The contribution of brain MRI
| Disease | Findings on brain MRI |
| Infarction | Normal, unless other process present |
| Haemorrhage | Normal +/−subarachnoid haemorrhage |
| MS | T2 white matter hyperintensities, Dawson fingers, periventricular lesions, juxtacortical lesions, T2 hyperintense lesions in the optic nerves may be present if optic neuritis has occurred. |
| NMOSD—aquaporin-4 antibody positive (43%–70%) | Periependymal lesions in deep grey matter structures, corpus callosum (‘arch bridge pattern’), area postrema. Large and/or confluent white matter lesions. When optic neuritis has occurred, long lesions in the optic nerve involving the posterior nerve and chiasm may differentiate NMOSD. |
| NMOSD—MOG antibody positive | May mimic aquaporin-4 antibody NMOSD features, with significant overlap of features. ‘Fluffy’ lesions may occur. |
| Systemic lupus erythematosus | Lacunar infarcts, cortical infarcts, white matter haemorrhages and large territorial infarcts have been noted in patients with systemic lupus erythematosus; more so if they have associated antiphospholipid syndrome. Note: patients with systemic lupus erythematosus may have associated aquaporin-4 antibody positive NMOSD. |
| Sjögren’s syndrome | MRI may show non-specific subcortical and periventricular T2 hyperintensities. Acute punctate infarcts. |
| Other autoimmune disorders | Non-specific findings/normal |
| ADEM | Multiple white matter T2 hyperintensities with incomplete ‘open-ring’ enhancement |
| Paraneoplastic | May mimic inflammatory or demyelinating lesions. NMOSD may also coexist with malignant conditions (causality not established) and so features on MRI may also be in keeping with this diagnosis. |
| Sarcoid | Leptomeningeal enhancement occurs in 40% of patients (especially basilar) and may lead to hydrocephalus in 5%–12% of patients. T2 hyperintense intraparenchymal lesions that typically enhance. Involvement of pituitary gland, hypothalamus and cavernous sinus may also occur. |
| Metabolic | Typical degeneration of white matter manifesting as extensive T2 hyperintense areas in the periventricular white matter (most common in vitamin B12 deficiency) |
| Malignancy | Normal/concurrent malignancy (both in primary and metastatic) |
ADEM, acute disseminated encephalomyelitis; MOG, myelin oligodendrocyte glycoprotein; MS, multiple sclerosis; NMOSD, neuromyelitis optica spectrum disorder.