Meningeal inflammation and demyelination in a patient clinically diagnosed with acute disseminated encephalomyelitis.

Acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) are both CNS inflammatory demyelinating diseases with overlapping clinical features. A case is reported of a 51-year-old female who presented with headache, progressive aphasia and hemiparesis without preceding infection or vaccination. Brain MRI revealed multiple, often confluent, subcortical white matter lesions without enhancement, affecting predominantly the left cerebral hemisphere. CSF examination failed to reveal oligoclonal bands. Brain biopsy revealed both pathological features of ADEM and findings are consistent with the early stage of MS, including meningeal B and T lymphocytic infiltration, perivenular demyelination, subpial demyelination and discrete confluent plaque-like foci of demyelination. Steroid treatment resulted in remarkable clinical and radiological improvement and there has been no recurrence in six years of follow-up. This case highlights the difficulties in differentiating between ADEM and the first attack of MS and further suggests that ADEM and the early stage of MS, and its tumefactive variant, may have a common underlying pathologic mechanism, which may have a therapeutic implication in treating these diseases.