A 22-year-old woman with systemic lupus erythematosus (SLE) presented to the emergency department with a flare-up of widespread macular rash, fever, malaise, nausea, vomiting, unsteadiness, headaches, sudden onset diplopia, and blurred vision. Conjugate horizontal nystagmus was noted. No abnormality was visible on the initial computed tomography scan of her brain. Magnetic resonance imaging (MRI) showed T2 hyperintensity in the dorsal pons and medulla (Figure 1A), with involvement of the facial colliculi and medial aspect of the superior and middle cerebellar peduncles (Figures 1B–1D, showing sections from the lower pons to the upper medulla). The appearance on MRI was consistent with neuroinflammation, and the distribution was correlated with her presenting symptoms and signs. There was concurrent proteinuria and her renal biopsy was consistent with lupus nephritis. Further signs of active SLE included an anti-dsDNA level greater than 400 IU/mL (reference range: 0 to 9 IU/mL), with low C3 and C4 and normal C-reactive protein levels. Anti-ribosomal P antibodies that are specific for SLE were present, and may have been associated with neurological involvement. The nystagmus can be explained by paramedian pontine reticular formation involvement. The area postrema is located in the caudal part of the floor of the fourth ventricle in the dorsal medulla. It serves as a chemoreceptor zone, acting primarily as the vomiting center. Area postrema syndrome is characterized by persistent nausea, vomiting, and hiccups. Lesions in this area can be associated with aquaporin-4 antibodies. These are typically found in neuromyelitis optica, but can also occur in individuals with SLE. Knowledge of this association is helpful to understanding neurolocalizing signs.
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