Rapidly evolving severe Multiple Sclerosis with ADEM-like first clinical attack

M.A.C.F., 27 years old, physiotherapist, healthy. In December/2021, he presented subacute evolving imbalance and reduced visual acuity. Later on, he developed altered state of consciousness, drowsiness and seizures. CSF showed no signs of infection. Brain MRI revealed T2- hyperintensive multiple asymmetrical and tumefactive lesions throughout the parenchima and brainstem, with T1 Gadolinium enhancement(T1Gd+). Initial diagnosis: ADEM. Received pulse therapy with methylprednisolone for five days with little improvement. He was transferred to a referral hospital where he performed: 1- new CSF analisys, normal; 2- IV Methylprednisolone 3g; 3- six sessions of plasmapheresis, with significant neurological improvement. Control brain MRI (March/22): significant reduction in the number and volume of lesions. April/22: New gait instability. Brain MRI showed: new T2 and T1Gd+ lesions. He received IV Methylprednisolone 5g with partial improvement. Brain MRI in September/22 showed asymptomatic new T2 lesions T1Gd+. CSF analisys on Sep 6th/2022: Type 3 oligoclonal bands. Anti-MOG negative on 10/11/2022. In November/22:he once again presented clinical activity: drowsiness, gait impairment and bradypsychism. New brain MRI: new and active lesions. IV Methylprednisolone 5g led to partial neurological improvement. December/2022: peripheral facial paralysis, with no other associated deficits. He underwent new pulse therapy and plasmapheresis. February/2023: ataxia, nystagmus, urinary and fecal incontinence: once again received IV Methylprednisolone 5g. Hypothesis of rapidly evolving severe multiple sclerosis was raised and Natalizumab was initiated on February 2nd/23.Discussion: Multiple sclerosis and ADEM are two demyelinating diseases of the central nervous system, which share some similarities, but with different prognosis and treatment. In some cases the initial clinical presentation of such diseases may be indistinguishable, but cases of multiple sclerosis that have ADEM as the first presentation are rare. Final comments: The differentiation between ADEM and MS in this case is paramount due to their high inflammatory activity and the need for rapid specific treatment.