Clinical manifestation of glioma before computed tomographic appearance: the dilemma of a negative scan.

Eight cases are presented to summarize our experience with patients initially evaluated for the new onset of either seizure activity or focal transient neurological deficits. Each was found to have a normal computed tomographic (CT) scan with and without iodinated contrast infusion. All subsequently returned with a CT scan indicative of a glioma 2 weeks to 39 months later. The apparent reasons for the difficulty in early diagnosis of glioma in certain instances are discussed. A review of the literature with an analysis of the conglomerate data is presented. These cases probably represent a subset of gliomas undergoing anaplastic dedifferentiation from relatively benign to more malignant forms. Recommendations for clinical and radiographic follow-up are outlined.