Background: The concurrence of multiple sclerosis (MS) and glioma is uncommon. Approximately 30 cases have been reported, but in only six of them the tumour was pure or mixed oligodendroglioma. The appearance of new neurological symptoms and signs in a patient with multiple sclerosis is usually attributed to a relapse of this disease and neuroradiological studies are not always performed. When done, the finding of a new focal mass lesion is usually interpreted as a pseudotumoural plaque.
Case report: A 37-year-old man was admitted because of partial simple seizures and an enlarging intracranial mass. He had been diagnosed of MS eleven years earlier. A MRI study performed eight years before admission showed a large mass in the right frontal lobe which was thought to be a pseudotumoural plaque. Two years later, he developed simple partial motor seizures that were initially controlled with valproic acid. He remained well until three months before admission, when seizures reappeared with a poor response to valproic acid. A new MRI study showed an heterogeneous right frontal enlarging mass lesion. A primary neoplasm was suspected and a subtotal removal was performed. The pathological diagnosis was oligodendroglioma with a periferic demyelinating area.
Conclusion: Atypical MRI lesions in a patient with MS must be carefully interpreted. Pseudotumoural plaques have been described both clinically and radiologically to be hardly distinguishable from a tumoural lesion and histological confirmation is often required. The association between MS and glioma is uncommon but it must be kept in mind when a mass lesion develops in a patient with MS.