Plaque-like demyelination in acute disseminated encephalomyelitis (ADEM) - an autopsy case report

The pattern of demyelination in the scant autopsy literature on acute disseminated encephalomyelitis (ADEM) is described as perivenous sleeves. We report an unusual neuropathological presentation of ADEM, also known as postinfectious or perivenous encephalomyelitis.

A 19-yearold female patient presented with headache and myalgias, followed by subacute onset of lethargy, confusion, left hemiparesis and dysphasia after an interval of 4 - 5 days. On MRI, extensive subcortical white matter lesions were seen and a diagnosis of ADEM was made after other causes were excluded. The patient received intravenous methylprednisolone and plasma exchange. Neurological symptoms remained stable over the length of the hospital stay (1 month). The patient passed away due to non-neurologic causes.

On autopsy, the brain showed extensive, confluent, plaque-like demyelinating lesions with a striking selectivity for the subcortical white matter sparing the U-fibers. No lesions were discernible in the cortex, the deep grey matter, the cerebellum, the spinal cord or the optic nerves on LFB-stained sections. Only one lesion extended to the periventricular area in the right occipital lobe. Some lesions had a scalloped border and foci of inhomogeneous demyelination, suggestion coalescence of smaller lesions. Histologically, all lesions were of the same age, coupling near complete demyelination with relative preservation of axons, along with scant perivascular lymphohistiocytic cuffing, dense infiltration by foamy macrophages, and prominent gliosis.

The morphology of individual demyelinating< lesions is indistinguishable from the lesions in a new onset case of multiple sclerosis (MS) and adds to the autopsy literature on overlapping neuropathological findings in ADEM and multiple sclerosis.