In other study analysing 22 consecutive SS patients with CNS manifestations, 31.8% of them were positive for AQP4-Ab, and the abnormalities in the cerebrum and brainstem, as well as the optic nerve and the spinal cord, were more commonly found in AQP4-Ab-positive patients than in Ab-negative patients [64]. Here, AQP4 is linked to synovial sarcoma.