Magnetization transfer and diffusion tensor MR imaging of acute disseminated encephalomyelitis.

BACKGROUND AND PURPOSE: Patients with acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) have a similar pattern of abnormalities on conventional MR images. We used magnetization transfer and diffusion tensor MR imaging to quantify normal-appearing brain tissue and cervical cord disease in patients with ADEM and to compare findings with those in healthy volunteers and patients with MS. METHODS: Brain dual-echo, T1-weighted magnetization transfer, and diffusion tensor images were obtained in eight patients with ADEM, in 10 patients with MS, and in 10 healthy volunteers. Fast short-tau inversion recovery, T1-weighted, and magnetization transfer cervical cord images were also obtained. We identified lesions on the images and quantified their volumes. We performed histogram analysis of the magnetization transfer ratio (MTR) and average mean histogram analysis of the diffusivity (D̅) in normal-appearing brain tissue and MTR in the cervical cord. RESULTS: Histogram analysis of normal-appearing brain tissue in patients with MS showed significantly lower MTRs and peak positions and significantly higher D̅ averages compared with those in patients with ADEM. Patients with MS had significantly lower MTRs and D̅ peak heights and significantly higher average D̅ compared with those in healthy volunteers. Between patients with ADEM and control subjects, normal-appearing brain tissue MTR and D̅ histogram metrics did not differ significantly. Cervical cord MTRs did not differ between control subjects and patients with ADEM, whereas the average MTR and histogram peak position was significantly lower in patients with MS than in the other groups. CONCLUSION: Outside the acute phase of disease and as opposed to what happens in MS, the normal-appearing brain tissue and cervical cord in patients with ADEM are spared in the pathologic process.