Acute disseminated encephalomyelitis (ADEM)

Case contributed by Assoc Prof Frank Gaillard


Young woman presenting with progressive left hemiparesis. Respiratory viral infection a week earlier.

Patient Data

Age: 30
Gender: Female

Selected images from an initial MRI (unfortunately the entire study is no longer available) demonstrating numerous white matter lesion with high T2/FLAIR signal, and peripheral incomplete (open-ring) enhancement, and restricted diffusion along the enhancing rim. 

The patient was treated with steroids and rapidly improved clinically. She returned for further imaging 3 weeks later. 

MRI 3 weeks after admission


Comparison has been made to previous MRI scans from 3 weeks earlier. Almost all of the previously demonstrated to the lesions have markedly reduced in size, with the exception of a white matter lesion in the posterior aspect of the left frontal lobe, which was present on previous scans, but has enlarged. It has the same appearances at the previous lesions (C-shaped enhancing rim, open towards the ventricle, central high T2 low T1 signal, which does not attenuate on FLAIR, and restricted diffusion at the enhancing rim). This lesion is immediately below the pre-central gyrus.

MRI 2 weeks later


Comparison has been made to previous imaging. All the large previously demonstrated lesions have a least somewhat reduced in size. The largest lesion, adjacent to the lateral ventricle on the left, beneath the motor strip remains by far the largest, and has only marginally reduced in size, but has reduced significantly in contrast enhancement.

Immediately posterior to this lesion, too small focal regions of high T2 signal measuring 4mm and 7mm respectively have increased when compared to previous scan, although both were previously visible also. These demonstrate restricted diffusion, and the more posterior of the two, contrast enhancement which has also increased.

MRS demonstrated increased Choline, decreased NAA, with increased lipids and lactate.


MRI 2 weeks later still


Significant improvement in the size and conspicuity of lesions with no new lesions evident. 

MRI 5 years later


MRI follow-up is now available for over 5 years, and demonstrates no new lesions, with some residual abnormal T2 signal in the deep and periventricular white matter. 

Case Discussion

This case demonstrates typical imaging features of ADEM, which although characterized as a

monophasic illness, individual lesions are not all at the same stage of evolution, thus some small or inapparent lesions early on can be seen to appear and mature even while other lesions regress. Additonally, relapsing forms of ADEM are certainly described (Relapsing disseminated encephalomyelitis (RDEM), and Multiphasic disseminated encephalomyelitis (MDEM)) although the demarcation between these and multiple sclerosis is contentious.

Importantly, this patient did not have relapsing / remitting long term course. 

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