Acute myelopathy of unknown aetiology: a clinical, neurophysiological and MRI study of short- and long-term prognostic factors.

Brain and spinal cord magnetic resonance imaging (MRI), multimodal evoked potentials (EPs) and cerebrospinal fluid (CSF) analysis were performed in 27 patients with acute myelopathy of unknown aetiology (AMUA), to detect the diagnostic and prognostic values of paraclinical tests at presentation. Spinal cord MRI was abnormal in 56% and brain MRI in 33% of the patients. Visual EPs were abnormal in 7%, median somatosensory EPs in 17%, tibial somatosensory EPs in 56% and motor EPs in 35% of the cases examined. Brain-stem acoustic EPs were normal in all the patients. CSF oligoclonal bands (OBs) were detected in 30% of cases. The patients were divided into subgroups according to the short-term clinical outcome (complete, partial or absent recovery). There were no significant differences among the three groups as regards MRI findings. Patients with complete recovery showed a significantly lower frequency of tibial somatosensory EP and motor EP abnormalities. According to the paraclinical findings at onset and on the basis of a long-term clinical follow-up (mean duration 24 months), 6 patients were diagnosed as having clinically definite multiple sclerosis, while 21 did not develop further neurological disturbances. Only the presence of CSF OBs was significantly more frequent in patients with definite multiple sclerosis. Our study indicates that EPs exploring spinal cord function are more powerful than spinal MRI for predicting the short-term outcome of AMUA, while the combined use of brain MRI and CSF OBs has the highest negative predictive value for the subsequent development of clinically definite multiple sclerosis.