Presentation
Seizures in the setting of acute renal impairment.
Patient Data
Bifrontal hypoattenuation with patchy enhancement.
There are least four focal regions of signal abnormality. The largest region of signal abnormality involves the bilateral anterior frontal lobes in a near symmetric pattern. The cortex appears essentially spared with enhancement centered on the juxtacortical and subcortical white matter. Multiple punctate regions of hemorrhage are seen embedded within the frontal lobe abnormality. CBV is not elevated. MRS demonstrates elevation of choline and lactate (not shown).
The other abnormal regions of T2 FLAIR hyperintensity and enhancement are very similar in imaging characteristics and also appear to involve the juxtacortical white matter including the left anterior temporal lobe, right mesial temporal lobe and right parietal lobe/postcentral gyrus. These regions are not clearly connected by T2 FLAIR signal change. No extra-axial abnormality. Ventricles and basal cisterns are normal in appearance.
Conclusion:
Overall, in the absence of significant prior illness/immunosuppression/ immune reconstitution, findings are most compatible with an acute monophasic demyelinating disease - acute disseminated encephalomyelitis (ADEM) or (given the hemorrhages) acute hemorrhagic leukoencephalitis.
Given CBV and ADC features, mulitcentric glioma or lymphoma are thought much less likely.
The patient went on to have a right frontal lobe brain biopsy.
Histology:
The biopsies comprise predominantly fragments of unremarkable cerebral cortex with a small amount of underlying white matter. Within the white matter there is widening of perivascular spaces and these are filled with moderate numbers of predominantly CD8+ T lymphocytes. Small numbers of CD4+ T cells and moderate numbers of CD68+ monocyte-macrophages are also present. CD8+ T cells are also scattered throughout white matter. There is prominent microglial activation. There is reduced density of myelin in white matter adjacent to post-capillary venules with mild myelin loss. Vessels are viable and there is no neutrophil polymorphonuclear inflammatory cell infiltration and no hemorrhages are seen. No organisms are identified. Immunostaining for SV40/BKV is negative. There is no evidence of tumor.
Final diagnosis: The features are consistent with acute disseminated encephalomyelitis (ADEM).
Repeat MRI 5 months later (multiple intervening MRI studies were obtained but are not shown) demonstrates marked Improvement of all abnormalities.
Case Discussion
Acute disseminated encephalomyelitis (ADEM) is uncommon in adults but needs to be remembered as a possible diagnosis to avoid unnecessarily aggressive surgery and/or treatment.
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