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English: Typical patterns of NS observed on brain MRI including leptomeningeal and pachymeningeal disease, perivascular infiltration, MS-like lesions, which may represent coexistent disease, mass-like lesions, cranial nerve infiltration, and pituitary/meningeal disease. (A.a–A.b) Post-gadolinium T1 MRI from a patient with probable NS demonstrating leptomeningeal enhancement predominantly affecting the base of the brain (arrows). (B.a) T2/FLAIR MRI of definite NS demonstrates T2 hyperintensity in the occipital lobe (arrow) adjacent to an area of (B.b) dural thickening and enhancement (arrow) on post-gadolinium T1 MRI. (C) Post-gadolinium T1 MRI demonstrating multifocal perivascular meningeal enhancement in the subcortical white matter (arrows) and cortex (arrowhead) in definite NS. (D) Sagittal FLAIR MRI of the same patient from B, exhibited T2 hyperintense lesions in the cerebellum (not shown) as well as the periventricular and juxtacortical white matter (arrows). Atrophy associated with the occipital lobe T2 hyperintense lesion can be appreciated (arrowhead). This patient was diagnosed with multiple sclerosis and later developed pachymeningeal thickening biopsy proven to be sarcoidosis. (E.a) Post-gadolinium T1 MRI demonstrating a focal area of contrast enhancement in the left insula (arrow) with (E.b) parenchymal T2 hyperintensity on FLAIR in a patient with probable neurosarcoidosis. (F.a) Mass-like lesion in the right mesial temporal lobe with enhancement (arrow) on post-gadolinium T1 MRI with corresponding (F.b) swelling and T2 hyperintensity on FLAIR (arrow) in definite NS. Note that most mass-like lesions in NS have some meningeal component as seen in E and F. (G) Coronal post-gadolinium T1 MRI demonstrating left optic nerve enhancement (arrow) in a patient with probable NS who presented with left optic neuritis. (H) Axial post-gadolinium T1 MRI with contrast enhancement and swelling in Meckel cave about the left trigeminal nerve (arrow) in a patient with probable NS who developed left trigeminal neuropathy (pain and decreased sensation). (I) Axial post-gadolinium T1 MRI demonstrating contrast enhancement in both internal auditory meatuses (arrows) in a patient with probable NS and bilateral facial nerve palsy. (J) Sagittal post-gadolinium T1 MRI in a patient with definite NS who presented with hypopituitarism demonstrates abnormal contrast enhancement and swelling of the pituitary gland (arrowhead) and stalk (arrow).