Short case...Acute disseminated encephalomyelitis

1. Short case publication... version 1.8 | Edited by professor Yasser Metwally | January 2008
Short case
Edited by
Professor Yasser Metwally
Professor of neurology
Ain Shams university school of medicine
Cairo, Egypt
Visit my web site at:
http://yassermetwally.com
A 18 years old female patient presented clinically with disturbed level of consciousness, recurrent grand mal
fits, bilateral optic neuritis and meningeal irritation signs. The patient gradually improved during hospital stay
and was discharged two weeks following admission after almost full recovery.
DIAGNOSIS: ACUTE DISSEMINATED ENCEPHALOMYELITIS

2. Figure 1. Acute disseminated encephalomyelitis (ADEM). Postcontrast MRI T1 images showings scattered
hypointense rounded and oval lesions, mostly situated at the junction of deep cortical gray and subcortical white
matter. The immediate periventricular region is spared. Lesions are mostly larger than MS lesions and did not
show contrast enhancement. Some lesions are seen encroaching upon the cortical grey matter. In general lesions
did not have marked mass effect.
Figure 2. Acute disseminated encephalomyelitis (ADEM). Postcontrast MRI T1 images showings scattered
hypointense rounded and oval lesions, mostly situated at the junction of deep cortical gray and subcortical white
matter. The immediate periventricular region is spared. Lesions are mostly larger than MS lesions and did not
show contrast enhancement. Some lesions are seen encroaching upon the cortical grey matter. In general lesions
did not have marked mass effect.

3. Figure 3. A case of acute disseminated encephalomyelitis. Notice that the multifocal cortical / subcortical
hyperintense foci are sparing the periventricular region, and this is the classic pattern in ADEM. The foci, although
of large size they have mild mass effect.
Figure 4. Acute disseminated
encephalomyelitis (ADEM).
Notice that the multifocal cortical
/ subcortical lesions are sparing
the periventricular region. The
ADEM lesions are hypointense on
MRI T1 images and hyperintense
on MRI T2 and FLAIR images.
ADEM lesions, though large,
exert mild mass effect

4. Figure 5. Acute disseminated
encephalomyelitis (ADEM). Notice that
the multifocal cortical / subcortical
lesions are sparing the periventricular
region. The ADEM lesions are
hypointense on MRI T1 images and
hyperintense on MRI T2 and FLAIR
images. ADEM lesions, though large,
exert mild mass effect.
DIFFERENTIAL DIAGNOSIS
In the absence of specific biological markers, the diagnosis of ADEM is based upon clinical and imaging features. Clinical
evaluation, neuroimaging, and blood and CSF analysis can help to distinguish ADEM from other conditions. [1] Herpes
simplex encephalitis commonly presents with abnormal behavior and focal/secondary generalized seizures, which are
more frequent and difficult to treat than in ADEM. MRI, EEG, and CSF polymerase chain reaction for Herpes simplex
virus help in confirmation of the diagnosis. Japanese encephalitis presents with acute encephalopathy. MRI may show
bilateral thalamic lesions, akin to ADEM. History, EEG findings, and CSF evidence of antibodies to the virus are useful
for differentiation. Other infections such as bacterial meningitis and brain abscess can be ruled out by relevant
investigations such as imaging and lumbar puncture. Complicated tuberculous meningitis may sometimes mimic ADEM
and can be excluded if CSF sugar is normal and cultures are sterile.
Neuromyelitis optica is characterized by optic neuritis and myelitis, with spinal lesions extending over three or more
segments, features that may also be seen in ADEM. It may be distinguished from ADEM by the relative paucity of white
matter lesions in MRI of the brain and presence of antibodies to aquaporin 4 (NMO-IgG). [1] Patients with Behcet's
disease may present with multifocal neurological signs due to brain and spinal cord involvement. Clinical and imaging
features may resemble ADEM, and the history of recurrent mucocutaneous ulcers of the mouth and genitalia will be
essential to establish the diagnosis. Antiphospholipid antibody syndrome may also mimic the clinical and MRI features of
ADEM and should be ruled out by measuring the specific antibodies. Immune-mediated disorders such as systemic lupus
erythematosus, Sjögren syndrome, and sarcoidosis may present with neurological dysfunction and multifocal white matter
changes and can be diagnosed by history and relevant blood tests. Susac's syndrome may present with subacute

5. encephalopathy, with MRI of the brain showing multiple white matter lesions; however, it can be differentiated from
ADEM based on additional features such as the presence of headache, visual impairment due to retinal artery branch
occlusion, sensorineural hearing loss, and specific involvement of central corpus callosum in MRI. [1] The diagnosis of
recurrent ADEM should be made only after excluding other lesions such as arteriovenous malformations, neoplasms, and
vasculitis.
Metabolic leukoencephalopathies such as metachromatic leukodystrophy (MLD), adrenoleukodystrophy, and MELAS
(mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) may mimic childhood ADEM.
Leukodystrophies may have a stepladder clinical course, with the exacerbations associated with febrile illnesses. History
may reveal prior neurological dysfunction. MRI may show symmetric, confluent white matter lesions, hallmarks of
inherited rather than acquired leukoencephalopathies. Specific investigations such as serum aryl sulfatase for MLD and
very long-chain fatty acids (VLCFA) levels for adrenoleukodystrophy will confirm the diagnosis. The clinical features of
mitochondrial cytopathies such as MELAS may be similar to that of ADEM and lesions seen on MRI may be transient.
Serum and CSF lactate levels may be elevated during the acute episode and MR spectroscopic imaging may show
elevated lactate in the affected tissues. [1]
ADEM or multiple sclerosis?
In a patient presenting with neurological dysfunction and MRI showing multiple white matter lesions, the most important
differential diagnosis is MS. Distinguishing between ADEM and MS is a diagnostic challenge and has important
therapeutic and prognostic implications. There are several clinical, imaging, and laboratory parameters that may be useful
to distinguish between the two. CSF electrophoresis has shown a significant reduction in the beta-1 globulin fraction in
patients with MS as compared to those with ADEM and this may be a potential CSF marker. [1] Features that strongly
favor ADEM include a history of preceding infection, polysymptomatic neurological dysfunction, encephalopathy, grey
matter involvement on MRI, and absence of oligoclonal bands in CSF. Often, distinction between these two conditions
cannot be made with certainty and follow-up with serial MRI may be necessary to establish the diagnosis.
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References
1. Metwally, MYM: Textbook of neurimaging, A CD-ROM publication, (Metwally, MYM editor) WEB-CD agency
for electronic publishing, version 9.1a January 2008