 18(6) Table 2. Brain and spinal cord MRI findings. MRI abnormality AQP4 antibodypositive (n = 7) AQP4 antibodynegative (n = 15) Brain MRI findings Any brain lesions 6/7 (85.7) 5/15 (33.3) Cerebrum* 6/7 (85.7) 2/15 (13.3) Brainstem* 6/7 (85.7) 3/15 (20.0) Midbrain 2/6 (33.3) 0/3 (0.0) 0.50 Pontine tegmentum 1/6 (16.7) 1/3 (33.3) 1.00 Ventral pons 0 (0.0) 1/3 (33.3) 0.33 Medulla 3/6 (50.0) 1/3 (33.3) 1.00 Cerebellum 0 (0.0%) 2/15 (13.3%) 1.00 Optic nerve* 4/7 (57.1) 0 (0.0) Barkhof brain lesion 2/7 (28.6) 0/15 (0.0) Gd enhanced lesion 1/7 (14.3%) 0/15 (0.0%) T2 brain lesion 2/7 (28.6) 1/15 (6.7) juxtacortical lesion 2/7 (28.6) 1/15 (6.7) periventricular lesion 2/7 (28.6) 0/15 (0.0) Paty brain lesion 2/7 (28.6) 0/15 (0.0) Ovoid lesion 2/7 (28.6) 0/15 (0.0) Bilateral diencephalic lesions 1/7 (14.3) 0/15 (0.0) 0.32 Cavity formation 2/7 (28.6) 0/15 (0.0) Spinal cord MRI findings Any spinal cord lesions 6/7 (85.7) 6/14 (42.9) 0.16 LESCL 4/7 (57.1) 2/14 (14.3) 0.12 Gd-enhanced lesions 4/7 (57.1) 2/14 (14.3) 0.12 Cervical cord lesions 5/7 (71.4) 6/14 (42.9) 0.36 Anterior column 2/7 (28.6) 0/14 (0.0) 0.10 Lateral column 1/7 (14.3) 3/14 (21.4) 1.00 Posterior column* 5/7 (71.4) 2/14 (14.3) Central gray matter 3/7 (42.8) 3/14 (21.4) 0.35 Thoracic cord lesions 5/7 (71.4) 5/14 (35.7) 0.18 Anterior column 2/7 (28.6) 0/14 (0.0) 0.10 Lateral column 2/7 (28.6) 2/14 (14.3) 0.57 Posterior column 2/7 (28.6) 2/14 (14.3) 0.57 Central gray matter 2/7 (28.6) 2/14 (14.3) 0.57 Lumbosacral cord lesions 0/0 (0.0) 2/14 (14.3) 0.53 Cauda equina lesions 0/0 (0.0) 1/14 (7.1) 1.00 Percentage in parentheses. AQP4 = aquaporin-4; Gd = gadolinium; LESCL= longitudinally extensive spinal cord lesion; OB = oligoclonal IgG bands. *Fisher s test p < p value compared with antibody-negative patients, but this difference was not statistically significant. Fulfillment of the revised NMO criteria 4 and the McDonald criteria 15 for MS was more common in anti-aqp4 antibody-positive patients than in antibody-negative patients (57.1% vs. 6.7%, p = 0.02, and 85.7% vs. 6.7%, p = , respectively). SS-A antibody titers were significantly higher in anti-aqp4 antibody-positive patients compared with antibody-negative patients (p = 0.012). Magnetic resonance imaging findings Brain MRI showed that discrete lesions were more common in the cerebrum, brainstem, and optic nerve in anti-aqp4 antibody-positive patients than in antibody-negative patients (p = 0.002, p = 0.006, and p = 0.004, respectively) (Table 2). Brain lesions fulfilling Barkhof s criteria 17,18 were found only in anti-aqp4 antibody-positive patients. Ovoid lesions and atypical brain lesions, such as bilateral diencephalic lesions and cavity formation, were also found only in anti- AQP4 antibody-positive patients. Spinal cord MRI showed that the frequencies of cervical, thoracic and lumbar spinal cord lesions, and LESCLs were not significantly different with respect to anti-aqp4 antibody status, while the posterior column lesions within the cervical spinal cord were observed significantly more frequently in patients with anti-aqp4 antibodies than in those without (71.4% vs. 14.3%, p = 0.01) (Figure 2A D, G, H).

