Introduction: Subdural empyema (SE) and subdural haematoma (SH) can present similar radiological signs on magnetic resonance imaging (MRI) of the brain. Natalizumab, a monoclonal antibody used in the treatment of multiple sclerosis (MS), exerts immunosuppressive effects in the CNS and can rarely be complicated by progressive multifocal leukoencephalopathy. In a 39-year-old female treated because of MS with natalizumab, control MRI showed massive thickening of the meninges and multiple fluid reservoirs, described as most probably empyemas and meningitis. The patient denied head trauma. Laboratory tests did not show inflammation. Orthopantomogram showed dental pathologies – a possible source of infection. Despite intense treatment, the MRI lesions remained unchanged. After neurosurgical intervention, chronic SH was diagnosed. A radiological picture of SH and SE could be difficult to differentiate. The aim of the article is to show how unspecific signs in neuroimaging can be caused by chronic SH.