Diffusion Tensor Imaging in Idiopathic Acute Transverse Myelitis

OBJECTIVE: Our study was based on our hypotheses that in idiopathic acute transverse myelitis (ATM), fractional anisotropy (FA) values would be abnormal not only in the T2-hyperintense lesion but also in the surrounding normal-appearing spinal cord and that the abnormal FA values in the spinal cord could be related to clinical outcome. SUBJECTS AND METHODS: Sagittal diffusion tensor imaging (DTI) was performed in 10 patients with idiopathic ATM (four men, six women; mean age, 45 years; age range, 20-66 years) and 10 sex- and age-matched normal volunteers. FA measurements were made in the spinal cord at three levels: lesion, proximal normal-appearing spinal cord, and distal normal-appearing spinal cord. The grade of FA decrease (mild, less than 10% decrease (FA normal - FA pt) x 100 / FA normal; moderate, 10-20%; severe, more than 20%) was related to the clinical outcome, which was determined by a neurologist using Paine's scale of normal, good, fair, or poor. RESULTS: Mean FA values in patients were significantly lower than those in normal volunteers in lesions (0.5328 vs 0.7125, p = 0.002) and distal normal-appearing spinal cord (0.6676 vs 0.7720, p = 0.0137). All three patients with a mild FA decrease or increase in distal normal-appearing spinal cord showed a normal or good outcome, but all three patients with a severe FA decrease in distal normal-appearing spinal cord showed a fair outcome, among the eight patients to whom steroid treatment was given. CONCLUSION: FA values in lesions and in distal normal-appearing spinal cord significantly decreased in patients with idiopathic ATM, and FA decrease in distal normal-appearing spinal cord might be related to clinical outcome.