“…The pro cess may begin acutely in a few hours or less, or develop subacutely over a period of several days [2], Early in this century, the illness was attributed to vascular disorders, including syphilis, atherosclerosis, and infection [3]. As additional cases were reported, other neuropathologic processes were identified and related to other possible etiologies, including parainfectious inflammatory disor ders [4][5][6][7][8], postvaccinal reactions [9][10][11][12][13][14][15], effects of chemicals and radiation [16][17][18], vascular malformations [19], demyelination as part of multiple sclerosis [20], and necrotic myelopathy as a remote effect of cancer [21,22], Early attempts to define acute transverse myelitis clinically come from sur veys of hospitalized patients [2,[23][24][25] in which the clinical criteria were usually as follows: acute nonrecurrent onset of bilateral, not always symme trical, cross-sectional sensorimotor deficit. Cases thought to be due to known systemic or focal neurologic disorders affecting the cord were usually excluded.…”