5 Estiasari et al. 811 Figure 1. Optic nerve MRI of a representative Sjögren s syndrome case with extensive optic nerve lesions and positive for AQP4 antibody. A 36 year-old female with Sjögren s syndrome had episodes of recurrent optic neuritis on both sides and paresthesia in both lower limbs due to thoracic myelitis over the preceding 4 years. Her EDSS score was 4.0 before an exacerbation of a large visual field defect in the left eye, but no other symptoms. She had no LESCLs according to spinal cord MRI. Her AQP4 antibody titer was 1:16,384. She had a recurrence of left optic neuritis and became blind. Corticosteroid pulse therapy initiated 9 days after the onset of relapse only partially improved her visual loss. The axial T2-weighted image shows slight hyperintensity in the left optic nerve (A). Coronal sections of T2-weighted images show hyperintensity in intraorbital (B), intraoptic canal (C), and intracranial (E) portions of the left optic nerve. The optic nerve was contrast-enhanced in T1-weighted images (D). Sagittal FLAIR image showing hyperintensity of the left optic nerve along its entire length from the retrobulbar portion to the chiasma (F). Each bar in the left-hand side panel indicates the position of the coronal section on the right panel. An arrow in each photo indicates the optic nerve lesion. SS-A antibody titers were significantly higher in patients with cerebral lesions or LESCLs compared with patients without (cerebral lesion-positive ± 76.1 vs. cerebral lesion-negative ± 48.29, p = 0.039, and LESCLpositive ± vs. LESCL-negative ± 53.93, p = 0.019), while other MRI findings, such as brainstem, optic nerve, cerebellar, cervical cord, and thoracic cord lesions, were not related to SS-A antibody titers, and SS-B antibody titers had no correlation with any MRI findings. Comparison of clinical and neuroimaging features between SS patients with and without NMO/NMOSD When SS patients with and without NMO/NMOSD were compared, frequencies of acute onset and visual impairment was significantly more frequent in the former than in the latter (p = and p = , respectively). Anti-AQP4 antibody was positive in seven of nine (77.8%) SS patients with NMO/NMOSD. Furthermore, frequencies of optic neuritis, any spinal cord lesions, and LESCL on MRI were significantly higher in SS patients with NMO/ NMOSD than in those without NMO/NMOSD (p = , p = , and p = , respectively) (Table 3). Treatment response All patients, except for two patients who were lost to follow up, initially received corticosteroid treatment. Three patients then had plasma exchange and intravenous high dose immunoglobulin (IVIg) administration, two had IVIg alone and five had plasma exchange alone. Three patients were administered azathioprine and one received tacrolimus for maintenance therapy. Responders to corticosteroid pulse therapy were more commonly positive for anti-aqp4 antibody than non-responders (p = ) (Table 4 and

6 812 Multiple Sclerosis Journal 18(6) Figure 2. Representative spinal cord T2-weighted MRI scans of Sjögren s syndrome patients. (A, B) A 28 year-old male with decreased visual acuity, eye pain, dysphagia and paresthesia in both lower extremities. Disease duration was 6.57 years and peak EDSS was 8.5. He was positive for AQP4 antibody but had no CSF oligoclonal bands. SS-A and SS-B antibody titers were 152 and 18 U/ml, respectively. He was also diagnosed with systemic lupus erythematosus. Cervical cord MRI revealed LESCLs at the fifth cervical to fourth thoracic spine levels. The lesion resided mainly in the posterior column extending to the central gray matter with additional lesions in the left lateral column, as seen on axial T2-weighted images at level C6. (C F) A 21 year-old female with a diagnosis of Sjögren s syndrome 8 years before neurological symptoms. Duration of neurological illness was 5.04 years and peak EDSS was 9.5. The patient was positive for both AQP4 antibody and CSF oligoclonal bands. SS-A and SS-B antibody titers were 209 and 211 U/ml, respectively. She received methylprednisolone pulse therapy as an initial treatment which ameliorated her illness. She continued on low-dose oral prednisolone and tacrolimus for maintenance therapy. Sagittal T2-weighted images at relapse (C) show LESCLs and spinal cord edema, while an axial image at level C5 (D) indicates the lesion is located mainly in the posterior column extending to the central gray matter. Cervical cord MRI after treatment during remission phase (E, F) shows the resolution of the LESCL and spinal cord edema. (G, H) A 56 year-old female SS patient negative for anti-aqp4 antibody. Duration of neurological illness was 2.0 years and peak EDSS was 6.0. SS-A and SS-B antibody