Intravascular lymphoma is a rare but well-described entity. The clinical manifestations are heterogeneous. We report a case of a 59-year-old woman who presented initially with syncope followed by subacute cognitive decline that progressed to minimally conscious state. Shortly after the transfer to our tertiary center the patient died. Brain autopsy disclosed the diagnosis of B-cell intravascular lymphoma. We speculate that syncope could be the first manifestation of central nervous system intravascular lymphoma and should be considered in the differential diagnosis of unexplained syncope. In addition, we stress the importance of early brain biopsy in unexplained white matter disease.