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.