Acute transverse myelitis. A localized form of postinfectious encephalomyelitis.

We analysed the clinical, imaging, electrophysiological, laboratory findings, course and prognostic factors in 31 patients with acute transverse myelitis (20 men and 11 women; mean age, 30 years; range, 18-51 years). All patients were assessed for maximal clinical deficit 'deficit score'; pattern-shift visual, auditory and somatosensory evoked potentials were measured, CSF was examined, and neuroimaging of the spinal cord and brain (MRI or CT myelography) was carried out. The myelitis was preceded by febrile illness in 25 (81%) of the patients. The site of the lesion was cervical in 11 (36%), upper thoracic in two (6%), lower thoracic in 16 (52%). MRI of the spinal cord was abnormal in 10 out of the 20 patients examined (50%); in the remaining 11 patients, only CT was carried out and it was normal in all of them. Somatosensory evoked potentials were abnormal in 19 (61%), while pattern-shift visual and brainstem auditory evoked potentials were normal in all patients. CSF was abnormal in 94% of patients with pleocytosis, increased protein or both. Eighteen patients (58%) had good outcome. All patients had monophasic illness. Three variables have emerged as being associated with significant worsening of the outcome: (i) abnormal somatosensory evoked potentials; (ii) abnormal imaging and (iii) high 'deficit score' at onset. Acute transverse myelitis affects a complete segment of the spinal cord, is monophasic and represents a localized form of postinfectious acute encephalomyelitis.