Children with MOG-IgG positive bilateral optic neuritis misdiagnosed as fulminant idiopathic intracranial hypertension

Background: Fulminant idiopathic intracranial hypertension (IIH) is characterized by headache, rapid decrease of vision and elevated CSF-opening pressure. Objective: To delineate a subgroup of MOGAD mimicking fulminant IIH. Methods: In this case series children with MOGAD with vision loss, optic disc swelling and elevated CSF opening pressure, initially diagnosed with fulminant IIH, were included. Results: 8 MOGAD patients (median age 12.5y, f:m = 7:1) with an initial diagnosis of fulminant IIH were included. Rapid bilateral visual loss and headache was present in all patients in addition to bilateral optic disc swelling and decreased visual acuity. In 2 patients cMRI showed prominent optic discs or an empty sella sign. In 7 patients the CSF opening pressure was markedly elevated. Patients were treated with Acetazolamide (n = 6), CSF external drainage (n = 2) or implantation of VP shunt (n = 1). Intravenous Methylprednisolone was administered in all patients because of worsening of symptoms, positive MOG-ab titers and/or new MRI white matter lesions. Visual recovery was good with residuals in 1/8 children. OCT revealed thickening of pRNFL in the acute stage in all patients with a rapid declining of pRNFL and retinal atrophy thereafter. Conclusion: Children with bilateral MOGAD-ON presenting with loss of vision and elevated CSF opening pressure are at risk of being misdiagnosed as fulminant IIH. The role of elevated CSF opening pressure in MOGAD warrants further investigations. We recommend to include measurement of CSF opening pressure in the work up of neuroinflammatory diseases, in particular in patients with suspected MOGAD, to consider adapted pressure management.