titers were 137 and 0 U/ml, respectively. Sagittal T2-weighted images reveal LESCLs at levels C2 to C6, while an axial image at level C4 shows the lesion located mainly in the central gray matter. Figure 2E H). Brainstem lesions were more frequently detected in responders, compared with non-responders (p = 0.022). Eight patients underwent plasma exchange and improvement was observed in four, two of whom were positive for anti-aqp4 antibody. Five patients received IVIg and it was effective in three, one of whom was positive for anti-aqp4 antibody. Discussion In contrast to the previous studies on SS patients associated with NMO, our study determined the following: (1) Anti-AQP4 antibody is present in one-third of SS patients with CNS manifestations. (2) Anti-AQP4 antibody is associated with the emergence of visual impairment. (3) Anti- AQP4 antibody is associated with higher SS-A antibody titers and a higher frequency of other coexistent autoimmune diseases. (4) Anti-AQP4 antibody is associated with MRI lesions in the cerebrum, brainstem, optic nerve, and posterior column of the cervical spinal cord. (5) SS-A antibody titers are higher in patients with LESCLs and with cerebral lesions. (6) Anti-AQP4 antibody-positive SS patients responded to corticosteroids better than antibodynegative patients. Although the present study is the first to

7 Estiasari et al. 813 Table 3. Comparison of clinical and neuroimaging features between Sjögren s syndrome patients with and without NMO/NMOSDs Sjögren s syndrome with NMO/NMOSDs(n = 9) Sjögren s syndrome without NMO/NMOSDs (n = 13) p value Females/males ratio 8/1 12/ Age at onset, y 34.6 ± ± Peak EDSS score 5.4 ± ± Final EDSS score 3.2 ± ± Onset Chronic 1 (11.1) 7 (53.8) Subacute 0 (0.0) 3 (23.1) 0.24 Acute 8 (88.9) 3 (23.1) Visual impairment* 5 (55.6) SS symptoms Ocular symptoms 3 (33.3) 4 (30.8) 1.00 Oral symptoms 4 (44.4) 3 (23.1) 0.38 Decreased salivation a 4/7 (57.1) 9 (69.2) 0.65 Anti-AQP4 antibody positivity* 7 (77.8) CSF Cell count (/µl) 14.0 ± 28.1 (n = 8) 6.4 ± Protein level (mg/dl) ± ± IgG index 0.60 ± 0.15 (n = 8) 0.70 ± 0.32 (n = 12) 0.54 OB 2/8 (25.0) 7/12 (58.3) 0.20 ANA 2 (15.4) 11 (84.6) 1.00 SS-A 9 (100) 10 (76.9) 0.55 SS-B 5 (55.6) 5 (38.5) 0.57 RF 3 (33.3) 1 (7.7) 0.71 MRI Any brain lesions 7 (77.8) 4 (30.8) Optic neuritis* 4 (44.4) Any spinal cord lesions* 8 (88.9) 4/12 (33.3) LESCL* 6 (66.7) 0/ Percentage in parentheses. AQP4 = aquaporin-4; EDSS = Expanded Disability Status Scale of Kurtzke, 13 ; LESCL = longitudinally extensive spinal cord lesion; OB = oligoclonal IgG bands. *Fisher s test p < a Salivation was tested by either the gum test or the Saxon test. study an unselected series of SS patients with CNS involvement with respect to anti-aqp4 antibody status, the retrospective nature of the study performed in a tertiary hospital and a relatively small number of subjects limited the statistical power of the study. In the present study, we used the M1 isoform of AQP4 for the anti-aqp4 antibody assay. Tanaka et al. 19 used an immunofluorescence method with the M23 isoform and found a positivity rate among selected Japanese NMO patients that was only slightly higher than that in our study; therefore, we believe that our usage of the M1 isoform did not significantly distort the results. It is still possible that anti-aqp4 antibody-negative SS patients with LESCLs might be positive for the antibody if the M23 isoform was used as an antigen. This needs to be clarified by future studies using the M23 isoform. Higher titers of SS-A antibody and a greater frequency of other autoimmune diseases in anti-aqp4 antibody-positive patients indicate an importance of an autoimmune background for anti-aqp4 antibody production. We previously reported that among anti-aqp4 antibody carriers, the antibody titer showed a significant negative correlation with the percentage of peripheral blood Th1 cells and that patients with SS-A/B antibody had significantly higher anti-aqp4 antibody titers compared with those without SS-A/B antibody. 15 Collectively, heightened humoral autoimmunity seems to contribute to the production of high titer anti-aqp4 antibody. Anti-AQP4 antibody is associated with visual impairment and the occurrence of optic nerve lesions, which is consistent with previous reports showing severe optic nerve involvement in NMO patients with NMO-IgG/AQP4 antibody. 20 The frequency of optic nerve lesions on MRI is also significantly higher in anti-aqp4 antibody-positive patients than in anti-aqp4 antibody-negative patients. 21 It was reported that anti-aqp4 antibody-positive patients showed a lack of visual evoked potential responses, whereas anti-aqp4

