Acute Disseminated Encephalomyelitis

Clinical History: A 45-year-old patient presented with history of irritability, drowsiness, hemiparesis, ataxia and fever for one week. Patient was advised to undergo brain MRI with contrast.

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Figure 1a. T2 Flair images show hyperintense lesions in left frontal, right basal ganglia left side of brainstem and b/l occipital regions.

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Figure 1b

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Figure 1c

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Figure 1d

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Figure 2a. DWI images show bright signal in some of these lesions.

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Figure 2 b

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Figure 3a. TIW contrast scan shows enhancement in some of lesions.

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Figure 3b.

MRI findings showed multiple abnormal hyperintense foci in midbrain on left, left frontal, right basal ganglia and b/l occipital regions on flair images (Figure 1). Some of these lesions were bright on DWI (Figure 2) and postcontrast images show enhancement in some of the lesions (Figure 3).

Diagnosis: Acute disseminated encephalomyelitis (ADEM).

Discussion: ADEM is an immune mediated disease of the brain. It usually occurs following a viral infection but may appear following vaccination, bacterial or parasitic infection, or even appear spontaneously. As it involves autoimmune demyelination, it is similar to multiple sclerosis, and is considered part of the multiple sclerosis borderline diseases. The incidence rate is about eight per 1,000,000 people per year. Although it occurs in all ages, most reported cases are in children and adolescents, with the average age around five to eight years old. The mortality rate may be as high as five percent, however full recovery is seen in 50 to 75% of cases with increase in survival rates up to 70 to 90% with figures including minor residual disability as well. The average time to recover is one to six months.

ADEM produces multiple inflammatory lesions in the brain and spinal cord, particularly in the white matter. Usually these are found in the subcortical and central white matter and cortical gray-white junction of both cerebral hemispheres, cerebellum, brainstem, and spinal cord, but periventricular white matter and gray matter of the cortex, thalami and basal ganglia may also be involved.

When the patient suffers more than one demyelinating episode, it is called recurrent disseminated encephalomyelitis or multiphasic disseminated encephalomyelitis (MDEM).

Harpreet Singh, MD, JP Scan Private Diagnostic Center, Khanna, Punjab, India