AQP4 water channels are thought to be the target of autoimmune attack in neuromyelitis optica-spectrum disorders (NMOsd). AQP4 are highly expressed on ventricular ependyma. The objective of this study was to describe a novel pattern of linear, 'pencil-thin' enhancement of ventricular ependyma in NMOsd. We report two NMOsd patients with pencil-thin ependymal enhancement along the frontal and occipital horns of lateral ventricles. Differential diagnosis of ependymal enhancement should include NMOsd alongside with infectious and neoplastic etiologies. Pencil-thin ependymal enhancement may be a helpful radiological marker of NMOsd that can be used to differentiate this condition from multiple sclerosis.