8 814 Multiple Sclerosis Journal 18(6) Table 4. Comparison of laboratory findings between responders and non-responders to corticosteroid pulse therapy. Corticosteroid pulse therapy p value Responders (n = 9) Non-responders (n = 11) AQP4 antibody-positive* 5 (55.6) 1 (9.1) 0.05 SS-A antibody titer (U/ml) ± ± SS-B antibody titer (U/ml) 43.2 ± ± MRI lesions Cerebrum 6 (66.7) 2 (18.2) Brainstem* 7 (77.8) 2 (18.2) Optic nerve 3 (33.3) 1 (9.1) 0.29 LESCL 2 (22.2) 3 (27.3) 1.00 Percentage in parentheses. Abbreviations: AQP4 = aquaporin-4; LESCL = longitudinally extensive spinal cord lesion. *Fisher s test p < antibody-negative patients demonstrated delayed latency. 22 These observations reflected a necrotic process underlying the lesions in anti-aqp4 antibody-positive patients. Moreover, anti-aqp4 antibody is associated with a high frequency of cerebral and brainstem lesions, which is also in accord with a previous study that indicated a higher frequency of cerebral and brainstem lesions in NMO patients with anti-aqp4 antibody compared with those without and showed frequent occurrence of lesions adjacent to the fourth ventricles. 15,16 On the other hand, we also observed occasional coexistence of MS-like brain lesions in our anti- AQP4 antibody-positive SS patients with CNS involvement. These latter findings are also compatible with previous reports demonstrating that MS-like brain lesions are also detected in NMO-IgG/anti-AQP4 antibody carriers. 22 We 23 and others 24 have reported the presence of AQP4 in the perivascular astrocyte foot processes in human cerebral white matter; therefore, it is feasible that anti-aqp4 antibody could also target the cerebral white matter, which may partly explain the high frequency of cerebral involvement in the present SS patients with anti-aqp4 antibody. Several studies reported MS-like CNS manifestations in SS patients. 11,25 27 Massara et al. 11 noted that among 25 patients with SS and CNS involvement, 5 patients had MS-like CNS involvement. On the other hand, increased prevalence of primary SS was also reported in MS; although there was no agreement on the incidence of primary SS in MS, the highest rates were reported to be as high as 16.6% in primary progressive MS by De Seze et al. 25 and 50% in Asian relapsing remitting MS by Wang et al. 26 These observations indicate that SS patients can develop a variety of brain lesions, some of which appear MS-like. In our study, a third of patients with LESCLs were seronegative for anti-aqp4 antibody. Pittock et al. 5 reported that in six patients with coexistent SS/SLE and NMO, three did not have NMO-IgG. There might be other factors that play roles in the development of LESCLs and NMO in SS patients beside the AQP4 antibody. In the present study, the finding that SS-A antibody titers were higher in SS patients with LESCLs compared to those without suggests that SS-A antibody is related to the occurrence of LESCLs in SS patients. In addition, the most frequently observed lesions are located in the posterior column of the cervical spinal cord. This is distinct from the preferential site of involvement in NMO with anti-aqp4 antibody, which is the central gray matter of the thoracic cord. 16 Therefore, both an association between SS-A antibody titers and LESCLs and the distinct involvement of the spinal cord in anti-aqp4 antibody-positive SS patients suggest the possibility that factors other than anti-aqp4 antibody are involved in lesion formation in SS myelitis with LESCLs, even in those patients positive for anti-aqp4 antibody. This might explain why LESCLs were not significantly associated with anti-aqp4 antibody in the present SS patients. One of the lesion-initiating factors could be SS-A antibody because SS-A antigen is present in endothelial cells 28 and SS-A antibody is supposed to cause endothelial cell damage. 28 In animal models of NMO, factors which break down the blood brain barrier, such as myelin basic protein-specific T cells, and bacterial lipopolysaccharide, 32 are needed for NMO-IgG to act in the CNS. Otherwise, NMO-IgG needs to be injected directly into the CNS parenchyma. 33 Thus, it is possible that SS-A antibody may initiate BBB breakdown and then anti-aqp4 antibody may enter across the weakened BBB and destroy astrocyte endfeet. Such a possibility needs to be tested in an experimental model. Finally, although the sample size was small due to a single institutional series, treatment response to corticosteroids seemed to be better in anti-aqp4 antibody-positive SS patients compared with antibody-negative SS patients. The CNS involvement usually responds poorly to immunotherapies in SS patients; 34 however, the present findings suggest

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