RESUMEN
BACKGROUND: Acute Disseminated Encephalomyelitis (ADEM) is an acute demyelinating disorder of the central nervous system, characterize by multiple white matter hyperintensities on T2 MRI. Patients usually present with subacute progressive encephalopathy and polyfocal neurological deficits. Possible treatments are corticosteroids, immunoglobulins and plasma exchange. Full clinical recovery is seen in more than half of the cases. CASE: We describe a case of a 62-year-old patient presenting with thunderclap headache as the first symptom, two weeks after an upper respiratory tract infection. The clinical course was complicated by progressive coma and intracranial hypertension mandating external ventricular drainage and sedation. Initial treatment with methylprednisolone was unsuccessful but clinical resolution and radiological regression was achieved after plasma exchanges and cyclophosphamide. CONCLUSION: To our knowledge, this is the first reported case of ADEM presenting with thunderclap headache. Intracranial hypertension with the need for invasive neuromonitoring and pressure management is also a very rare complication of ADEM. In this report, we describe the findings of the literature review concerning ADEM, thunderclap headache and intracranial hypertension.