Marburg’s disease is a variant of multiple sclerosis which produces a monophasic fulminant course with extended edema and brain herniation refractory to intensive medical treatments and with poor outcome or dead. We report a case of a 31 years old female patient previously healthy who presented an hyperacute onset of pseudotumoral Marburg’s type of Multiple Sclerosis with left hemispheric massive brain swelling. On the seventh day of admission, patient’s intracranial pressure became uncontrolled in spite of medical aggressive treatment. Left decompressive hemicraniectomy allowed intracranial pressure control. Patient had an excellent outcome with an Expanded Disability Status Scale of 2.5.