Acute transverse myelopathy (ATM) is a large group from various etiologies including multiple sclerosis, systemic diseases, post-infectious myelopathy, spinal cord infarct and neuromyelitis optica. In about 20% of cases, the etiology remains unknown even after a long-term follow-up. We call these cases "idiopathic ATM". The poor prognosis of ATM makes necessary an early diagnosis to avoid therapeutic delay. The aim of this review is to describe clinical and laboratory data concerning ATM allowing to improve diagnostic and therapeutic approaches. (C) 2009 Societe nationale francaise de medecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.